Kinematic analysis of one-leg long hopping in patients with an old rupture of the anterior cruciate ligament.

Sixteen males (mean age 30 ± 8 years), all possessing an old rupture of the anterior cruciate ligament which had not been repaired surgically, underwent a biomechanical evaluation of a one-leg long hop using opto-electronic motion analysis and ground reaction force analysis. In concordance with previous findings, the length of a one-leg long hop on the injured leg was shorter than on the non-injured leg. Furthermore, performance of the non-injured leg was impaired compared to a reference group. There was no significant difference in knee flexion angles at impact, but there was a lower eccentric knee angular velocity in the injured leg, 597°/s (SD 101), as compared with 701°/s (SD 130) for the non-injured leg (P < 0·01). No statistically significant differences were found for the reaction force components. The level of evaluation, mechanisms for the provocation of knee joint instability and possible adaptations are discussed.