Decrease in valgus stiffness after medial knee ligament injury. A 4-year clinical and mechanical follow-up study in 38 patients.

The clinical outcome after partial rupture of the medial collateral knee ligament is reported to be good, but there is a lack of objective assessment of persistent valgus laxity. We prospectively followed 38 consecutive patients with an isolated partial medial ligament rupture. After diagnostic arthroscopy, all patients were treated by early functional rehabilitation. At 4 years, besides clinical routine laxity tests, varus/valgus rotation, internal/external tibial rotation, initial and endpoint valgus stiffnesses, initial and endpoint internal/external rotational stiffnesses were measured by instrumented computerized passive motion analysis (Genucom). Most patients had normal knee function and muscle strength as early as 3 months after injury and returned to their pre-injury activity level without problems. At 4 years, 2 knees had minor residual valgus laxity at the manual examination, all other knees appeared stable. The instrumented tests also showed equal varus/valgus rotations and internal/external rotational stiffnesses in injured and healthy knees, but a decrease in the initial valgus stiffness and a decrease in the internal/external tibial rotation of the injured knee.