By Jonathan Chu, MD

Interventional Pain Medicine

PM&R

So maybe you’ve been suffering from knee pain lately, and your doctor has diagnosed you with osteoarthritis, which is essentially the most common, garden-variety of arthritis that results from wear and tear, mechanical stress, and overuse.

Well, first it’s important to know that you’re not alone, in that osteoarthritis affects 55 million people just in the United States, which is 23 percent of the population, and worldwide it’s actually considered to be the 4th leading cause of disability.

One of the most common and effective treatments for painful osteoarthritis of the knees is something called viscosupplementation, the most common ones being injections with the brand name compounds Synvisc and Euflexxa, and this may have even been a treatment suggested by your doctor.

Today, I’m going to talk about viscosupplementation injections and explain everything you need to know about the procedure, including what it is, how it works, what the potential benefits are, what the risks and potential adverse effects are, and what you can expect from the procedure overall.

So let’s get into it. 

First of all, to understand how viscosupplementation works, you first need to know how your knee works, so let’s do a quick overview of the anatomy.

Your knee joint is actually formed from the articulation of two different bones: the upper bone is the femur, which is your thigh bone, and the lower bone is your tibia, which is your shin bone. The knee is a hinge joint, which means exactly what it sounds like, in that it allows your knee to both flex and extend, but does not allow motion in other planes.

These two bones are lined with hyaline cartilage, which is a smooth, elastic, and very tough form of connective tissue, and they allow your femur and tibia to articulate against each other smoothly and easily. Sandwiched between the cartilage lining are two pads of fibrocartilage, which are known as the medial and lateral meniscus; most of you have probably heard  this term before, as surgeries to repair menisci are very common for younger athletes.

The entire joint is wrapped in a sheath of dense and tough fibrous connective tissue that is known as the joint capsule, or articular capsule, and this makes the joint a self-contained unit.

Now, contained within this capsule is a very vital substance known as synovial fluid. This is a thick and viscous fluid that really helps your joint function optimally by serving a few functions:

The first and most important is that it helps to reduce the friction between the cartilaginous surfaces, so that the joint can move smoothly and easily.

The second is that it helps with shock absorption, and by increasing the cushioning of the joint it helps to protect the joint.

Lastly, the synovial fluid also helps to nourish the cartilage of the joint with nutrients and also carry away waste products. 

Now next, let’s talk about osteoarthritis, the most common pain condition that affects the knee. In the very simplest terms, this is when the knee joint slowly breaks down over time due to years of wear and tear and overuse. This degeneration mostly involves the joint cartilage, but if it gets severe enough, it can also involve the bones of the joint as well, resulting in bone spurs and bony deformities and such.

Obviously, when someone is suffering from osteoarthritis, they are much more likely to develop a painful inflammation of the knee, especially after a bout of very strenuous activity or trauma. It’s important to note that having osteoarthritis doesn’t automatically mean that you also have pain, especially if the osteoarthritis is classified as mild or moderate. In general, it can be said that inflammation really is the key to pain, and this holds just as true for the knee than it does for any other part of the body.

Thus, it’s not surprising then that most treatments for painful osteoarthritis of the knee are designed to decrease the inflammation of the knee. Physical therapy is one mainstay, which involves strengthening the supporting musculature of the knee, and thus stabilizing the joint and hopefully decreasing the inflammation. The typical medications prescribed for knee osteoarthritis are known as NSAIDs, which stands for non-steroidal anti-inflammatory drugs, which would be your Advil and Naproxen, and also work by decreasing inflammation in the body.

So what happens if these oral anti-inflammatory medications and physical therapy exercises just aren’t enough? Then there’s a few different types of injections that you can try out before needing to consider surgery. For the patients I’ve taken care of, I’ve always tried my very best to help them exhaust every option before seriously considering surgery, as I think most people in general strongly prefer to be able solve their problem without surgery, if possible.

The most common type of knee injection is a corticosteroid injection, which is designed to quell the inflammation, and is usually quite effective at doing so.

The other major type of knee injection for knee osteoarthritis is an injection with viscosupplementation.

