The treatment of osteoarthritis has typically focused on pain management and maintenance of articular function. Hyaluronic acid plays an important role in the structure and function of the articular matrix. Joints involved with osteoarthritis show a loss of hyaluronic acid. Intra-articular viscosupplementation of hyaluronic acid may restore the appropriate hyaluronic acid concentration in the matrix, improving function and decreasing pain. Petrella and associates studied the efficacy of intra-articular hyaluronic acid injections in resolving osteoarthritic joint pain and function loss compared with oral nonsteroidal anti-inflammatory drugs (NSAIDs).
In a double-blind trial, 120 patients with knee osteoarthritis were randomized into one of four treatment groups. Group 1 received 2 mL of hyaluronate sodium at a concentration of 10 mg per mL and an oral placebo (100 mg of lactose); group 2 received NSAIDs (75 mg of diclofenac and 200 mcg of misoprostol) and hyaluronate sodium; group 3 received NSAIDs and placebo (2 mL of isotonic saline); and group 4 received intra-articular and oral placebos. The intra-articular injections were administered once weekly over three weeks while NSAIDs or lactose were administered twice daily over 12 weeks. All subjects were given instructions for performing a 10-minute resistance exercise program at home on at least three days of each week. Subjects were also given acetaminophen as a rescue medicine to use as needed.
Self-reported pain reduction using the Western Ontario McMaster Universities Index (WOMAC) global measure of pain, stiffness, and disability was the primary outcome. Groups 1 and 3 showed significant improvement in the WOMAC global assessment of physical disability and the visual analog scale (VAS) for resting pain at week 4, while groups 1 and 2 showed further significant improvement from weeks 4 to 12. Groups 1 and 2 reported significantly less pain following self-paced walking and stepping, and group 1 demonstrated significantly faster self-paced walking and stepping at weeks 4 and 12. Using functional performance testing, maximum oxygen uptake was significantly higher in groups 1 and 2 at week 4.
The authors conclude that either intra-articular hyaluronic acid, NSAIDs, or simple exercises can improve knee osteoarthritis, in terms of resting pain and functional performance. Therapy with hyaluronic acid may be more effective at decreasing activity-related pain and may improve functional status more than NSAIDs or exercise therapy alone.