THE EFFECT OF FUNCTIONAL BRACE WEAR AND HAMSTRING CONTRACTION ON THE ACL DEFICIENT KNEE 219

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Relatively low to moderate anterior loads can cause a large amount of anterior tibial translation in ACL deficient patients leading to subluxations and further joint damage. The purpose of this study was to evaluate the effects of a functional knee brace and hamstring contraction on the laxity/stiffness profile of the knee joint in ACL deficient subjects. Nine ACL deficient subjects underwent static and dynamic laxity testing of the knee joint with and without a functional brace (CTi Edge, Innovation Sports). Three trials of an instrumented Lachman (OSI CA-4000) exam were performed on the ACL deficient and non-injured knees with and without the brace using 45, 90, 135, and 180N of force. The subjects were also tested with the same protocol while contracting their hamstrings at 50% of maximum. Mean anterior tibial translation (ATT) without the brace was 12.4mm at 90N and 17.3mm at 180N. Translation decreased to 7mm and 12.8mm with the brace (p<0.05). Contraction of the hamstrings decreased ATT to 1.6mm at 90N and 3.3mm at 180N, an improvement of 89% (p<0.05) versus the no brace condition. The combination of hamstring contraction with bracing resulted in mean ATT of 2.0mm at 90N and 3.4mm at 180N and were not significant when compared to bracing alone. Dynamic testing produced no significant differences between brace conditions. At 45N, stiffness increased by 51% (6.8N/mm to 13.9N/mm) during brace wear (p<0.05). Larger anterior forces were required to produce an equivalent amount of translation in a braced, ACL deficient knee when compared to an unbraced ACL deficient knee. These results suggest that bracing may help prevent further damage to an ACL deficient knee by restricting excessive movement.