Most functional movements in the lower extremity take place when the foot is on the ground. The hip, knee and ankle joints, together, comprise the lower extremity kinetic chain. Muscle contractions in closed kinetic chain motion are different from open kinetic chain motion. Joint motion is caused by many controlled muscle contractions. Closed kinetic chain rehabilitation is more closely related to function than open kinetic chain exercise.
Closed kinetic chain exercises are safer for the healing anterior cruciate ligament (ACL) graft. Research has shown that ACL strain is reduced during closed kinetic chain exercise. Through recruitment of all hip, knee and ankle muscles in synergy, specific training and strengthening are functional and effective.
Research has also shown that closed kinetic chain exercise is more effective in patellofemoral dysfunction, improving reflex stabilization and proprioception, reducing pain and promoting a return to normal daily activities and sports. For athletes, closed kinetic chain exercise improves strength and jumping ability more than open kinetic chain exercise.
While open kinetic chain exercise certainly has its benefits and its own place in rehabilitation and strength training of the lower extremities, it is important to incorporate (and quite possibly emphasize) closed kinetic chain exercises for the greatest functional gains.