BACKGROUND: Osteoarthritis affects 16 million people in the United States, and the prevalence of osteoarthritis of the knee is 6 out of 100 people older than 30 years.1 Mainstays of therapy include analgesics, nonsteroidal anti-inflammatory drugs, corticosteroid injections, and surgery. Varying data indicate that exercise reduces pain and improves function in patients with osteoarthritis of the knee; however, the optimal exercise regimen is yet to be determined.
POPULATION STUDIED: Study subjects included 83 adults with osteoarthritis of the knee from various military clinics in Texas who were referred for physical therapy. Osteoarthritis of the knee was defined as knee pain plus 1 of the following criteria: (1) aged 38 years or younger and bony enlargement; (2) aged 38 years or older, morning stiffness for longer than 30 minutes, and bony enlargement; (3) crepitus on active motion, morning stiffness for longer than 30 minutes, and bony enlargement; or (4) crepitus on active motion, morning stiffness for longer than 30 minutes, bony enlargement, and aged 38 years or older. Mean age in the treatment group was 60±11 years and 62±10 years in the placebo group. Thirty-four participants were men and 49 were women. Exclusion criteria included a surgical procedure to either lower extremity within the previous 6 months, physical impairment unrelated to the knee restricting the ability to perform the 6-minute walk test, a lack of minimal English skills, corticosteroid injection in the knee within 30 days, inability to attend the required number of visits, and new medical therapy for knee osteoarthritis. Baseline characteristics were homogeneous.
STUDY DESIGN AND VALIDITY: Using techniques to conceal allocation assignment, eligible patients were randomly assigned to 1 of 2 groups. The treatment group (n=42) underwent manual physical therapy (passive movement, muscle stretching and strengthening, and soft tissue mobilization) and supervised exercise (range of motion exercise, stretching, and stationary bicycling) 2 times a week for a total of 8 sessions. They also received therapy directed at the lower back, hip, and ankles as indicated. Treatment group participants also performed a home exercise program. Patients in the placebo group (n=41) received sham ultrasound therapy for the same number of sessions and were instructed to continue their normal activities. Neither group was aware of the treatment that the other group was receiving. All outcome measurements were obtained by an observer blinded to group assignment. Intention-to-treat analysis was used to determine group differences in the number of surgical interventions at 1 year.
OUTCOMES MEASURED: The primary outcomes measured were Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores and 6-minute walk distances, both of which were obtained at baseline, 4 weeks, 8 weeks, and 1 year. The numbers of participants in each group requiring corticosteroid injection or surgical intervention were also recorded.
RESULTS: Included for analysis were the 33 patients (79%) in the treatment group and 36 patients (88%) in the placebo group who completed all treatment and testing through 8 weeks. By 8 weeks, WOMAC scores had improved by 56% over baseline in the treatment group and 15% in the placebo group (P <.001; number needed to treat [NNT]=2.4). Six-minute walk times improved by 13% in the treatment group; there was minimal change in the placebo group (P=.001; NNT=8). Follow-up in the treatment group at 1 year compared with 8-week testing revealed 6-minute walk times essentially unchanged and WOMAC scores still well below baseline. At 1-year follow-up, 5% of treated participants and 20% of those in the placebo group had undergone a total knee arthroplasty (P=.04%; NNT=6.7), and 5% of treated participants and 15% of those in the placebo group had received corticosteroid injections into the knee.
This 4-week well-tolerated program of physical therapy and supervised exercise can decrease symptoms and increase function in individuals with osteoarthritis of the knee and should be recommended as first-line therapy in conjunction with standard analgesics. It also reduces the need for total knee arthroplasty and steroid injection for at least 1 year. Because of the high cost of surgery (approximately $7500 plus recovery at my institution), the lesser cost of the described physical therapy program ($120 x 8 sessions), and the low NNT (7), such a strategy is likely to be cost-effective.