a biomechanical study of lateral release and elmslie-trillat procedures to restabilisethe maltracktng patella

the resistant* of patesa against lateral displacement (le. the stability), was studied tinder a range of conditions in vitro, at a range of knee flexion angles. muscle forces were applied in physiological directions along the separate quadriceps muscles. normal muscle actions with constant tension showed constant patellar stability up to sixty degrees knee flexion, and then a significant increase at ninety degrees. a pathological knee was simulated by relaxing vastus medians, and ■ lateral stability then dropped by 47%. isolated rttlnaeular release in the pathological knee did not improve stability significantly towards normal, while 6mm tibial tubercle medlaesatum restored stabtbty by 52% towards normal, except neat jum extension. combined release phis tubercle medtafisathm. restored stability 59% towards normal in knee flexion, and 23% up to ten degrees flexion.