Advertisement

Factors Used to Determine Return to Unrestricted Sports Activities After Anterior Cruciate Ligament Reconstruction

      Purpose

      Anterior cruciate ligament (ACL) reconstruction is commonly performed in athletes, with the goal of return to sports activities. Unfortunately, this operation may fail, and the rates of either reinjuring an ACL-reconstructed knee or sustaining an ACL rupture to the contralateral knee range from 3% to 49%. One problem that exists is a lack of information and consensus regarding the appropriate criteria for releasing patients to unrestricted sports activities postoperatively. The purpose of this study was to determine the published criteria used to allow athletes to return to unrestricted sports activities after ACL reconstruction.

      Methods

      A systematic search was performed to identify the factors investigators used to determine when return to athletics was allowed after primary ACL reconstruction. Inclusion criteria were English language, publication within the last 10 years, clinical trial, all adult patients, primary ACL reconstruction, original research investigation, and minimum 12 months' follow-up.

      Results

      Of 716 studies identified, 264 met the inclusion criteria. Of these, 105 (40%) failed to provide any criteria for return to sports after ACL reconstruction. In 84 studies (32%) the amount of time postoperatively was the only criterion provided. In 40 studies (15%) the amount of time along with subjective criteria were given. Only 35 studies (13%) noted objective criteria required for return to athletics. These criteria included muscle strength or thigh circumference (28 studies), general knee examination (15 studies), single-leg hop tests (10 studies), Lachman rating (1 study), and validated questionnaires (1 study).

      Conclusions

      The results of this systematic review show noteworthy problems and a lack of objective assessment before release to unrestricted sports activities. General recommendations are made for quantification of muscle strength, stability, neuromuscular control, and function in patients who desire to return to athletics after ACL reconstruction, with acknowledgment of the need for continued research in this area.

      Level of Evidence

      Level IV, systematic review of Level I to IV studies.
      Anterior cruciate ligament (ACL) tears are the most common, complete ligamentous injuries that occur in the knee joint. In the United States, ACL tears occur in an estimated 1 in 3,500 individuals each year,
      • Baer G.S.
      • Harner C.D.
      Clinical outcomes of allograft versus autograft in anterior cruciate ligament reconstruction.
      and although exact data are not currently available, it is believed that approximately 125,000 to 200,000 ACL reconstructions are performed annually. Most patients who sustain ACL injuries and undergo reconstruction are athletes aged under 25 years who are frequently involved in high school, collegiate, or league sports. The goals of this operation for these individuals are to stabilize the knee to prevent future reinjuries and allow a safe return to their previous level of activity.
      The published long-term rates of either reinjuring an ACL-reconstructed knee or sustaining an ACL rupture on the contralateral knee on return to activities after surgery vary widely (Table 1). Authors have investigated possible factors to account for reinjuries including young patient age, high sports activity level, prior meniscectomy, and improper graft placement. ACL reconstructions may also fail for reasons other than a traumatic reinjury. These include errors in surgical technique (improper placement of the ACL graft, use of low-strength grafts, inadequate fixation, graft impingement in the notch, or excessive or insufficient graft tensioning at surgery); failure of graft integration, tendon-to-bone healing, or remodeling; lateral, posterolateral, or medial ligament deficiency; postoperative infection; and inadequate rehabilitation.
      Table 1Risks of Reinjury to ACL-Reconstructed Knee and Injury to ACL in Contralateral Knee in Clinical Studies
      Lead Author (yr), JournalNo. of PatientsFollow-upACL GraftReinjuredRevisedFully Positive Pivot Shift, Lachman, and IKDC Grade C-DInjured ACL Contralateral KneeOverall ACL Reinjury Rate
      Includes reinjuries to either knee, ACL revision, IKDC grades C or D for pivot-shift test, and Lachman test.
      Factors Statistically Associated with Reinjuries, Graft Failures
      Hui (2011),
      • Hui C.
      • Salmon L.J.
      • Kok A.
      • Maeno S.
      • Linklater J.
      • Pinczewski L.A.
      Fifteen-year outcome of endoscopic anterior cruciate ligament reconstruction with patellar tendon autograft for “isolated” anterior cruciate ligament tear.
      AJSM
      9015 yrBPTB autograft8%8%8%24%30%Coronal graft inclination angle < 17° (vertical graft placement) for ACL-reconstructed knee. Age < 18 years for contralateral knee
      Shelbourne (2009),
      • Shelbourne K.D.
      • Gray T.
      • Haro M.
      Incidence of subsequent injury to either knee within 5 years after anterior cruciate ligament reconstruction with patellar tendon autograft.
      AJSM
      1,4155 yrBPTB autograft4.3%NANA5.3%9.6%Age < 18 years and participation in basketball or soccer for either knee. Female gender for contralateral knee
      Nakata (2008),
      • Nakata K.
      • Shino K.
      • Horibe S.
      • et al.
      Arthroscopic anterior cruciate ligament reconstruction using fresh-frozen bone plug-free allogeneic tendons: 10-year follow-up.
      Arthroscopy
      6810 yrAllogeneic free tendon5%5%8%6%16%None
      Pinczewski (2007),
      • Pinczewski L.A.
      • Lyman J.
      • Salmon L.J.
      • Russell V.J.
      • Roe J.
      • Linklater J.
      A 10-year comparison of anterior cruciate ligament reconstructions with hamstring tendon and patellar tendon autograft: A controlled, prospective trial.
      AJSM
      18010 yrBPTB autograft in 90 patients8%NA8%22%27%Increased laxity for ACL-reconstructed knees. Age < 21 years for contralateral knee
      STG autograft in 90 patients13%13%10%
      Keays (2007),
      • Keays S.L.
      • Bullock-Saxton J.E.
      • Keays A.C.
      • Newcombe P.A.
      • Bullock M.I.
      A 6-year follow-up of the effect of graft site on strength, stability, range of motion, function, and joint degeneration after anterior cruciate ligament reconstruction: Patellar tendon versus semitendinosus and gracilis tendon graft.
      AJSM
      516 yrBPTB autograft in 29 patients0%0%0%7%7%None
      STG autograft in 27 patients7%0%7%11%18%
      Salmon (2006),
      • Salmon L.J.
      • Russell V.J.
      • Refshauge K.
      • et al.
      Long-term outcome of endoscopic anterior cruciate ligament reconstruction with patellar tendon autograft: Minimum 13-year review.
      AJSM
      675-13 yrBPTB autograft13%13%7%22%40%Age < 21 years and meniscectomy for ACL-reconstructed knee
      Drogset (2006),
      • Drogset J.O.
      • Grøntvedt T.
      • Robak O.R.
      • Mølster A.
      • Viset A.T.
      • Engebretsen L.
      A sixteen-year follow-up of three operative techniques for the treatment of acute ruptures of the anterior cruciate ligament.
      JBJS
      12916 yrPrimary repair in 45 patientsNA24%51%2%49%None
      Repair + LAD in 42 patientsNA10%36%12%43%
      BPTB autograft in 42 patientsNA2%8%12%24%
      Ait Si Selmi (2006),
      • Ait Si Selmi T.
      • Fithian D.
      • Neyret P.
      The evolution of osteoarthritis in 103 patients with acl reconstruction at 17 years follow-up.
      Knee
      10317 yrBPTB autograft + iliotibial band extra-articularNANA40%NA40%None
      Hertel (2005),
      • Hertel P.
      • Behrend H.
      • Cierpinski T.
      • Musahl V.
      • Widjaja G.
      ACL reconstruction using bone-patellar tendon-bone press-fit fixation: 10-year clinical results.
      KSSTA
      969-12 yrBPTB autograftNANA3%NA3%None
      Mykelbust (2003),
      • Myklebust G.
      • Holm I.
      • Maehlum S.
      • Engebretsen L.
      • Bahr R.
      Clinical, functional, and radiologic outcome in team handball players 6 to 11 years after anterior cruciate ligament injury: A follow-up study.
      AJSM
      576-11 yrBPTB autograft19%19%NA11%30%Return to team handball
      Abbreviations: AJSM, The American Journal of Sports Medicine; BPTB, bone–patellar tendon–bone; IKDC, International Knee Documentation Committee; JBJS, Journal of Bone and Joint Surgery (American Version); KSSTA, Knee Surgery, Sports Traumatology, Arthroscopy; LAD, ligament augmentation device; NA, not available; STG, semitendinosus-gracilis.
      low asterisk Includes reinjuries to either knee, ACL revision, IKDC grades C or D for pivot-shift test, and Lachman test.
      Postoperative rehabilitation plays a critical role in returning patients to athletic or demanding occupational activities as safely as possible. Few studies have assessed the effectiveness of specific rehabilitation protocols with regard to restoring normal muscle strength, balance, proprioception, and other neuromuscular indices required for high-risk activities such as cutting, twisting, and pivoting. Importantly, there exist many questions and a lack of consensus regarding the appropriate criteria for releasing patients to unrestricted sports activities postoperatively.
      The purpose of this systematic review was to examine the factors investigators have used over the last 10 years to determine when return to unrestricted athletics is appropriate postoperatively. To our knowledge, no such systematic review has been conducted on this topic to date.

