A difference in leg length occurs only rarely after knee replacement, usually after straightening of a severe bowed leg, but occurs frequently, at least temporarily, after hip replacement. Before surgery, one leg is often shorter than the other—or feels shorter because the joint has deteriorated. Your orthopedic surgeon chooses an implant and plans surgery so that your legs will be equal in length after healing. After hip replacement, muscle weakness or spasm and swelling around the hip may temporarily cause an abnormal tilt to your pelvis and make you feel as though your legs are unequal in length. Stretching and strengthening exercises help restore your pelvis to its proper position. It may be several months before you can tell if the discrepancy is real and needs to be addressed with the use of a lift in the shoe. When the discrepancy is accompanied by pain, surgery can correct both problems.