Statistics from the Arthritis Foundation indicate that more than 27 million people in the United States have osteoarthritis (OA). Among those individuals, the knee is a commonly affected joint. As we age, the cartilage that acts as a shock absorber in the knee joint wears away. Over time, the joint becomes rough, and the space between the bones decreases, resulting in pain and swelling. “Most patients come in, especially for their first visit, and will often have had no previous interventions,” says Jack Farr II, MD, an orthopedic surgeon at OrthoIndy in Indianapolis. “Physical therapy (PT), activity modification, and putting ice on the joint are all important things to try. Weight loss can also have a major impact.” The next step is using over-the-counter pain and anti-inflammatory medicines. Acetaminophen (Tylenol and others) is a simple over-the-counter pain reliever that can be effective in reducing arthritis pain. Nonsteroidal anti-inflammatory drugs (NSAID) may also be used; Ibuprofen (Advil, Motrin, and others) and naproxen (Naprosyn, Aleve, and others) are available both over the counter and by prescription. When considering using any self-administered drug, you should first check with your doctor to see whether any reason exists that would prohibit you from taking one or more of these medicines. This article explores knee injection options for osteoarthritis pain that are currently available; such as corticosteroids, viscosupplementation, platelet-rich plasma injections and stem cell injections.
Pain reduction is the number one goal of knee injections for osteoarthritis
Should these treatments fail to relieve discomfort, it may be time to consider knee injections. While these do work on both pain and swelling, there are limits to their efficacy.
“Our number 1 goal with any injectable medication is to reduce pain,” said David Jevsevar, MD, MBA, medical director for Orthopedics Clinical Program Development at Intermountain Healthcare in St. George, Utah.
“The secondary objective is to improve function and avoid stiffness when we can.”
In the United States, the first-line injectable medication is usually a corticosteroid. Although different ones can be used, cortisone (hydrocortisone) was the initial drug of the class and is often used as shorthand for corticosteroids in general.
“Cortisone shuts down the inflammation associated with knee OA flare-ups,” says Dr. Farr. “The medication shuts down the cascade of chemicals in the body that bring about the inflammation and calms down the joint. While the injection itself probably only lasts a few months, the results of interrupting the inflammatory process can last a long time.”
He says he has seen people who have gone back to their baseline state and been pain- and inflammation-free for years with one injection. Others have to come back a few times a year. However, some may see more limited success or even no success over time.
Knee injection options for osteoarthritis pain: Treatment results vary
How well individuals respond to the knee injections will depend largely on what is happening to them at the time of treatment. The more severe the OA, the less likely it is that relief will be long-lasting.
“Treatment results are variable,” says Jonathan Vigdorchik, MD, assistant professor of orthopedic surgery at NYU Langone Medical Center’s Hospital for Joint Diseases in New York City. “At our Joint Preservation and Arthritis Center, we’re doing clinical studies to identify which patients are going to get relief and which ones will have it last the longest. We just don’t know yet who will do well and who won’t.”
There also appear to be some diminishing returns with corticosteroid injections. As OA progresses, relief may decrease each time corticosteroids are used. Again, studies have yielded little information about who will respond the best or not all.
“We don’t really know how often you can give these injections,” says Dr. Jevesvar. “There is some concern about too many injections damaging the cartilage even further. Every three months, if needed, seems to be a safe number.”
Corticosteroid shots are contraindicated in people who have diabetes. This class of drugs can have a major impact on blood sugar levels.
The physicians stressed that it isn’t unusual to experience an increase in pain immediately after the shot is given—essentially, the corticosteroid may “stir things up” before the calming effects can take over. Any flare-up that occurs is usually over within 48 hours. However, it can be very disturbing to the person who doesn’t expect it.
If the increase in pain continues for more than 48 hours, talk to your doctor. You also should contact your doctor if there is increased swelling and redness in the knee, if you can’t move the joint, or if you have a fever and chills. These ailments could indicate an infection in the knee that needs to be treated immediately. (These complications are also seen following injections with other kinds of medicine.)
Viscosupplemenation is a controversial alternative to knee injections
A second injectable treatment is the viscosupplement. Hyaluronic acid (HA) is a part of the synovial fluid that surrounds, nourishes, and bathes the knee. Individuals with knee OA have been shown to have lower-than-normal levels of HA.
When this component is missing, the stickiness and elasticity of the synovial fluid changes. This in turn negatively affects joint lubrication and the joint’s ability to protect itself from shock and strain. The goal of viscosupplementation is to replace the HA and return the synovial fluid balance closer to normal.