      Methods

      Literature Search

      We searched Medline for all published literature from April 2001 to April 2011 using the following key words: anterior cruciate ligament reconstruction, ACL reconstruction, ACL reconstruction rehabilitation, and ACL reconstruction results. We also conducted manual searches of the following journals published during this time period: The American Journal of Sports Medicine; Arthroscopy; The Journal of Bone and Joint Surgery (both the American and British volumes); The Knee; Clinical Orthopaedics and Related Research; and Knee Surgery, Sports Traumatology, Arthroscopy.
      Inclusion criteria were English language, original research report (any level of evidence), primary ACL reconstruction (any graft type), skeletally mature patients, and minimum 12 months' follow-up. Exclusion criteria were revision ACL reconstruction; dislocated knees; major concomitant procedures such as high tibial osteotomy, meniscus allograft, or other knee ligament reconstructions; follow-up of less than 12 months; and other types of articles such as reviews, case reports, abstracts, and technical notes.

      Data Abstraction

      The data from each study that met the inclusion criteria were abstracted for information regarding the type of ACL graft used and whether the following categories were used to release patients to athletic activities: (1) time postoperatively; (2) knee range of motion (ROM) and knee effusion; (3) stability, as indicated by knee arthrometer testing or results of Lachman or pivot-shift testing; (4) muscle strength testing (hamstring, quadriceps, hip, core) or thigh circumference measurement; (5) dynamic function with single-leg hop tests; (6) neuromuscular function with drop-jump tests; (7) aerobic capacity assessment for maximal oxygen uptake; (8) sports-specific testing that included results required to return to competition; and (9) validated questionnaire results.

      Results

      Literature Search

      Our search initially identified 716 articles, of which 452 were excluded according to our study criteria. This led to 264 articles appropriate for this review. Of these, 105 (40%) failed to provide any criteria for return to sports after ACL reconstruction (Fig 1) . In the remaining 159 studies, 6 of the 9 categories of return-to-sports criteria that were searched for were found. The number of categories identified per study was 1 in 125 studies, 2 in 19 studies, 3 in 13 studies, 4 in 1 study, and 5 in 1 study.
      Figure thumbnail gr1
      Figure 1Flowchart of ACL reconstruction studies with criteria for return to athletics.

