Figure 10. Closed-Kinetic-Chain Yielding/Holding Isometric Load-Progression.

The closed-kinetic-chain (CKC) yielding/holding isometric load progression should start with the double-leg squat exercise in low levels of knee flexion (a, non-surgical limb posted). Exercise selection can be advanced to include the split-squat exercise (b), and a heel wedge can be utilized to increase external knee flexion moment/load on the quadriceps (c). Submaximal yielding/holding isometric contractions should be advanced onto maximal effort contractions through increasing the degree of knee flexion/external knee flexion moment (d) or the progression of external load. Maximal effort CKC machine or weightbearing exercises with upper body stabilization (c, d) are preferred to free-weight or compound exercises prescribed without external support. Asterisk, use of wall support to stabilize the body during exercise (c, d); black lines, approximate tibial and femoral bone markers; red arrows; approximate ground reaction force-vector; white arrows, progression of knee/quadriceps load through the advancement of exercise position (a-c); white circle; estimated center of joint rotation; yellow arrow, progression of knee/quadriceps load by advancing the degree of knee flexion/external knee flexion moment (d); yellow shading; depiction of knee/quadriceps-dominant loading with increasing external knee flexion moment (a-d).