Knee joint orthosis

Claim 1

A knee-joint orthosis for persons whose legs are weak or unstable, comprising: a first elongate member adapted to be secured along the lower leg below the knee, a second elongate member adapted to be secured along the upper leg above the knee, the two elongate members being hinged together at a pivot location which, when the elongate members are secured to the leg, can be substantially aligned with the hypothetical pivot axis between the upper and lower leg, and a tension member secured between a first location which moves with said first member and a second location which moves with said second member, the force of the tension member acting along a line which is spaced from the pivot location and which is such that tension in said tension member increases as the leg is flexed, whereby the moment acting to extend the leg increases as the leg is flexed, the second location being on a cog member pivoted about said pivot location, said second location being spaced from said pivot location, the second elongate member including means for rotating the cog member along with the second elongate member about said pivot location, said means including a dog pivoted to the second elongate member, the dog being pivotally mounted to move between (a) a first position in which it bears against said cog member and rotates the same along with the second elongate member, and (b) a second position in which it frees the cog member for movement independent of said second elongate member.