      Time Postoperatively

      Of the 264 studies, 158 (60%) listed the amount of time postoperatively that patients were allowed to return to sports activities (Table 2). In 84 studies (32%) the amount of time postoperatively was the only criterion provided. In 40 other studies (15%), the amount of time along with subjective criteria (that could not be measured) was given (Table 3). Only 35 studies (13%) noted objective criteria required for return to athletics (Table 4). All but 1 of these 35 studies also provided criteria for time postoperatively.
      Table 2Time Allowed Postoperatively for Return to Sports According to Graft Type
      No. of Studies
      Time PostoperativelyBPTB AutograftSTG AutograftQT AutograftDouble-Bundle GraftsOther Grafts
      Allografts, primary repair, or synthetic ligaments.
      Total
      ≥12 wk111
      3-4 mo1212
      4 mo22
      4-5 mo1112
      4-6 mo1314
      >4 mo223
      ≥5 mo133
      5-6 mo2112
      ≥6 mo4551584984
      6-7 mo111
      6-8 mo324
      6-9 mo53228
      6-10 mo25125
      6-12 mo11
      7-9 mo111
      ≥8 mo234
      8-9 mo22
      ≥9 mo410211
      9-10 mo112
      9-12 mo22
      10 mo11
      10-11 mo111
      10-12 mo31124
      ≥12 mo44228
      Abbreviations: BPTB, bone–patellar tendon–bone; QT, quadriceps tendon; STG, semitendinosus-gracilis.
      NOTE. There were multiple grafts observed in 54 of the 158 studies that provided criteria for time postoperatively.
      low asterisk Allografts, primary repair, or synthetic ligaments.
      Table 3Subjective Criteria Provided for Release to Sports Activities
      CriteriaNo. of Studies
      Good firm anterior tibial stop1
      Good firm point on clinical evaluation1
      Knee stability confirmed on clinical examination3
      Stable knee1
      Good stability1
      Normal laxity of knee1
      Satisfactory stability1
      Ability to pass sports-specific tests such as cutting, squatting, and jumping1
      Knee function normal or nearly normal on clinical examination1
      Satisfactory clinical examination1
      Confirmation of recovery of quadriceps strength2
      Functional quadriceps control1
      Sufficient muscle recovery after specified athletic training accomplished1
      Depending on functional capacity2
      Good recovery of ROM, muscle strength, and stability1
      Regained full subjective functional stability5
      Regained full functional stability9
      Regained full functional strength and stability2
      Full functional stability in terms of strength, coordination, and balance3
      No significant side-to-side deficits
      If all parameters met1
      Depending on individual progress1
      After ACL accelerated rehabilitation program1
      No problematic symptoms in knee joint1
      Only after rehabilitation goals met1
      Controlled functional training had been performed without difficulty2
      Good muscle coordination in agility training and balance equal to opposite side1
      If patient's rehabilitation of limb and stability warrant1
      Satisfactory performance on agility drills1
      Depending on functional ability, including run-to-sprint intervals, sidestep cutting, and timed recreational drills1
      Close to full ROM and muscle strength1
      NOTE. Multiple subjective criteria were given in 10 of the 40 studies included.
      Table 4Objective Criteria Provided for Release to Sports Activities
      Criteria CategoriesNo. of Studies
      Time postoperatively, muscle strength16
      Time postoperatively, muscle strength, ROM/effusion3
      Time postoperatively, thigh circumference, single-leg hop test3
      Time postoperatively, ROM/effusion4
      Time postoperatively, muscle strength, single-leg hop test2
      Time postoperatively, muscle strength, ROM2
      Time postoperatively, Lachman rating, effusion1
      Time postoperatively, muscle strength/thigh circumference, single-leg hop test1
      Time postoperatively, muscle strength, single-leg hop test, ROM/effusion1
      Time postoperatively, muscle strength, 4 single-leg hop tests, ROM/effusion, validated questionnaires1
      Single-leg hop test1
      NOTE. Data are presented for 35 studies that provided objective criteria for return to sports.
      There appeared to be no effect of the type of graft on the time sports could be resumed postoperatively. Although there was high variability among the investigations (ranging from ≥12 weeks to ≥12 months), 84 studies listed 6 months or greater as the time period allowed for return to athletics.

      Muscle Strength

      Of the 264 studies, 25 (9%) reported muscle strength criteria (Table 5) required for return to athletics. Recommendations ranged from greater than 80% to greater than 90% for isokinetic testing of the quadriceps and hamstrings compared with the contralateral side. We were unable to find data regarding the hamstring-quadriceps ratio or other muscle groups in our review. Three other studies noted that thigh circumference measurements of less than 1 cm or less than 0.5 cm (difference between limbs) were required for return to athletics.
      Table 5Muscle Strength Criteria for Return to Sports According to Graft Type
      Muscle Strength Criteria (Compared With Opposite Side)No. of Studies
      BPTB AutograftSTG AutograftDouble-Bundle GraftsOther Grafts
      Allografts or BPTB plus ligament augmentation device.
      Total
      >90% isokinetic strength952111
      ≥85% isokinetic strength33237
      >80% isokinetic strength23015
      ≥90% quadriceps index03011
      ≥90% weighted leg extension10011
      NOTE. There were multiple grafts observed in 15 of the 25 studies that provided muscle strength criteria.
      Abbreviations: BPTB, bone–patellar tendon–bone; STG, semitendinosus-gracilis.
      low asterisk Allografts or BPTB plus ligament augmentation device.

      General Knee Examination

      Effusion and/or ROM criteria were listed in 15 studies (6%): 11 listed both factors, 2 provided effusion criteria only, and 2 listed ROM criteria only. In all studies no effusion and a full ROM were given as required criteria for return to sports.

      Dynamic Function: Single-Leg Hop Tests

      Single-leg hop testing was included in 10 studies (4%) as a criterion in their assessment for return to sports (Table 6). Six defined a result of greater than 90% of the distance hopped on a single-hop test compared with the opposite side as acceptable. One study noted that 90% or greater was required on 4 hop tests: single hop, triple hop, triple crossover hop, and timed hop.
      • Hartigan E.H.
      • Axe M.J.
      • Snyder-Mackler L.
      Time line for noncopers to pass return-to-sports criteria after anterior cruciate ligament reconstruction.
      Table 6Single-Leg Hop Test Criteria for Return to Sports According to Graft Type
      Single-Leg Hop Test Criteria (Compared With Opposite Side)No. of Studies
      BPTB AutograftSTG AutograftDouble-Bundle GraftsOther Grafts
      Allografts.
      Total
      >90% single hop43116
      ≥90% on 4 tests: single hop, triple hop, crossover hop, and timed hop01011
      ≥85% single hop02022
      >90% “hop/jump testing”10011
      NOTE. There were multiple grafts observed in 7 of the 10 studies that provided single-leg hop test criteria.
      Abbreviations: BPTB, bone–patellar tendon–bone; STG, semitendinosus-gracilis.
      low asterisk Allografts.

