Isolated partial tear of the anterior cruciate ligament.

Isolated partial tear of the anterior cruciate ligament should be suspected in the patient with effusion, flexion contracture and poorly localized pain and tenderness following a knee injury. The diagnosis is difficult to make from physical findings or even arthrography. Arthroscopy is helpful in making the diagnosis and in ruling out associated meniscus lesions. A normal meniscus should not be removed if this seemingly trivial lesion is the only abnormal finding at arthrotomy. Surgical treatment is not necessary if the diagnosis can be made by other means. This injury responds well to immobilization in extension followed by rehabilitation.