Functional analysis of untreated and reconstructed posterior cruciate ligament injuries.

Twenty patients with old ruptures of the PCL were analyzed. Ten patients were untreated, and ten patients had reconstruction of the PCL with the medial head of the gastrocnemius. The patients' gait was analyzed using high speed photography, footswitches, electromyography, and force plate. Patients were studied while walking, running, and stair-climbing. A Cybex muscle strength evaluation was also performed. Clinically, all patients had moderate to severe posterior instability. Five of the 20 patients also had posterolateral instability. Cybex testing showed quadriceps deficits in both reconstructed and untreated groups when comparing involved and uninvolved limbs. The reconstructed group also had deficits on hamstring Cybex testing. Footswitch data showed only minimal abnormalities. Gait velocity of walking was 91% of normal with a normal cadence. There was no significant difference in the single limb support times between the involved and uninvolved limbs in walking, fast walking, or running. The photometric data showed a tendency for increased knee flexion during the midstance phase of the gait cycle in comparing involved and uninvolved limbs. The knee flexion angles during midstance were similar in the patients with posterior instability when compared to the patients with the additional posterolateral instability. Force plate data showed decreased foot-floor reaction in the untreated group during terminal stance while walking. Similar findings were found in the reconstructed group during running.(ABSTRACT TRUNCATED AT 250 WORDS)