When it comes to arthritis of the knee, tens of millions of Americans suffer from the problem annually. Over 300,000 knee replacements are performed every year in the US. Along with the regular wear and tear type of arthritis, known as osteoarthritis, there are also a lot of younger individuals who have suffered a trauma in the past and now have post traumatic arthritis. Being in a younger age group and dealing with knee arthritis nonsurgically is crucial, as knee replacements do not work exceptionally well long term in younger individuals. They are really only meant to last 10 to 20 years and then often a revision is necessary. Therefore having effective injection options for patients young and old is therefore imperative for successful treatment since a knee replacement should be considered a last resort, quality of life decision.
WHAT KIND OF KNEE INJECTIONS ARE AVAILABLE TO PATIENTS?
When regular treatments are not working well enough such as medication management with nonsteroidal anti-inflammatories along with physical therapy, intra-articular injections can be a great option. Corticosteroid injections (aka steroid or cortisone) were first introduced in the 1950s for joint injections, most commonly for rheumatoid arthritis (inflammatory arthritis). They work very well for RA patients with affected knees, and a few decades later it was discovered they helped relieve the pain of osteoarthritis as well (wear and tear degenerative arthritis). Once steroid injections were utilized in osteoarthritis patients, initial studies were performed on small animals which showed harmful effects on their cartilage. However, subsequent studies in larger animals showed none of these issues so their popularity blossomed for human Injection and has continued to this day. Cortisone is the “gold standard” for pain management knee injections. There are additional knee injection substances available including hyaluronic acid substances (e.g. Synvisc, Orthovisc, Hyalgan), which have shown some beneficial effects in numerous studies and are discussed below.
HOW WELL DO CORTISONE INJECTIONS IN THE KNEE WORK?
When cortisone is injected into the knee, it alleviates some of the pain associated with arthritis. Cortisone is a hefty anti-inflammatory medicine, and it is now known that some of the pain from arthritis comes from inflammation. Multiple studies over the last few decades have consistently shown favorable results from steroid injections for arthritis patients, usually achieving over a 75% good to excellent result (Ozlurk et al. Rheumatol Int, 2006). Most individuals experience a striking relief of their pain associated with a substantial increase in range of motion. Steroid injections into the knee may be repeated every few months with the expectation that pain relief will be achieved again. If an individual’s arthritis substantially worsens, the beneficial effects seen may not be good enough, eventually necessitating a knee replacement.
WHAT ARE HYALURONIC ACID INJECTIONS FOR KNEE ARTHRITIS?
There is a substance known as hyaluronic and that is naturally found in the synovial fluid of human knee joints. It works to lubricate and cushion the knee joint, being the human equivalent of “motor oil”. In 1997 the FDA approved the first hyaluronic acid preparation made from rooster combs for usage in knee injections for osteoarthritis. Currently there are multiple FDA approved hyaluronic acid preparations, which are all extracted from rooster combs. They have trade names such as Hyalgan, Synvisc and Orthovisc. While each company counts the benefits of their individual product, research studies have shown that all of them work consistently well while no one particular brand has shown superiority (Kotevoglu et al, Rheumatology Int 2006). These injections are also called viscosupplementation as they restore the normal viscoelastic properties to synovial fluid. This can help protect cartilage, lubricate the joint and improve the shock absorbing effect of the knee. It is also suspected that hyaluronic acid injections may protect cartilage cells and actually promote the formation of more cartilage. This is the subject of a lot of speculation and has not been definitively proven.
HOW ARE KNEE INJECTIONS PERFORMED?
Injections into the knee are performed in an office setting. It is not necessary to have x-ray assistance with the injections as the joint is not far from the surface of the skin. There are various methods that doctors will use to approach the joint, with differences coming down to how an individual doctor was trained along with typically going into the side of the knee joint that has a more open joint space. Often times the surface of the skin is numbed with a spray, and then some numbing medicine is injected just under the skin. Once the needle is inside the knee joint, the doctor will often aspirate fluid from the knee in preparation for putting the numbing medicine and injection material back into the joint. The injected material typically consists of a numbing medicine such as Lidocaine along with a corticosteroid such as Kenalog. With steroid injections into the knee, they should not be performed more than once every few months. With hyaluronic acid injections, they often require a series performed one week apart for 3 to 5 weeks (so it’s 3 to 5 injections total). Every 6-12 months, hyaluronic acid injections may be repeated.
HOW OFTEN CAN KNEE INJECTIONS BE PERFORMED?
Stir injections into knee should not be performed more than a few times a year. While the steroid injected into the knee pretty much stays in the knee, a small amount does get absorbed into the bloodstream and may cause slight blood sugar elevations and some other transient symptoms. The hyaluronic acid injections, however, often involve a series of injections which should not be repeated more than a couple times a year.
HOW EFFECTIVE ARE KNEE INJECTIONS FROM ARTHRITIS?
Knee injections are typically extremely effective. Steroid injections into the knee have over 80% good to excellent results for pain relief, and hyaluronic acid injections have shown over 80% satisfactory results as well which was maintained for over a six-month time period (Keith MP, Am J Orthop. 2012). These results are often good enough to delay the need for a knee replacement surgery or avoid it altogether.
WHAT ARE THE RISKS OF A KNEE INJECTION?
A knee injection is a low-risk procedure, but it is not a risk free procedure. There is a small risk of infection, at about 0.1%. There’s also a risk of provoking serious bleeding if the patient is receiving anti-clotting medication. So that should be stopped a few days prior to the injection, your doctor will tell you how long exactly. Steroids may cause temporary issues with blood sugar along with some weight gain and water retention. These are usually very temporary side effects since they are locally injected and only a minor amount gets absorbed into the bloodstream. At times an individual may complain of increased warmth and some flushing of the skin. A complication of hyaluronic acid injections may include what is called a pseudo-infection. This occurs for unknown reasons and appears to look like a real infection, but it actually is just an inflammation reaction of the skin and does not require active treatment.