      Stability

      Only 1 study provided objective knee stability criteria (negative Lachman test), although 7 other studies noted subjective stability criteria (Table 4). In 1 other study, the results of knee arthrometer testing determined whether a brace was required when patients returned to sports activities.

      Validated Questionnaire

      Only 1 study included data from validated questionnaires in its criteria for return to sport. In that investigation a score of 90% or greater was required on the Knee Outcome Survey activities-of-daily-living scale and on the global rating of an overall knee function scale for release to full athletics.

      Discussion

      The primary findings of this systematic review suggest that noteworthy problems and a lack of objective assessment methods exist in the published literature before release to unrestricted sports activities after ACL reconstruction. Only 35 (13%) of the 264 articles reviewed included some measurable objective criteria that patients had to achieve before resuming unrestricted athletics. However, even in those articles, only 1 to 2 criteria other than time postoperatively were included in most of the studies (33).
      The goals of ACL reconstruction in athletes are to restore normal knee joint stability and function and allow a return to sports activities. However, even with modern operative techniques and rehabilitation programs, there is strong evidence that deficits in balance, proprioception, muscle strength, and neuromuscular control exist for many months postoperatively.
      • Hiemstra L.A.
      • Webber S.
      • MacDonald P.B.
      • Kriellaars D.J.
      Contralateral limb strength deficits after anterior cruciate ligament reconstruction using a hamstring tendon graft.
      • Eitzen I.
      • Holm I.
      • Risberg M.A.
      Preoperative quadriceps strength is a significant predictor of knee function two years after anterior cruciate ligament reconstruction.
      • Madhavan S.
      • Shields R.K.
      Neuromuscular responses in individuals with anterior cruciate ligament repair.
      • Orishimo K.F.
      • Kremenic I.J.
      • Mullaney M.J.
      • McHugh M.P.
      • Nicholas S.J.
      Adaptations in single-leg hop biomechanics following anterior cruciate ligament reconstruction.
      Bonfim et al.
      • Bonfim T.R.
      • Paccola C.A.
      • Barela J.A.
      Proprioceptive and behavior impairments in individuals with anterior cruciate ligament reconstructed knees.
      reported sensory and motor deficits in ACL-reconstructed knees with a postoperative period of 12 to 30 months compared with matched controls. Altered knee joint kinematics have been noted 4 to 12 months after ACL reconstruction during single-leg hop landings,
      • Deneweth J.M.
      • Bey M.J.
      • McLean S.G.
      • Lock T.R.
      • Kolowich P.A.
      • Tashman S.
      Tibiofemoral joint kinematics of the anterior cruciate ligament-reconstructed knee during a single-legged hop landing.
      • Gokeler A.
      • Hof A.L.
      • Arnold M.P.
      • Dijkstra P.U.
      • Postema K.
      • Otten E.
      Abnormal landing strategies after ACL reconstruction.
      5 to 12 months postoperatively during downhill running,
      • Tashman S.
      • Kolowich P.
      • Collon D.
      • Anderson K.
      • Anderst W.
      Dynamic function of the ACL-reconstructed knee during running.
      and 3 months postoperatively during a forward lunge
      • Papannagari R.
      • Gill T.J.
      • Defrate L.E.
      • Moses J.M.
      • Petruska A.J.
      • Li G.
      In vivo kinematics of the knee after anterior cruciate ligament reconstruction: A clinical and functional evaluation.
      and walking.
      • Gao B.
      • Zheng N.N.
      Alterations in three-dimensional joint kinematics of anterior cruciate ligament-deficient and -reconstructed knees during walking.
      Some long-term studies,
      • Hui C.
      • Salmon L.J.
      • Kok A.
      • Maeno S.
      • Linklater J.
      • Pinczewski L.A.
      Fifteen-year outcome of endoscopic anterior cruciate ligament reconstruction with patellar tendon autograft for “isolated” anterior cruciate ligament tear.
      • Pinczewski L.A.
      • Lyman J.
      • Salmon L.J.
      • Russell V.J.
      • Roe J.
      • Linklater J.
      A 10-year comparison of anterior cruciate ligament reconstructions with hamstring tendon and patellar tendon autograft: A controlled, prospective trial.
      • Salmon L.J.
      • Russell V.J.
      • Refshauge K.
      • et al.
      Long-term outcome of endoscopic anterior cruciate ligament reconstruction with patellar tendon autograft: Minimum 13-year review.
      as well as a short-term study,
      • Paterno M.V.
      • Schmitt L.C.
      • Ford K.R.
      • et al.
      Biomechanical measures during landing and postural stability predict second anterior cruciate ligament injury after anterior cruciate ligament reconstruction and return to sport.
      have reported high reinjury rates in athletes on return to activity, and the factors most responsible for this problem remain unknown. The contralateral knee is at risk for ACL rupture as well, and some studies have documented a higher rate of this injury than a tear of the ACL-reconstructed knee.
      • Hui C.
      • Salmon L.J.
      • Kok A.
      • Maeno S.
      • Linklater J.
      • Pinczewski L.A.
      Fifteen-year outcome of endoscopic anterior cruciate ligament reconstruction with patellar tendon autograft for “isolated” anterior cruciate ligament tear.
      • Salmon L.J.
      • Russell V.J.
      • Refshauge K.
      • et al.
      Long-term outcome of endoscopic anterior cruciate ligament reconstruction with patellar tendon autograft: Minimum 13-year review.
      • Paterno M.V.
      • Schmitt L.C.
      • Ford K.R.
      • et al.
      Biomechanical measures during landing and postural stability predict second anterior cruciate ligament injury after anterior cruciate ligament reconstruction and return to sport.
      In this systematic review, a multifactorial analysis of knee function was determined by only 2 studies in which 3 to 4 categories (other than time postoperatively) were included for release to sports activities.
      • Hartigan E.H.
      • Axe M.J.
      • Snyder-Mackler L.
      Time line for noncopers to pass return-to-sports criteria after anterior cruciate ligament reconstruction.
      • Mascarenhas R.
      • Tranovich M.
      • Karpie J.C.
      • Irrgang J.J.
      • Fu F.H.
      • Harner C.D.
      Patellar tendon anterior cruciate ligament reconstruction in the high-demand patient: Evaluation of autograft versus allograft reconstruction.
      Hartigan et al.
      • Hartigan E.H.
      • Axe M.J.
      • Snyder-Mackler L.
