Whether you are watching a high school basketball game, a professional soccer match, or weekend warriors on the ski slopes, chances are you will see someone wearing an anterior cruciate ligament (ACL) functional brace. However, it is just as likely that there are other ACL-injured athletes on the court or field who do not wear braces. Under what circumstances is it appropriate for an athlete to wear a brace? Does brace prescription follow some protocol based on the outcome of a patient's injury and rehabilitation, or does it depend simply on whether he or she is willing and able to purchase one?

While other aspects of ACL rehabilitation seem to follow a generally agreed-on protocol, guidelines for brace prescription are not as clear. Perhaps this is because investigations into the efficacy of functional braces have produced inconsistent, if not unfavorable, results.

The role of a functional ACL brace is to stabilize the knee joint by minimizing anterior/posterior (AP) translation and/or rotation of the tibiofemoral joint surfaces. Numerous studies over the years have attempted to determine whether various braces actually accomplish this goal.

In ACL-deficient knees, functional braces have been shown to decrease anterior translation of the tibia up to 40% passively, or up to 85% with simultaneous cocontraction of the quadriceps, hamstrings, and calf musculature. The ability of a brace to lessen such translation in an ACL-reconstructed joint is questionable, however. And theoretically, a successful ACL graft with strong fixation should not need a brace for further stabilization during daily functioning and controlled athletic activities.¹

Studies have also assessed athletic performance while using a functional brace. Dynamic testing showed decreased torque and velocity of contraction in the quadriceps with brace use.^2,3 The reason for this is uncertain, but may be due to a decreased need for muscular control (because of the mechanical stabilization of the brace), or to a direct inhibition of the muscles from the pressure exerted by the straps of the brace.⁴

Functional testing during athletic activities has shown decreased running speed and turning time^2,5 and an increase in overall energy expenditure^2,3, likely due to the weight of the brace, friction of the hinges, and/or tightness or slipping of the brace. Furthermore, functional braces have been shown to have no significant effect on measured proprioception.^2,3,5

Functional braces may provide actual mechanical stability to ACL-deficient knees, but in a successfully reconstructed knee, the braces do not seem to perform as intended. In fact, they may actually hamper performance. In many cases, the brace may serve only to boost confidence and possibly prevent further injury.⁶

While these findings are meaningful to us as clinicians, they are les important to a patient whose main concern is his/her successful return to athletic activities. Despite the lack of substantial scientific evidence that functional braces are biomechanically effective, the fact remains that many patients believe a brace is helpful in returning them to sports and boosting confidence. These intangibles are important considerations in deciding whether a brace is indicated.

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