PT Classroom - Hyaluronic Acid Injections as a Form of Treatment for OA of the Knees  ׀ by Jill Bergersen, SPT


Osteoarthritis affects more than 21 million people in the United States and is the most prevalent form of arthritis seen (7). The knee, one of our body’s most critical joints, is the most commonly affected. Over the last decade hyaluronic acid joint injections have become a treatment option from those suffering from pain and stiffness associated with osteoarthritis of the knee (2). To better understand how these injections provide relief, one must first understand the workings of the knee joint, the purpose of cartilage, and the process of osteoarthritis. The knee is one of the largest and most complex joints of the body and is formed by the femur, tibia, and patella. Cartilage is a rubbery tissue that lines the ends of the bones at contact points to provide a cushion for the joint. Healthy cartilage acts as a shock absorber in the knee joint and provides a cushion for your bones as a means of protection against the impact forces that act on the body through walking, running, and possible falls. (3) Surrounding the knee joint there is a substance referred to as synovial fluid that contain the very important hyaluronan. The job of synovial fluid is to lubricate the joint by reducing the amount of friction to provide maximum movement. Within the synovial fluid is the hyaluronic acid which is a thick liquid that helps bones glide smoothly against one another (4). As this critical substance begins to break down, as seen in osteoarthritis, joint pain and stiffness become present due to the reduction of lubrication within the joint. In order for joints and cartilage to remain healthy there must be sufficient synovial fluid produced which is ultimately achieved through movement. As movement of the body is diminished due to pain or stiffness, less synovial fluid is present therefore the amount of lubrication decreases (1). A common analogy used to describe this concept is to think of a stiff door and when the door jams become dry the door doesn’t move as smoothly or easily. If you apply some WD-40 to lubricate the door jam you can then easily move the door. The same is true of your joints, when they become dry it is more difficult to move and with less ease then if they were properly lubricated. You must maintain your joints in the same way you maintain your home!

Osteoarthritis in the knee is caused by wear and tear to the joint leading to a gradual deterioration of cartilage. As the cartilage continues to wear down, the joint space decreases and the bones begin to rub together. In addition, the consistency of hyaluronan becomes thinner (6). The most common signs and symptoms of OA of the knee include joint pain, loss of mobility, stiffness, deformity, and tenderness (3). There is no cure for osteoarthritis and overtime the symptoms can become more severe indicating the importance for a treatment that can improve mobility and decrease the progression of OA. There are various treatment options that can yield different results for each individual. Initially, a more conservative approach is used by recommending patient’s to try exercise, physical therapy, and NSAIDS to relieve their symptoms (5). If those methods prove ineffective a more aggressive approach is used and one of those treatments is a hyaluronic acid injection. This treatment is noninvasive and is given in a series of weekly injections directly into the cavity around the knee joint over a 3 to 5 week period (7). The goal of these injections of hyaluronic acid into the knee joint is to replace some of the natural supply that has depleted due to the osteoarthritis. This added hyaluronic acid will increase lubrication of the joint making mobility easier and reduce pain by adding more cushion to the joint (7). The effects of the shot can last between six to twelve months before the possible return of OA symptoms.

There is some skepticism regarding the hyaluronic acid injection as an effective form of treatment for osteroarthritis of the knee, but research reveals more positive results than negative. In fact, it has been discovered that hyaluronic acid may play a larger role than originally thought within the joint. Recent research indicates that in addition to creating lubrication for the joint it also interferes with prostaglandins and cytokines, which promote inflammation (2). According to Dr. Moskowitz, a coauthor of Osteoarthritis Research Society International, “injecting supplemental hyaluronic acid may coax the joint into increasing the production of its own hyaluronic acid which in turn help to preserve cartilage (2).” In 2006, the most comprehensive review regarding knee osteoarthritis and hyaluronic injections was conducted and found that the average pain level was reduced by 28 to 54 percent in those who received the hyaluronic acid injection to treat their knee osteoarthritis (2). It also revealed that these individuals reported improvements in mobility and their ability to perform daily activities by 9 to 32 percent. Clearly, positive results are seen when patients utilize this non-invasive injection as treatment for their knee osteoarthritis.

Others may argue that the use of these injections provide no quick relief in comparison to the use of NSAID’s or corticosteroid injections. According to Bellamy’s Cochrane review it takes about five weeks before patients experience the full benefits of the hyaluronic injection as opposed to the few days when given a corticosteroid injection (2). Conversely, pain relief from corticosteroids lasts for a shorter time periods and overuse of these injections can actually cause cartilage to deteriorate further. In addition, the long term use of NSAID’s have been linked to the development of organ problems. Despite the length of time before pain relief is experienced, the hyaluronic injection still poses less detrimental side effects than other treatment options mentioned.

The larger studies conducted do have varying results concerning the level of pain relief individuals experience after a hyaluronic injection. Some patients were virtually pain free and had symptom relief for up to two years while others had no change in symptoms. This variation in response is common in these types of treatments and mostly reflects how the average person will respond. According to Dr. Altan, “we don’t know how to pick out those people who are going to have an outstanding response versus a modest response versus no response at all (2).” It is ultimately up to the patient to weigh the pros and cons of the procedure and see if it appeals to them and if they are willing to give it a try. Most importantly, patients need to accompany their injections with continued physical therapy. By reducing the knee pain associated with osteoarthritis through an injection, the patient will be able to gain greater ROM, progress to increasing strength, mobility, and balance through their therapy sessions. In doing so, individuals should see less frequency and intensity of symptoms if they return.

Depending on the severity of your condition, length of time with OA, and effectiveness or ineffectiveness of past treatments hyaluronic acid injections may be the next option. Injections are quick and painless making it an appealing option for individuals who have little success with other treatment methods. As with any treatment or procedure, it is important for the patient to research and educate themselves about the injections and determine if it is the right choice for them.

Last revised: August 19, 2014
by Jill Bergersen, SPT

1) American Academy of Family Physicians Family Doctor web site: "Osteoarthritis of the Knee: Hyaluronic Acid Injections." Karlsson, J et al, Rheumatology, 2002; vol 41: pp 1240-48.
2) Gower, Timothy. "Hyaluronic Acid Injections for Osteoarthritis." Hyaluronic Acid Injections. Arthritis Foundation, n.d. Web. 12 Aug. 2014.
3) Holland, Kimberly, and George Krucik, MD. "Viscosupplements for OA of the Knee: What You Need to Know." Viscosupplements for OA of the Knee: What You Need to Know. N.p., 2 May 2013. Web. 13 Aug. 2014.
4) Osteoarthritis. 9 April 2013. Mayo Foundation for Medical Education and Research. Retrieved August 12, 2014, from
5) Treatments & Procedures: Viscosupplementation. 30 Nov 2009. Cleveland Clinic. Retrieved August 12, 2014, from hic_viscosupplementation.aspx.

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