A knee brace for assisting the extension or flexing of a limb comprises substantially rigid upper and lower frames connected by a hinge, the upper frame being secured to the leg by an upper strap. A stabilizing strap for fixing the lower frame to the user's leg comprises an inelastic band, cord or other flexible securing member for circumscribing the user's leg having a fastening element for fixing the securing member in a set position. The securing member is affixed to the arms of the lower frame, slidably extending through at least one strap support provided by at least one of the arms of the lower frame. When the brace is in position on a user's leg the stabilizing strap is able to move through at least one strap support in a generally horizontal direction while supporting the lower frame in the vertical direction.