      Time line for noncopers to pass return-to-sports criteria after anterior cruciate ligament reconstruction.
      required scores of 90% or greater on the quadriceps strength index, 4 single-leg hop tests (single hop, triple hop, triple crossover hop, and timed hop), the Knee Outcome Survey activities-of-daily-living scale, and a global rating of overall knee function for return to sports. They also included less than 1+ knee effusion and full ROM in their assessment. Mascarenhas et al.
      • Mascarenhas R.
      • Tranovich M.
      • Karpie J.C.
      • Irrgang J.J.
      • Fu F.H.
      • Harner C.D.
      Patellar tendon anterior cruciate ligament reconstruction in the high-demand patient: Evaluation of autograft versus allograft reconstruction.
      proposed 90% or greater on a weighted leg extension test, 90% or greater on hop/jump tests (specific tests were not provided), full ROM, and no effusion for return to athletics.
      A few other authors have proposed rigorous testing before return to sports. These were not clinical outcome studies and were therefore not included in our systematic review. Neeter et al.
      • Neeter C.
      • Gustavsson A.
      • Thomeé P.
      • Augustsson J.
      • Thomeé R.
      • Karlsson J.
      Development of a strength test battery for evaluating leg muscle power after anterior cruciate ligament injury and reconstruction.
      developed a test battery to determine quadriceps and hamstring power in ACL-reconstructed knees in both open and closed kinetic chain conditions. They proposed that 90% of muscular power or greater on the reconstructed knee compared with the opposite knee represented a normal result. In their study, 9 of 10 patients who were assessed 6 months after ACL reconstruction had abnormal muscular power compared with healthy controls. Kvist
      • Kvist J.
      Rehabilitation following anterior cruciate ligament injury: Current recommendations for sports participation.
      in 2004 reviewed ACL rehabilitation programs and concluded that the criteria for release to sports activities were unknown. It was noted that many authors decided on the timeline first and developed the rehabilitation program according to that criterion only, which is not a desirable approach. A listing of proposed criteria in that investigation included rehabilitation factors (<10% to 15% deficit muscle strength and single-leg hop test, no pain or effusion, full ROM, functional knee stability evaluated by objective measurements such as motion analysis), surgical factors (static knee stability measured by KT-1000 testing [MEDmetric, San Diego, CA]), and other factors (social factors, psychological factors, associated injuries).
      Van Grinsven et al.
      • van Grinsven S.
      • van Cingel R.E.
      • Holla C.J.
      • van Loon C.J.
      Evidence-based rehabilitation following anterior cruciate ligament reconstruction.
      recently conducted a systematic review of the rehabilitation literature to develop an evidence-based postoperative ACL program that would allow a return to athletics within 6 months. They recommended the following for return-to-sports criteria: full ROM, 85% or greater on strength (quadriceps and hamstrings) and single-leg hop tests compared with the opposite leg, less than 15% deficit on hamstring-quadriceps strength ratio, no pain or swelling with sport-specific activities, and a stable knee in active situations.
      A few authors have assessed certain risk factors associated with reinjury rates, including patient age, sex, sports activity level, type of graft, and meniscectomy. Borchers et al.
      • Borchers J.R.
      • Pedroza A.
      • Kaeding C.
      Activity level and graft type as risk factors for anterior cruciate ligament graft failure: A case-control study.
      found that the use of allografts and a return to high levels of sports activities were significant risk factors for ACL graft failure in 21 of 322 patients followed up 2 years postoperatively. Their criteria for return to play were “good quadriceps control”; no functional complaints; confidence when running, cutting, and jumping at full speed; and 85% or greater on the single-leg hop test. This was the only study that did not provide time postoperatively as an additional criterion; instead, the authors stated that progression was based on the patient achieving functional criteria. Paterno et al.
      • Paterno M.V.
      • Schmitt L.C.
      • Ford K.R.
      • et al.
      Biomechanical measures during landing and postural stability predict second anterior cruciate ligament injury after anterior cruciate ligament reconstruction and return to sport.
      reported that alterations in neuromuscular control of the hip and knee on a drop-jump task and postural stability predicted ACL injury on return to activities after reconstruction in 43 athletes followed up for 1 year postoperatively. They did not provide criteria for return to sports after ACL reconstruction, and in 10 of the 13 patients who had a reinjury, it occurred in the contralateral knee. Patient age of either less than 18 years
      • Hui C.
      • Salmon L.J.
      • Kok A.
      • et al.
      Long-term survival of high tibial osteotomy for medial compartment osteoarthritis of the knee.
      • Shelbourne K.D.
      • Gray T.
      • Haro M.
      Incidence of subsequent injury to either knee within 5 years after anterior cruciate ligament reconstruction with patellar tendon autograft.
      or less than 21 years
      • Pinczewski L.A.
      • Lyman J.
      • Salmon L.J.
      • Russell V.J.
      • Roe J.
      • Linklater J.
      A 10-year comparison of anterior cruciate ligament reconstructions with hamstring tendon and patellar tendon autograft: A controlled, prospective trial.
      • Salmon L.J.
      • Russell V.J.
      • Refshauge K.
      • et al.
      Long-term outcome of endoscopic anterior cruciate ligament reconstruction with patellar tendon autograft: Minimum 13-year review.
      has been cited by other authors as a risk factor for reinjuries. Return to high-risk sports such as soccer,
      • Shelbourne K.D.
      • Gray T.
      • Haro M.
      Incidence of subsequent injury to either knee within 5 years after anterior cruciate ligament reconstruction with patellar tendon autograft.
      basketball,
      • Shelbourne K.D.
      • Gray T.
      • Haro M.
      Incidence of subsequent injury to either knee within 5 years after anterior cruciate ligament reconstruction with patellar tendon autograft.
      and team handball
      • Myklebust G.
      • Holm I.
      • Maehlum S.
      • Engebretsen L.
      • Bahr R.
      Clinical, functional, and radiologic outcome in team handball players 6 to 11 years after anterior cruciate ligament injury: A follow-up study.
