Recommended by orthopedic surgeons, rheumatologists, physical therapists and physicians this specially designed knee strap helps alleviate pain. It applies pressure upon the patellar tendon below the kneecap to stabilize the kneecap and reduce displacement. It provides many people with increased mobility and a marked reduction in the pain and discomfort caused by arthritis, knee degeneration, runners knee, and various knee disorders. Polyester. Can be worn on either knee. Choose: (Measure circumference below kneecap) S(10"-12½"), M(12½"-14½"), L(14½"-16 ½"), or XL(16½"-18").