Abstract: A leg support apparatus is comprised of a pair of upper frames and a pair of lower frames pivotally connected at respective pivot joints. The upper frames are connected to a circumferentially adjustable cuff, which is adapted to be wrapped around the thigh of a user. The lower frames are attachable to the user's footwear. When the apparatus is being worn by the user, the upper frames are positioned on laterally opposed sides of the user's thigh and the lower frames are positioned on laterally opposed sides of the user's calf. When the user is in a sitting position with his leg flexed, the pivot joints are anteriorly positioned with respect to his knee joint. When the user extends his leg and puts weight on his footwear, the pivot joints are moved posteriorly, which moves the upper frames upwardly toward the cuff and tightens the cuff around the thigh to prevent the cuff from slipping.