Joints, such as the hip, knee, and shoulder, normally contain a small amount of joint fluid. The joint fluid helps provide nutrition for the cartilage covering the bones as well as lubrication between the bones during range of motion. Normal joint fluid contains a substance known as hyaluronic acid.
Studies have found that in patients with osteoarthritis (see hip osteoarthritis, knee osteoarthritis, or shoulder osteoarthritis), the amount of hyaluronic acid is diminished. This finding prompted researchers to attempt to treat the symptoms of osteoarthritis by replenishing the hyaluronic acid; this concept is the basis of viscosupplementation injections.
Viscosupplementation injections consist of hyaluronic acid-like fluids which are injected directly into the arthritic joint. Studies have shown that viscosupplementation injections provide significant pain relief in patients with mild to moderate osteoarthritis.
Although the precise mechanism of action is unclear, these injections seem to have anti-inflammatory and pain-relieving properties. In addition the viscosupplementation fluid is thought to act as both a lubricant and a shock-absorber.
Their beneficial effects may last for several months or longer. Currently these injections are approved by the FDA for use in patients with knee osteoarthritis, but research is being conducted in other joints, such as the hip, ankle, and shoulder.
Several different companies make viscosupplementation products, such as Orthovisc and Hyalgan. Depending on the particular product used, the injections are given either as a single shot, or a series of shots (ranging from 3-5) given one time per week.
It is important to realize that unlike steroid injections, viscosupplementation injections do not provide immediate relief. The beneficial effects may not become apparent for several weeks. For the first 1-2 days after the injection, you should avoid excessive activity, such as prolonged standing or walking, heavy lifting, or jogging.
What you Need to know about Hyaluronic Acid Injections
Knee osteoarthritis (OA) is a common chronic condition, and it can be difficult to manage. One treatment option that is being used involves intra-articular injection of hyaluronic acid, which relieves pain and stiffness through a process called viscosupplementation.
What is Osteoarthritis?
Osteoarthritis affects around 27 million people in the United States. This degenerative joint disease is caused by wear-and-tear of the joint’s cartilage, which is tissue that covers bone ends and provides cushion. Osteoarthritis is often caused by an injury to the joint, but it can be related to obesity or genetics. The most common symptoms of knee OA are joint pain, tenderness, loss of flexibility, and knee stiffness. Over time, bony growths occur around the joint, which can produce severe pain.
How does Hyaluronic Acid Work?
The exact mechanism of action of hyaluronic acid is not clear, but experts believe that increasing the amount of synovial fluid in the joint is key. With osteoarthritis, the knee joint cartilage erodes away, and bone ends often rub together. Synovial fluid is a naturally occurring solution that helps the knee joint bend smoothly and without pain. With OA, a reduction in the viscous and elastic properties of synovial fluid occurs. The concentration and molecular weight of synovial fluid decreases, which decreases lubrication and protection of joint tissues. Hyaluronic acid replaces the elastoviscosity to alleviate the pain of osteoarthritis.
Who is a Candidate for Hyaluronic Acid Injections?
Hyaluronic acid injections are considered for patients who continue to have significant knee symptoms despite traditional treatments like physical therapy and medications. In addition, hyaluronic acid injections are ideal for people who cannot tolerate nonsteroidal anti-inflammatory medications and other pain relievers due to gastrointestinal problems or allergies.
How are Hyaluronic Acid Products Made?
Most viscosupplements are derived from chicken and rooster combs. The combs are the fleshy crown on top of the rooster’s head, and they are processed and sterilized in the laboratory. Any patient with a known allergy to poultry, eggs, or chicken should avoid hyaluronic acid injections.
When will I notice the Benefits?
The benefits of hyaluronic acid injections are not immediate. It may take a few days to have pain relief. Immediately after the injection, some patients report an increase in knee pain, but this resolves within a few days. The greatest benefit of hyaluronic acid is usually felt 2-3 weeks after the injection. Most patients have effectiveness that last for 3-6 months.
Is Hyaluronic Acid Effective?
In a large randomized, double blind trial on the safety and efficacy of hylan G-F 20, patients with chronic OA knee pain were divided into two groups. One group received hyaluronic acid (treatment) and the other group received saline (control). The patients were evaluated after the injections and then again at 26 weeks post-therapy. The study found that participants who received the treatment had significant improvement in weight bearing, reduction in pain, and improvement with quality of life.
In another randomized controlled trial, researchers studied the short-term effects of intra-articular hyaluronic acid on isokinetic muscle force, proprioception, pain, and functional conditioning in participants with knee osteoarthritis. The study found that hyaluronic acid outperformed placebo 2:1. Pain scores were significantly decreased, and the researchers concluded that hyaluronic acid was a safe and effective treatment option.
Diracoglu D, Vural M, Baskent A et al. (2009). The effect of viscosupplementation on neuromuscular control of the knee in patients with osteoarthritis. J Back Musculoskelet Rehabil, 22: 1–9.
Wobig M, Dickhut A, Maier R, & Vetter G (2008). Viscosupplementation with hylan G-F 20: a 26-week controlled trial of efficacy and safety in the osteoarthritic knee. Clin Ther, 20: 410–423.