Knee orthosis and joint construction therefor

An orthotic knee joint assembly comprising a rigid planar femoral member having a head portion with a narrow arcuate polycentric bearing surface and having an arm portion projecting from said head portion and adapted to extend upwardly alongside a wearer's upper leg;

• a rigid tibial member having a body portion and an arm portion adapted to extend downwardly alongside a wearer's lower leg;
• said body portion having a pair of planar side walls spaced apart to define a narrow open-topped recess receiving said head portion and having an arcuate camming surface engaging said bearing surface for guiding movement of said members between extension and flexion along constantly changing instantaneous axes of rotation, said bearing surface being slidable posteriorly and anteriorly along said camming surface when said members are in flexion and being generally congruent with said camming surface when said members are in extension;
• said head portion also having its planar surfaces in slidable engagement with the opposing surfaces of said side walls of said body portion within said recess;
• a rigid anchor plate extending alongside one of said side walls and having a connecting portion secured to said arm portion of said femoral member;
• and a plurality of flexible non-stretchable guide straps having lower ends secured to said tibial member at at least one connecting point and having upper ends secured to said anchor plate at a plurality of connecting points;
• said straps being mounted for sequential tensioning and untensioning as said members are moved between extension and flexion to exert forces similar to those that would be exerted by a selected normal knee ligament during external loading while avoiding the exertion of forces not associated with such ligament that might constrain knee joint articulation.

A knee orthosis comprising a pair of hinge assemblies adapted to be disposed on opposite sides of a wearer's knee, each hinge assembly including an upper arm portion adapted to extend upwardly alongside the wearer's upper leg and a lower arm portion adapted to extend downwardly alongside the wearer's lower leg;

• said hinge assemblies having constantly changing instantaneous axes of rotation as said upper and lower arm portions are moved between extension and flexion;
• means for securing said upper arm portions along opposite sides of a wearer's upper leg, said means including a first interfacial member connected to said upper arm portions and shaped to extend anteriorly across the upper leg of a wearer, and strap means for detachably securing said first interfacial member against the upper leg;
• and means for securing said lower arm portions along opposite sides of a wearer's lower leg, said second-mentioned means including a second interfacial member connected to said lower arm portions and shaped to extend anteriorly across the lower leg of a wearer, strap means for detachably securing said second interfacial member against the lower leg, and a third interfacial member adapted to engage the lower leg at a point spaced above said second interfacial member and directly below a wearer's knee, said third interfacial member being equipped with strap means engaging said lower arm portions and adapted to extend about the upper portion of a wearer's lower leg to prevent tibial drawer.