USE OF KNEE BRACES IN SPORT - CURRENT RECOMMENDATIONS

This article provides a review of the progress that has been made on t he biomechanical, functional performance and epidemiological investiga tions into the effectiveness of prophylactic knee braces (PKBs) since the position statement against their use was issued in 1987 by the Ame rican Academy of Orthopaedics and a review of this subject was last pu blished in Sports Medicine in 1989 by Montgomery and Korziris. The evo lution of the salient design features of three surrogate knee models a re reviewed along with the results of PKB effectiveness and safety fac tor testing. While still too limited in scope to be totally realistic, major advances have been made in the sophistication of the present bi omechanics laboratory testing conditions. The on-the-field functional performance effects of wearing a knee brace are not always manifest in all individuals. The efficacy of PKBs remains in question but recent studies have taught us enough to put their use into perspective. While they may play some role, PKBs probably represent the least important factor in influencing the likelihood that a medial collateral ligament (MCL) sprain will occur. On the other hand, there is no evidence that such braces put added valgus pressure on some knees, or that wearing a brace is associated with an increased frequency or severity of knee or ankle injury. All else being equal, from the biomechanical studies, we know that whilst some braces are better than others, currently ava ilable PKBs can provide 20 to 30% greater resistance to a lateral blow , with the possibility that the anterior cruciate ligament (ACL) is gi ven even greater protection than the MCL. This appears to be true when the lateral blow is of sufficient magnitude to cause significant medi al joint line opening, but is not as great at the very lowest levels o f impact. Regardless of the material they are made of, the most effect ive PKBs are those sufficiently stiff to prevent an external blow at t he joint line from causing brace hinge contact with the knee tissues. Based on the superior results of the custom-fit functional braces, the most important future design feature appears to be the sizing and fit ting of the thigh and tibial cuffs. On the negative side, the presence of a brace may slow an athlete's straight-ahead sprint speed and caus e early fatigue to its wearer. This effect appears to vary from one br ace to another according to its weight, design features, and pressure from the leg and thigh straps. However, it appears that knee braces do have the potential to restrict performance of the athlete for high-sp eed running but the effect is related to several factors. The weight o f the brace resultant friction of the hinges, completeness of fit, and tightness of straps appear to be important. The most measurable effec ts include: increased muscular relaxation pressures; increased energy expenditure; and a related increase in blood lactate levels, maximal t orque output, oxygen consumption and heart rate. On the other hand, ex perienced brace wearers and larger, stronger individuals displayed few er, or no effects of donning a brace. Improvements in the protectivene ss of the PKB are likely to accompany improvements in the ability to c ontour the braces to fit each individual's leg in the equipment room w ithout the added expense of the cast-moulding process. Further improve ment may be realised by friction-free polycentric joints, as well as a n attachment system that minimises thigh and calf soft tissue compress ion perhaps by incorporating the braces into the trousers of the unifo rm to provide suspension from the waist.