The preceding discussion has profiled the three different types of knee braces which are available on today's market. It also has attempted to discuss the controversies surrounding these braces and to analyze the scientific data presented to date. Prophylactic braces have been shown to be ineffective in preventing knee injuries in its present day design. Evidence also has shown that their use may even lead to increased knee injuries. Rehabilitative braces, on the other hand, do serve a useful purpose in regard to the operative and non-operative treatment of ligamentous knee injuries. With their ease of application and control of joint motion, they are an important addition to the surgeon's armamentarium. One must keep in mind, however, that these braces provide little static anterior/posterior control and the hinge settings may not actually affect true joint motion. Functional knee braces may play a role in the treatment of patients with pathological laxity due to an injury of the anterior cruciate ligament. Combined with an adequate rehabilitation program and activity modification, these braces do limit excessive anterior tibial translation under low loading conditions. However, under conditions of high loading these braces provide little or no resistance to anterior translation. Therefore, in most sporting activities, their efficacy is questionable. Knee bracing continues to be a complex and controversial topic in the field of orthopedic surgery.(ABSTRACT TRUNCATED AT 250 WORDS)