      has also been noted to be associated with higher injury rates. Unfortunately, studies that have assessed factors that may be responsible for reinjury rates have not taken into account the status of the athletes' strength, stability, neuromuscular control, and general knee condition on return to sports. The possibility exists that many athletes have not regained acceptable levels of function in these categories in both lower limbs and that the premature release to unrestricted activities may be a factor for the subsequent reinjuries.
      Postoperative rehabilitation plays a critical role in returning patients to athletic activities as safely as possible. In discussing their high rate of reinjury after ACL reconstruction, Salmon et al.
      • Salmon L.J.
      • Russell V.J.
      • Refshauge K.
      • et al.
      Long-term outcome of endoscopic anterior cruciate ligament reconstruction with patellar tendon autograft: Minimum 13-year review.
      noted that a motor-retraining rehabilitation program was worthy of future study, even though they did not allow a return to sports until 9 months postoperatively. Risberg and Holm
      • Risberg M.A.
      • Holm I.
      The long-term effect of 2 postoperative rehabilitation programs after anterior cruciate ligament reconstruction: A randomized controlled clinical trial with 2 years of follow-up.
      concluded that the combination of strength training and neuromuscular exercises was required to achieve the best outcomes, including the patient's perception of knee function and knee performance on strength and hop tests. Future studies are required to determine whether advanced rehabilitation programs that include neuromuscular retraining are effective in reducing the reinjury rate after surgery.
      Reducing the risk of reinjury after ACL reconstruction on return to athletics requires a multifaceted approach. The reconstructive procedure itself is of paramount importance, because a nonanatomic or vertically placed graft has a high risk of failure even without return to strenuous activities.
      • Marchant B.G.
      • Noyes F.R.
      • Barber-Westin S.D.
      • Fleckenstein C.
      Prevalence of nonanatomical graft placement in a series of failed anterior cruciate ligament reconstructions.
      The postoperative physical therapy program should be structured and gradually intensified to be effective without causing complications such as anterior knee pain or tendinitis (Video 1, available at www.arthroscopyjournal.org). In addition, consideration is required of any major concomitant procedures such as meniscus repairs, which require modifications to the protocol. Advanced neuromuscular retraining should be accomplished along with strength training before return to high-risk activities.
      • Risberg M.A.
      • Holm I.
      The long-term effect of 2 postoperative rehabilitation programs after anterior cruciate ligament reconstruction: A randomized controlled clinical trial with 2 years of follow-up.
      • Risberg M.A.
      • Holm I.
      • Myklebust G.
      • Engebretsen L.
      Neuromuscular training versus strength training during first 6 months after anterior cruciate ligament reconstruction: A randomized clinical trial.
      Finally, we believe that factors related to muscle strength, stability, neuromuscular control, and lower limb function should be measured before release to unrestricted activities. Our criteria for release include less than 10% deficit in strength of the quadriceps and hamstring on isokinetic testing at 180°/s and 300°/s, less than 15% deficit in lower limb symmetry on single-leg hop testing (single hop, triple hop, crossover hop, and timed hop
      • Noyes F.R.
      • Barber S.D.
      • Mangine R.E.
      Abnormal lower limb symmetry determined by function hop tests after anterior cruciate ligament rupture.
      ), less than 3 mm of increased anterior-posterior tibial displacement on Lachman or knee arthrometer testing, greater than 60% normalized knee separation distance on a video drop-jump test,
      • Noyes F.R.
      • Barber-Westin S.D.
      • Fleckenstein C.
      • Walsh C.
      • West J.
      The drop-jump screening test: Difference in lower limb control by gender and effect of neuromuscular training in female athletes.
      no effusion, full knee motion, normal patellar mobility, no or only slight patellar crepitus, and no pain or swelling with all activities. Other tests to consider are the single-leg squat test to determine postural and lower limb control as well as hip muscular function,
      • Ageberg E.
      • Bennell K.L.
      • Hunt M.A.
      • Simic M.
      • Roos E.M.
      • Creaby M.W.
      Validity and inter-rater reliability of medio-lateral knee motion observed during a single-limb mini squat.
      • Crossley K.M.
      • Zhang W.J.
      • Schache A.G.
      • Bryant A.
      • Cowan S.M.
      Performance on the single-leg squat task indicates hip abductor muscle function.
      the multistage fitness test to determine maximal oxygen uptake,
      • Ramsbottom R.
      • Brewer J.
      • Williams C.
      A progressive shuttle run test to estimate maximal oxygen uptake.
      and the 60-second sit-up test
      1985 National school population fitness survey from President's Council on Physical Fitness and Sports.
      or other core strength measures.
      • Okada T.
      • Huxel K.C.
      • Nesser T.W.
      Relationship between core stability, functional movement, and performance.
      If isokinetic test equipment is not available, a 1-repetition maximum bench press and leg press are recommended if weight room equipment is available, along with an experienced test administrator and a sufficient amount of time to safely conduct these tests.
      • Kraemer W.J.
      • Patton J.F.
      • Gordon S.E.
      • et al.
      Compatibility of high-intensity strength and endurance training on hormonal and skeletal muscle adaptations.
      • Reiman M.P.
      • Manske R.C.
      Functional testing in human performance.
      One limitation to this review is the potential that some of the investigations did in fact objectively measure certain indices before athletes were released to full sports activities but did not include this information in the article. Authors of future studies are encouraged to provide these important details. Although recommendations are made for tests and achievement of certain criteria, whether this detailed analysis will reduce the rate of injury to either knee after ACL reconstruction remains to be determined. We did not assess each study for its methodologic quality. However, because we were examining the methods used by investigators, and not outcomes, we did not believe such an assessment was required.

