This is called a patellar mobilization — gentle movement of the kneecap performed by a physical therapist or taught for home use after total knee replacement surgery. . After knee replacement, the kneecap sits on top of the new joint and needs to glide smoothly as the knee bends and straightens. Swelling, stiffness, and protective muscle guarding can cause the patella to become restricted, which can limit motion and increase discomfort. . Patellar mobilizations help by improving kneecap mobility