THE QUANTITATIVE MEASUREMENT OF NORMAL PASSIVE MEDIAL AND LATERAL PATELLAR MOTION LIMITS

To quantify normal motion, medial and lateral passive patellar motion limits were measured in 67 high school athletes randomly selected from a group of 1340 athletes undergoing preseason physical examinations. Patellar displacement was measured at knee flexion angles of 0-degrees and 35-degrees, using both a Patella Pusher (a hand-held force gauge) and a manual technique, and the results were compared. Demographic da ta and physical examination of the deceleration mechanism (Q angle, va stus medialis obliquus dysplasia, patella alta and baja, and valgus an d varus alignment) were correlated with patellar motion limits. With t he knee in extension, passive displacement of the patella averaged 9.6 mm medially and 5.4 mm laterally. In flexion, medial displacement ave raged 9.4 mm and lateral displacement averaged 10.0 mm. No positive co rrelations were found between demographic data or deceleration mechani sm examination parameters and patellar motion limits, suggesting that motion produced by the displacement force was limited by ligamentous r estraints only. The clinical assessment of the passive limits of patel lar motion should include examination at knee flexion angles of 0-degr ees and 35-degrees. The manually produced displacement was found to be more reproducible than displacement by the Patella Pusher (P < 0.05).