抄録
We performed physical therapy for a patient with osteoarthritis of the right knee accompanied by decreased support of the right lower limb while walking down stairs. The patient experienced increased rotation of the right crus with rapid right knee joint flexion in the right stance phase while walking down stairs. This was accompanied by pain in the lateral side of the right patellofemoral joint and the medial side of the right knee joint. In healthy subjects, electromyography detects muscle activity in the right medial hamstrings and vastus; however, the same was not detected in this patient. Physical therapy evaluation suggested the presence of anteromedial rotatory instability of the right knee. In addition, shortening of the right lateral hamstrings and weakness in the right medial hamstrings were observed, suggesting excessive external rotation of the crus, which decreased the strength of the right medial vastus and subsequently caused rapid flexion of the right knee joint. We assumed that these events caused lateral deviation of the right patella. Moreover, compression of the lateral side of the patellofemoral joint and extension of the medial side of the right knee caused pain. The patient’s physical therapy regimen included stretching of the lateral hamstrings, which increased the range of motion during extension of the right knee joint. Muscle strengthening exercises were performed for the right medial hamstrings and medial vastus. After 2 months of treatment, the strength of the medial hamstrings and vastus increased while shortening of the lateral hamstrings decreased. Electromyography revealed muscle activity in the medial hamstrings and vastus, similar to that observed in healthy subjects. Excessive external rotation of the crus improved, and slow flexion of the knee joint was achieved without pain while walking down stairs. These findings suggest that the medial hamstrings are involved in the control of excessive lateral rotation of the crus accompanied by anteromedial rotatory instability of the knee. To control abnormal knee joint movement accompanied by excessive rotation of the crus, it is useful to concentrate on rotatory instability of the crus and improve corresponding muscle activity.
