82 patients, 40-80 years of age, with knee osteoarthritis were randomized to treatment with either hyaluronic acid injections or a physical therapy program. Patients allocated to hyaluronic acid injections were administered either high-molecular-weight HA (Hylan G-F20) or low-molecular-weight HA (Orthovisc). Results demonstrated significant within-group improvement with Hylan G-F20 for pain and function over 12 months, significant within-group improvement with Orthovisc for pain, alone, over 12 months, and significant within-group improvement with physical therapy for pain and function up to 9 months.