THE EFFECT OF INTERSEGMENTAL KNEE MOMENTS ON PATELLOFEMORAL CONTACT MECHANICS IN CYCLING

The aim of this study was to evaluate the effect of bicycle pedal desi gn on the mechanics of the patellofemoral joint. Previous research det ermined that for certain riders the non-driving varus and internal kne e moments could be reduced by switching from fixed to free floating pe dals (Ruby and Hull, 1993). It was postulated that the presence of var us and internal knee moments during fixed pedal cycling may adversely affect patellofemoral joint contact mechanics which could lead to the development of anterior knee pain. To investigate the effect of pedal design the hypothesis that varus and internal intersegmental knee mome nts significantly increase patellofemoral contact pressure, contact ar ea and contact force was tested. To test this hypothesis cycling loads were simulated in vitro using a six-degree-of-freedom load applicatio n system (LAS). Using the LAS, varus moments ranging from 0-20 Nm and internal knee moments ranging from 0-10 Nm were applied simultaneously with quadriceps force at knee flexion angles of 60 and 90 degrees. Pa tellofemoral contact patterns were measured using pressure sensitive f ilm. An applied 10 Nm internal moment significantly increased both con tact area by 16% and contact force by 22% at 90 degrees of flexion. Th e application of a 20 Nm varus moment modestly yet significantly incre ased contact area by 6% and contact force by 5%. When applied in combi nation, varus and internal knee moments increased contact area and for ce by as much as 29% and 28% respectively. The mean contact pressure w as not significantly increased by either of the two moments. The resul ts suggest that non-driving intersegmental knee moments subject the pa tellofemoral joint to loads and contact patterns which may accelerate the development of chondromalacia. (C) 1998 Elsevier Science Ltd. All rights reserved.