There is currently some controversy about the usefulness of HA medications in the treatment of knee OA. Treatment guidelines from the American Academy of Orthopedic Surgeons (AAOS) in 2012 “strongly recommended” against the use of viscosupplementation.
“When we looked at the available studies, there is indeed a reduction in pain that is statistically significant,” says Dr. Jevsevar, who was chair of AAOS Committee on Evidence-Based Quality and Value that oversees clinical practice guidelines. “However, when we looked at clinical significance—whether the patient can actually feel a difference in pain—the difference from placebo wasn’t enough for the patient to notice it.”
Dr. Jevsevar says that people with OA should know that so far the evidence doesn’t show any real benefit, but he acknowledges some believe it works, and says that is fine for them. “Anything you put into a knee that contains fluid will work for a month,” he says. “We think this is probably because it dilutes the pain generators in the knee. This is the main plus we see with viscosupplementation.”
Other physician groups have not followed the AAOS lead in this controversy. Dr. Farr notes that the professional societies for sports medicine doctors and those who do arthroscopic surgery still maintain their earlier guidance.
“Writing guidelines entails a review all of the available literature on a subject,” he says. “The information is split into five categories, with randomized, placebo-controlled trials being the best. Their interpretation of the data was that the improvements were not big enough for them to say it definitely worked.”
Another group of experts could have a different take. Indeed, the letters to the editor and editorial pages of many doctor groups have been the venue for spirited discussions about the AAOS conclusions.
“The two important things to remember are that another set of experts can look at the same data and still conclude that HA had a use,” Farr says. “Also, that the AAOS did not say that it shouldn’t be used.”
Other treatments on the horizon for osteoarthritis include platelet-rich plasma injections
Other treatments are being studied for use in knee OA. One is platelet-rich plasma (PRP) injections. Platelets are the part of the blood that helps with clotting. They also release growth factors that help start healing.
In PRP injections, blood is taken from your arm and placed in a centrifuge that spins at high speeds to separate the various kinds of blood cells. The doctor takes the platelet-rich part of the blood and injects it into the knee.
The theory is that this will increase and concentrate the body’s natural healing ability. Enhancing these abilities helps people enjoy a faster and more thorough healing process that relieves symptoms and allows these individuals to return to their regular activities.
PRP has been successfully used in the operating room to help wound healing and stimulate bone formation. It is also being used, with great fanfare by some sports stars, to help baseball players with rotator cuff injuries. How well it will work for knee OA remains very much an open question.
“Doctors are doing PRP injections outside of clinical trials already,” said Dr. Vigdorchik. “We’re currently in the very early stages of research, so there is little literature about whether it will work or not for knee OA. No big clinical trials have been published, and we’re still trying to understand the basic science. While the treatments are available, the literature and the science aren’t yet in place.”
PRP is still considered experimental by most insurance companies. The injections, which can cost from $500 up to $2,000 each, often are not covered.
What information is available suggests few complications, mostly having to do with infections that can occur anytime an injection is given. Since it uses your own blood, there’s no concern about blood-borne infection or blood-type mismatch problems. In rare instances, the needle could go through a vein, causing bleeding, or a nerve, resulting in nerve damage.
Stem cells under study for possible osteoarthritis treatment
Stem cells—the only cells in the body that can change into other types of cells—are also being studied as a possible treatment. This is an option that in theory might stabilize or reverse the damage. Under specific circumstances, these cells can be changed into chondrocytes that could produce fresh cartilage.
A more common use for stem cells injected into the knee joint is to use them to “reset” the knee by rebalancing the interaction of pro- and anti-inflammatory chemicals. Some researchers also think that the injection of stem cells may concentrate the body’s natural repair efforts and speed up healing.
As with PRP, trials are at the very early stages. Most available studies use very small numbers of individuals and can’t be generalized to the larger population. However, Dr. Jevsevar does think that these early studies show some improvement in pain and function. The concern is whether this benefit will still be seen when more people are studied.
The bottom line from the experts is that corticosteroid injections remain the primary treatment for those with mild to moderate OA who haven’t responded to analgesic or NSAID therapy or other conservative measures such as weight loss, PT, or the use of ambulatory assist devices such as canes. The experts also stress that even the corticosteroid treatments only treat the pain and inflammation—they don’t stop or reverse the damage.
“OA is a disease process,” says Dr. Jevsevar. “After these treatments wear off, your knee is still arthritic and still generating the things that cause pain and discomfort. Eventually, they will overpower whatever you put in there. There is no cure.”
Learn more about osteoarthritis signs and symptoms here.
For the top 10 osteoarthritis self management tips, click here.