Knee orthoses of various constructions are known and commercially available for protecting knee ligaments as they heal following injuries occuring during athletics or other activities, for bracing the knee where there is chronic instability because of permanent ligament deficiency, for preventing stressing of the knee by a heavy cast worn because of femoral or tibial fracture, or for protecting a wearer pending or in place of surgery for joint repair or replacement. Such orthoses generally represent attempts to provide stability while duplicating the complex actions of the normal knee during flexion and extension. Polycentric or plural-hinge joints have been developed to bring the flexing action of the orthoses into closer conformity with the natural action of the knee but, nevertheless, current devices all have the common disadvantage of constraining normal knee motion because they do not replicate normal knee action. As a result, such orthoses interfere with normal movement, create stresses and loss of stability, tend to slip after a limited period of wear because of constraining forces causing pistoning, and cause skin irritation, patient discomfort, and even pain where the brace bears against bony prominences. In brief, the failure of current orthoses to provide stability while conforming with natural knee movement has greatly reduced the effectiveness of such devices, impaired normal patient movement, and, in extreme cases, caused patient discomfort and/or injury.
Reference may be had to D. Shurr et al, The Iowa Knee Orthosis, Orthotics and Prosthetics, Vol. 32, pp. 20-24 (March 1978) for a discussion of current and prior knee orthoses. U.S. Pat. Nos. 3,902,482, 3,799,159, 4,139,002, and 3,817,244 also reveal the state of the art.