Traditional exercise regimes for patients with cartilage damage and osteoarthritis of the knee have emphasized low load, repetitive motion through pain-free ranges performed in supported postures usually sitting or lying down. Typical programs would center in such exercises as include straight-leg raises, knee extensions simulating a kicking motion, and quadriceps isometrics. All of these are joint-specific maneuvers that isolate motion to a single, pre-determined plane of movement, avoiding significant weight-bearing across the involved joint. Exercise progression is achieved by increasing repetitions and adding external resistance in the form of weights, usually loaded at the ankle. Further progression of the rehabilitation program to more functional activities such as stair climbing, walking, running, or return to sport is frequently determined by lifting loads arbitrarily assigned to the activity in question. While traditional exercises can be joint-specific to muscles supporting a knee weakened by osteoarthritis and are the starting point for patients with significant pain in weight-bearing postures, these exercises are marginal in their carryover to resuming functional activities.