Now, in the very simplest terms, this injection is almost like injecting WD-40 into an old hinge to help it work more smoothly and better. It’s a gross oversimplification, but that’s essentially how it works.

Now if you remember from the discussion earlier, synovial fluid is essential to the proper functioning of your knee joint by helping to lubricate the joint and to provide cushioning. An essential component of this synovial fluid is something known as hyaluronic acid. Viscosupplementation, regardless of what brand of medication you use, involves the injection of compounds that are synthetic forms of hyaluronic acid into the knee joint, which serve to augment and bolster the natural lubrication of the joint. The most common brand names of hyaluronic acid injections are Synvisc-One and Euflexxa. I used both of them a lot during my residency and pain medicine fellowship, and I can’t say I really noticed any difference in efficacy between the two, which correlates to the data in the medical literature. However, I would say that between the two brands I do prefer Synvisc-One, since as the name says, it only requires one injection, whereas Euflexxa is a series of 3 injections, usually done over a period of 3 weeks.

In terms of how doctors can perform knee injections, there’s really 3 main methods.

The first is that you can do them just using anatomical landmarks for guidance. I’ve done many hundreds of knee injections this way, and it’s really quick and easy for the patient and usually works quite well the vast majority of the time.

However, in general, I reserve unguided knee injections for steroid injections only. However, viscosupplementation injections are a little more involved, so I personally prefer to use image guidance for the increased accuracy and to really ensure that the hyaluronic acid fully gets into the joint capsule.

The two types of image-guidance you can use to assist with knee injections would be ultrasound guidance and fluoroscopic guidance. With ultrasound guidance, your doctor will guide the needle into the joint capsule under real-time ultrasound guidance. With fluoroscopic guidance, your doctor will use x-ray imaging to guide the needle into the joint capsule, and then usually inject a cc or two of contrast dye to confirm that they’re inside the joint, before injecting the hyaluronic acid.

 Now let’s talk about efficacy, which is what the majority of patients are most interested in, and probably the most important part of this video.

When you look into the literature regarding viscosupplementation, you’ll actually find quite a few meta-analyses and reviews that come to a variety of different conclusions regarding efficacy. Some of them conclude the viscosupplementation only has minimal benefit over placebo and that the support for its usage is inconclusive, while on the other hand, you’ll also find many others that do show that these injections provide significant pain relief and can even delay the need for surgery for years.

For example, Rutjes and colleagues in 2012 completed a systematic review and meta-analysis that was published in the Annals of Internal Medicine, and they came to the conclusion that benefit from viscosupplementation was clinically irrelevant overall.

On the other hand, there have also been a number of major studies and reviews that did show that viscosupplementation had a definite benefit. For example, Waddell and colleagues examined a cohort of over 1,800 patients, and found injections with Synvisc, also known as hylan G-F20, allowed 75 percent of those patients to delay the need for total knee replacement by 7 years or more. Another example is Keary and colleagues, who demonstrated that injection with Syvisc, or hylan G-F20, led to significant improvements in both pain and function, at both the 3 month and 6 month mark after the procedure.

Furthermore, Richette and colleagues performed an extensive meta-analysis in 2015 that concluded that viscosupplementation provided a definite moderate-level benefit for patients with painful knee osteoarthritis.

So overall, when you take a deep dive into the medical literature regarding viscosupplementation, you’re going to come across a mixed bag of conclusions, with some studies and reviews showing viscosupplementation offers minimal benefit over placebo, while you will also find many others that show significant benefit. However, that being said, the general trend seems to be that the evidence supporting the use of viscosupplementation for knee osteoarthritis has been steadily growing over the past one to two decades.

Moving away from the big studies and reviews, just from my own experience, I’ve found that viscosupplementation to be an excellent treatment option for properly selected patients. That would be patients with mild to moderate osteoarthritis of the knee, who just have not gotten enough pain relief with oral non-steroidal anti-inflammatories and physical therapy, and who are not interested in surgery. This can also include patients with GI issues or who are on blood thinners, and hence cannot tolerate oral NSAIDs, and need an alternative treatment.