      Conclusions

      The published literature shows that a lack of consensus regarding the appropriate criteria for releasing patients to unrestricted sports activities exists after ACL reconstruction. A systematic review of the literature was conducted to identify the factors investigators have used over the last 10 years to determine when return to athletics is appropriate. Of 264 studies that met our study inclusion criteria, 105 (40%) failed to provide any measures for return to sports after surgery. Only 35 studies (13%) included objective criteria that consisted of the categories of muscle strength or thigh circumference, general knee examination, single-leg hop tests, Lachman rating, or validated questionnaires. Only 2 studies used 4 to 5 measurable factors to determine whether release to unrestricted activities was appropriate. The results of this systematic review show noteworthy problems and a lack of objective assessment before release to athletics. Measurement of muscle strength, stability, neuromuscular control, and function is recommended before release to unrestricted activities.

      Supplementary data

      • Video

        ACL rehabilitation program information, along with recommendations for criteria required to enter patients into advanced neuromuscular retraining programs and final release to unrestricted sports activities.

      References

        • Baer G.S.
        • Harner C.D.
        Clinical outcomes of allograft versus autograft in anterior cruciate ligament reconstruction.
        Clin Sports Med. 2007; 26: 661-681
        • Hartigan E.H.
        • Axe M.J.
        • Snyder-Mackler L.
        Time line for noncopers to pass return-to-sports criteria after anterior cruciate ligament reconstruction.
        J Orthop Sports Phys Ther. 2010; 40: 141-154
        • Hiemstra L.A.
        • Webber S.
        • MacDonald P.B.
        • Kriellaars D.J.
        Contralateral limb strength deficits after anterior cruciate ligament reconstruction using a hamstring tendon graft.
        Clin Biomech (Bristol, Avon). 2007; 22: 543-550
        • Eitzen I.
        • Holm I.
        • Risberg M.A.
        Preoperative quadriceps strength is a significant predictor of knee function two years after anterior cruciate ligament reconstruction.
        Br J Sports Med. 2009; 43: 371-376
        • Madhavan S.
        • Shields R.K.
        Neuromuscular responses in individuals with anterior cruciate ligament repair.
        Clin Neurophysiol. 2011; 122: 997-1004
        • Orishimo K.F.
        • Kremenic I.J.
        • Mullaney M.J.
        • McHugh M.P.
        • Nicholas S.J.
        Adaptations in single-leg hop biomechanics following anterior cruciate ligament reconstruction.
        Knee Surg Sports Traumatol Arthrosc. 2010; 18: 1587-1593
        • Bonfim T.R.
        • Paccola C.A.
        • Barela J.A.
        Proprioceptive and behavior impairments in individuals with anterior cruciate ligament reconstructed knees.
        Arch Phys Med Rehabil. 2003; 84: 1217-1223
        • Deneweth J.M.
        • Bey M.J.
        • McLean S.G.
        • Lock T.R.
        • Kolowich P.A.
        • Tashman S.
        Tibiofemoral joint kinematics of the anterior cruciate ligament-reconstructed knee during a single-legged hop landing.
        Am J Sports Med. 2010; 38: 1820-1828
        • Gokeler A.
        • Hof A.L.
        • Arnold M.P.
        • Dijkstra P.U.
        • Postema K.
        • Otten E.
        Abnormal landing strategies after ACL reconstruction.
        Scand J Med Sci Sports. 2010; 20: e12-e19
        • Tashman S.
        • Kolowich P.
        • Collon D.
        • Anderson K.
        • Anderst W.
        Dynamic function of the ACL-reconstructed knee during running.
        Clin Orthop Relat Res. 2007; 454: 66-73
        • Papannagari R.
        • Gill T.J.
        • Defrate L.E.
        • Moses J.M.
        • Petruska A.J.
        • Li G.
        In vivo kinematics of the knee after anterior cruciate ligament reconstruction: A clinical and functional evaluation.
        Am J Sports Med. 2006; 34: 2006-2012
        • Gao B.
        • Zheng N.N.
        Alterations in three-dimensional joint kinematics of anterior cruciate ligament-deficient and -reconstructed knees during walking.
        Clin Biomech (Bristol, Avon). 2010; 25: 222-229
        • Hui C.
        • Salmon L.J.
        • Kok A.
        • Maeno S.
        • Linklater J.
        • Pinczewski L.A.
        Fifteen-year outcome of endoscopic anterior cruciate ligament reconstruction with patellar tendon autograft for “isolated” anterior cruciate ligament tear.
        Am J Sports Med. 2011; 39: 89-98
        • Pinczewski L.A.
        • Lyman J.
        • Salmon L.J.
        • Russell V.J.
        • Roe J.
        • Linklater J.
        A 10-year comparison of anterior cruciate ligament reconstructions with hamstring tendon and patellar tendon autograft: A controlled, prospective trial.
        Am J Sports Med. 2007; 35: 564-574
        • Salmon L.J.
        • Russell V.J.
        • Refshauge K.
        • et al.
        Long-term outcome of endoscopic anterior cruciate ligament reconstruction with patellar tendon autograft: Minimum 13-year review.
        Am J Sports Med. 2006; 34: 721-732
        • Paterno M.V.
        • Schmitt L.C.
        • Ford K.R.
        • et al.
        Biomechanical measures during landing and postural stability predict second anterior cruciate ligament injury after anterior cruciate ligament reconstruction and return to sport.
        Am J Sports Med. 2010; 38: 1968-1978
        • Mascarenhas R.
        • Tranovich M.
        • Karpie J.C.
        • Irrgang J.J.
        • Fu F.H.
        • Harner C.D.
        Patellar tendon anterior cruciate ligament reconstruction in the high-demand patient: Evaluation of autograft versus allograft reconstruction.
        Arthroscopy. 2010; 26: S58-S66
        • Neeter C.
        • Gustavsson A.
        • Thomeé P.
        • Augustsson J.
