Cam Impingement of the Posterior Femoral Condyle in Medial Meniscal Tears

Before meniscal repair and bone decompression, the relative contact pressure under the posterior segment of the medial meniscus was highest on deep flexion of the knee joint. Both the contact pressure measured with the film sensor and the flexion angle of the knee joint recorded by a video camera were monitored in real time on the display of a computer and recorded simultaneously by use of I-Scan software.

After resection of redundant bone tissue at the most proximal portion of the medial femoral condyle and the most distal part of the femoral metaphysis, the relative contact pressure under the posterior segment of the medial meniscus remained low even on deep flexion of the knee joint.

A 20-year-old woman visited our hospital because of crepitation and pain on deep flexion of the left knee joint. She had had no problem with her knee joints until she began to work as a nurse at a nursery school, where she needed to bend her knee joints deeply very often. She felt slight crepitation in the knee joint on deep flexion after working as a nurse. On day, she had the sudden onset of symptoms on deep flexion of the knee joint during sports activity. There was a longitudinal tear confined to the tibial side of the posterior segment with instability at the site of the tear. The posterior segment popped out anteriorly only on deep flexion of the knee joint, and it popped back on extension of the knee joint from deep flexion.