Biomechanical function of the posterior horn of the medial meniscus: a human cadaveric study.

Partial and total meniscectomies have been known to develop a high rate of osteoarthritis, but not in quantitative terms. In this study, we investigated the role of the posterior horn of the medial meniscus (PMM) by measuring the changes in the multiple degrees of freedom knee kinematics. Using a robotic/universal force-moment testing system, the 5-degree-of-freedom kinematics at selected flexion angles of human cadaveric knees (age, 35-72 years) in response to a 10 N.m varus torque were measured. Ten knees were studied with the knee at full extension and at 30 degrees, 60 degrees, and 90 degrees of flexion. Each knee was tested in a series of four conditions: intact, with one-third of PMM resected, with two-thirds PMM resected, and finally with the entire PMM resected. Anterior tibial translation increased significantly by 1.4 mm and 4.1 mm at 30 degrees of knee flexion when the two-thirds and entire PMM were resected, respectively. Similarly, external tibial rotation significantly increased 2.2 degrees and 6.7 degrees at 30 degrees of knee flexion with the two-thirds and entire PMM resected, respectively. These results suggest that resecting more than two-thirds of the PMM will have a significant effect on the kinematics of the knee.