When lifestyle changes and other remedies do not relieve the pain of osteoarthritis in the knee, injections may help. Howard LeWine, M.D. of Harvard Health describes the two main types of injections for knee osteoarthritis.
Question: I have osteoarthritis in both knees. The left knee is especially painful and stiff. When should a person consider getting knee injections?
Answer: People can often manage the pain and improve mobility with lifestyle changes, such as weight loss, physical therapy, and exercises focusing on joint movement and strengthening leg muscles. Taking occasional over-the-counter or prescription pain relievers or anti-inflammatory medicines also can help. These can be taken in pill form or topically (applied to the skin).
But if these strategies don’t offer sufficient relief, or if symptoms impede your ability to move freely, an injection can provide immediate pain relief, reduce inflammation, and increase mobility.
But not everyone improves, and even if they are helpful, injections are a temporary treatment that won’t cure your knee osteoarthritis or change the course of the condition. If you must rely on repeated injections for pain management and help with mobility, then it’s probably time to consider a knee replacement.
There are two main types of injections for knee osteoarthritis: corticosteroids and hyaluronic acid.
Corticosteroid injections (also known as steroid shots) contained a manufactured drug that resembles cortisol, a hormone the adrenal glands produce. They reduce inflammation, pain, and swelling in and around the knee joint. If the knee is swollen, your doctor may first remove excess fluid with a needle.
Joints are surrounded by synovial fluid, which helps cushion and lubricate the moving parts of the knee. However, when cartilage is damaged from osteoarthritis, the body responds by overproducing synovial fluid, which leads to swelling. Removing fluid relieves pressure and swelling around the knee joint and makes the steroid injection more effective.
Once any excess fluid is removed, the corticosteroid (usually mixed with a numbing agent) is injected into the knee joint. Relief from the numbing agent kicks in right away, while the corticosteroid takes about 24 hours to start working on your symptoms.
The corticosteroid injection’s effect can last from several weeks to months. Repeat injections can be given every three to four months. But over time, they may work less well and for shorter periods.
A hyaluronic acid injection is usually recommended if corticosteroid injections don’t work, or the person needs to avoid injected corticosteroids.
Hyaluronic acid is a natural component of the synovial fluid in the joints. As osteoarthritis advances, hyaluronic acid decreases, which makes synovial fluid thinner and less effective. This can increase pain and stiffness, as there’s less lubrication to help the knee joint move freely. The synthetic hyaluronic acid acts like oil on a rusty joint.
If the hyaluronic acid injection provides significant benefit, a follow-up injection may be given after six months.
Howard LeWine, M.D., is an internist at Brigham and Women’s Hospital in Boston and assistant professor at Harvard Medical School. For additional consumer health information, please visit www.health.harvard.edu.
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Read more about osteoarthritis on Seniors Guide:
Osteoarthritis in Hips and Knees