We studied nine patients with an isolated, unrepaired rupture of the anterior cruciate ligament to evaluate whether well-rehabilitated patients with an old rupture of the anterior cruciate ligament had adapted their patterns of motor control in situations that provoke knee instability and if the possible adaptation results in a measurable decrease of the deteriorating sagittal shear load. The study was performed by means of a movement analysis system with synchronized force plate and electromyographic recordings. A different movement and muscular-activation pattern was found for the injured leg compared to the noninjured when performing a one-legged jump for distance. An internal knee model was developed and implemented. In that way, a simultaneously decreased capsuloligamentous sagittal load at the landing moment was shown.