        • Thomeé R.
        • Karlsson J.
        Development of a strength test battery for evaluating leg muscle power after anterior cruciate ligament injury and reconstruction.
        Knee Surg Sports Traumatol Arthrosc. 2006; 14: 571-580
        • Kvist J.
        Rehabilitation following anterior cruciate ligament injury: Current recommendations for sports participation.
        Sports Med. 2004; 34: 269-280
        • van Grinsven S.
        • van Cingel R.E.
        • Holla C.J.
        • van Loon C.J.
        Evidence-based rehabilitation following anterior cruciate ligament reconstruction.
        Knee Surg Sports Traumatol Arthrosc. 2010; 18: 1128-1144
        • Borchers J.R.
        • Pedroza A.
        • Kaeding C.
        Activity level and graft type as risk factors for anterior cruciate ligament graft failure: A case-control study.
        Am J Sports Med. 2009; 37: 2362-2367
        • Hui C.
        • Salmon L.J.
        • Kok A.
        • et al.
        Long-term survival of high tibial osteotomy for medial compartment osteoarthritis of the knee.
        Am J Sports Med. 2011; 39: 64-70
        • Shelbourne K.D.
        • Gray T.
        • Haro M.
        Incidence of subsequent injury to either knee within 5 years after anterior cruciate ligament reconstruction with patellar tendon autograft.
        Am J Sports Med. 2009; 37: 246-251
        • Myklebust G.
        • Holm I.
        • Maehlum S.
        • Engebretsen L.
        • Bahr R.
        Clinical, functional, and radiologic outcome in team handball players 6 to 11 years after anterior cruciate ligament injury: A follow-up study.
        Am J Sports Med. 2003; 31: 981-989
        • Risberg M.A.
        • Holm I.
        The long-term effect of 2 postoperative rehabilitation programs after anterior cruciate ligament reconstruction: A randomized controlled clinical trial with 2 years of follow-up.
        Am J Sports Med. 2009; 37: 1958-1966
        • Marchant B.G.
        • Noyes F.R.
        • Barber-Westin S.D.
        • Fleckenstein C.
        Prevalence of nonanatomical graft placement in a series of failed anterior cruciate ligament reconstructions.
        Am J Sports Med. 2010; 38: 1987-1996
        • Risberg M.A.
        • Holm I.
        • Myklebust G.
        • Engebretsen L.
        Neuromuscular training versus strength training during first 6 months after anterior cruciate ligament reconstruction: A randomized clinical trial.
        Phys Ther. 2007; 87: 737-750
        • Noyes F.R.
        • Barber S.D.
        • Mangine R.E.
        Abnormal lower limb symmetry determined by function hop tests after anterior cruciate ligament rupture.
        Am J Sports Med. 1991; 19: 513-518
        • Noyes F.R.
        • Barber-Westin S.D.
        • Fleckenstein C.
        • Walsh C.
        • West J.
        The drop-jump screening test: Difference in lower limb control by gender and effect of neuromuscular training in female athletes.
        Am J Sports Med. 2005; 33: 197-207
        • Ageberg E.
        • Bennell K.L.
        • Hunt M.A.
        • Simic M.
        • Roos E.M.
        • Creaby M.W.
        Validity and inter-rater reliability of medio-lateral knee motion observed during a single-limb mini squat.
        BMC Musculoskelet Disord. 2010; 11: 265
        • Crossley K.M.
        • Zhang W.J.
        • Schache A.G.
        • Bryant A.
        • Cowan S.M.
        Performance on the single-leg squat task indicates hip abductor muscle function.
        Am J Sports Med. 2011; 39: 866-873
        • Ramsbottom R.
        • Brewer J.
        • Williams C.
        A progressive shuttle run test to estimate maximal oxygen uptake.
        Br J Sports Med. 1988; 22: 141-144
      1. 1985 National school population fitness survey from President's Council on Physical Fitness and Sports.
        US Department of Health and Human Services PHS, Office of the Assistant Secretary for Health, Washington, DC1986
        • Okada T.
        • Huxel K.C.
        • Nesser T.W.
        Relationship between core stability, functional movement, and performance.
        J Strength Cond Res. 2011; 25: 252-261
        • Kraemer W.J.
        • Patton J.F.
        • Gordon S.E.
        • et al.
        Compatibility of high-intensity strength and endurance training on hormonal and skeletal muscle adaptations.
        J Appl Physiol. 1995; 78: 976-989
        • Reiman M.P.
        • Manske R.C.
        Functional testing in human performance.
        Champaign (IL): Human Kinetics. 2009;
        • Nakata K.
        • Shino K.
        • Horibe S.
        • et al.
        Arthroscopic anterior cruciate ligament reconstruction using fresh-frozen bone plug-free allogeneic tendons: 10-year follow-up.
        Arthroscopy. 2008; 24: 285-291
        • Keays S.L.
        • Bullock-Saxton J.E.
        • Keays A.C.
        • Newcombe P.A.
        • Bullock M.I.
        A 6-year follow-up of the effect of graft site on strength, stability, range of motion, function, and joint degeneration after anterior cruciate ligament reconstruction: Patellar tendon versus semitendinosus and gracilis tendon graft.
        Am J Sports Med. 2007; 35: 729-739
        • Drogset J.O.
        • Grøntvedt T.
        • Robak O.R.
        • Mølster A.
        • Viset A.T.
        • Engebretsen L.
        A sixteen-year follow-up of three operative techniques for the treatment of acute ruptures of the anterior cruciate ligament.
        J Bone Joint Surg Am. 2006; 88: 944-952
        • Ait Si Selmi T.
        • Fithian D.
        • Neyret P.
        The evolution of osteoarthritis in 103 patients with acl reconstruction at 17 years follow-up.
        Knee. 2006; 13: 353-358
        • Hertel P.
        • Behrend H.
        • Cierpinski T.
        • Musahl V.
        • Widjaja G.
        ACL reconstruction using bone-patellar tendon-bone press-fit fixation: 10-year clinical results.
        Knee Surg Sports Traumatol Arthrosc. 2005; 13: 248-255