Dynamic Lateral Patellar Tilt in the Anterior Cruciate Ligament-Deficient Knee

Abstract

An open-configuration magnetic resonance imaging scanner was used to document patellar tracking abnormalities in 11 anterior cruciate ligament-injured knees. The contralateral normal knees were used as controls. Images were obtained with the quadriceps muscles at rest (knee flexion at 40°, 25°, and 10°) and with the quadriceps muscles contracted (knee flexion at 40° and 25°). When the quadriceps muscles were at rest there were no differences in patellar alignment between the anterior cruciate ligament-injured knees and the contralateral normal knees. When the quadriceps muscles were maximally contracted at 40° of flexion, the patellae of the anterior cruciate ligament-injured knees tilted laterally 3.6° relative to the resting state. When the quadriceps muscles were contracted at 25° of flexion, the patellae of the anterior cruciate ligament-injured knees tilted laterally approximately 4° relative to the resting state. Quadriceps-active lateral patellar tilt at 25° of flexion was greater in the anterior cruciate ligament-injured knees than in the contralateral normal knees, and it correlated with instrumented measurements of anterior tibial translation. Dynamic lateral patellar tilt during open kinetic chain exercises and during other activities that produce anterior tibial translation may contribute to extensor mechanism dysfunction in the anterior cruciate ligament-injured knee.