In general, the consensus is that viscosupplementation tends to be less effective for people with stage 4 osteoarthritis, which is the most advanced form of osteoarthritis, which really makes sense logically, since in that scenario there is just not a lot less cartilage left to lubricate, though in certain scenarios it can definitely still be worth a try.

Now in terms of potential adverse effects, overall, injection with viscosupplementation is a very safe procedure. A small percentage of patients can develop swelling, heat, redness, and increased pain in the knee after the injection, and this is because the immune system can react to the compounds in the injection and develop an inflammatory response. Most of the time, even if increased inflammation does occur, it’s quite mild and limited in duration. Now, as with any other joint injection, the most serious potential complications would be an infection of the joint or significant bleeding into the joint; however, as long as the procedure is done with proper sterile technique, these types of complications are extremely, extremely rare.

Overall, injections with viscosupplementation are procedures that I really like, and as I said earlier, are usually very effective in the right patients for improving pain, function, and quality of life. In people with a mild to moderate degree of knee arthritis, it’s a really useful tool in the toolbox to have, alongside oral medications, and of course physical therapy, a dedicated home exercise program, and weight loss.

Now, in my opinion, it’s very important that you utilize this injection as part of a multimodal plan, since the effects of the injection usually last about 5-6 months, and most people do not want to keep getting injections for the rest of their lives. Thus, I think it’s really important to take advantage of the period of pain improvement after this injection by taking your physical therapy and home exercises very seriously, rebuilding the strength of the surrounding muscles of your knee, which will stabilize your knee joint and protect it moving forward. Also, if you do get effective pain relief from the injection, I think that it’s an awesome time to take up some type of low impact cardiovascular exercise, such as the stationary bike, or the elliptical machine, or even pool walking, which will not only build up your cardiopulmonary conditioning, but also hopefully help you lose excess weight, which will also really help to offload load your knees and improve your pain in the long term, and also slow the progression of your osteoarthritis. That being said, the procedure can be safely repeated if needed, and if you find that you need to get Synvisc injections twice a year in the long-term to keep you going and functioning well, that’s definitely okay too.

Anyway, thanks so much for watching and I hope you found the video valuable. If you did, feel free to like and subscribe, and also check out the official 360 Pain Academy website, linked below, which has lots of free articles and educational content. This is Dr. Chu, founder of 360 Pain Academy; take care until the next video.

References:

Benzon, H. T., et al. (2018). Essentials of pain medicine (4th ed.). Elsevier.

Braddom, R. L. (Ed.). (2010). Physical medicine and rehabilitation (4th ed.). Saunders/Elsevier.

Cuccurullo, S. J. (2004). Physical medicine and rehabilitation board review. Demos Medical Publishing.

Kearey P, Popple AE, Warren J, et al. Improvement in condition-specific and generic quality of life outcomes in patients with knee osteoarthritis following single-injection Synvisc: results from the LOBRAS study. Curr Med Res Opin. 2017;33(3):409-419.

Netter, F. H. (2006). Atlas of human anatomy (4th ed.). Saunders/Elsevier.

Peck, J., Slovek, A., Miro, P., Vij, N., Traube, B., Lee, C., Berger, A. A., Kassem, H., Kaye, A. D., Sherman, W. F., & Abd-Elsayed, A. (2021). A comprehensive review of viscosupplementation in osteoarthritis of the knee. Orthopedic Reviews, 13(1), e25549.

Richette P, Chevalier X, Ea HK, et al. Hyaluronan for knee osteoarthritis: an updated meta-analysis of trials with low risk of bias. 2015;1(1):e000071.

Rutjes AWS, Jüni P, da Costa BR, Trelle S, Nüesch E, Reichenbach S. Viscosupplementation for osteoarthritis of the knee: a systematic review and meta-analysis. Ann Intern Med. 2012;157(3):180-191.

Waddell DD, Joseph B. Delayed Total Knee Replacement with Hylan G-F 20. J Knee Surg. 2016;29(2):159-168.