What You Need to Know About Gel Injections

A popular treatment for the symptoms of osteoarthritis (OA) – pain, swelling, aching – is the use of an injection often referred to as a “gel injection” or hyaluronic acid.

But most people receiving these injections don’t know much about how they work and doctors rarely have time to explain. Usually, it’s something like “It’ll make your (knee, hip) feel better” and well, that’s what people are after.

OA is a disruption, an imbalance,  in the chemical environment of the joint leading to a gradual destruction of the protective lining covering the bones – cartilage – and development of symptoms. You might have evidence of cartilage loss on an X-Ray or MRI but that doesn’t mean you will necessarily have symptoms. I’ve had many clients who had joint changes on imaging studies yet were able to re-establish homeostasis in the joint and return to an active life.

Inside your joint, let’s use the knee as an example, you have a thin lining of cells known as the synovium. This lining produces a fluid – synovial fluid – which helps reduce friction so your joint moves smoothly and also helps reduce the force -acting like a biologic shock absorber-that travels into the joint from weightbearing.

Synovial fluid has a consistency of an egg white until you start moving the joint at which point the viscosity changes to allow for motion. One of the problems associated with osteoarthritis is a thinning of this fluid at rest and every thinner with movement. This results is less protection of the joint surface from force and more friction.

Joints don’t like friction. Or excessive pressure. Clients would often note that their knee would hurt while, for example, walking down a flight of stairs. This is from the increase in pressure in the joint. Or, they notice that sitting in a long meeting or a movie that their knee would feel stiff or ache. This is from the reduced thickness of the fluid. The result is symptoms such as swelling, aching, stiffness, and/or pain.

One of the components of synovial fluid is hyaluronic acid (HA). It also is in skin and other connective tissues. It’s the HA that gives synovial fluid its protective qualities.

HA injections – gel injections – counteract the diminished quality of the synovial fluid. It makes the fluid thicker and reduces friction in the joint.

But why does the synovial fluid become less viscous or thinner  in the first place?

One main reasons is chronic inflammation. The inflammation interferes with the production of HA by the cells of the synovium. Less HA means a thinner, less viscous synovial fluid.

HA injections can modulate the degree of inflammation which tends to reduce symptoms and there’s some evidence that the injections can stimulate cartilage cells to improve the structural integrity of cartilage and inhibit certain enzymes that would degrade the joint surface.

Do the injections work and, if so, for how long?

Gel injections has been studied extensively and the bottom line is that the clinical effectiveness varies quite a bit. The reasons for the variability include the formulation of the gel, the timing of the injection (severity of symptoms, presence of swelling) and the outcome measures used to determine the effectiveness. Improvement of symptoms for up to 6 months is common but, again, the degree of improvement varies.

So, in other words, gel injections help some people for a while – up to six months – and don’t help other people at all.

Something that has not been studied or even considered is what happens – physically – after the gel injections. Most people are given vague advice such as “just take it easy for a while” or “use common sense”.

Keep in mind that the gel injections temporarily change your joint’s  biochemical environment but the underlying problem – OA – is still there.

Something I’ve seen many times is, after a gel injection and a substantial improvement of symptoms, people just go back to their daily routine including exercise or active hobbies or sports. It’s understandable since they feel better but what might be even more advantageous would be to work on improving the health and strength of the joint especially since symptoms will be less likely to get in the way.

The goal is to improve the quality of your synovial fluid. Gel injections can do that for a time but you can also improve the synovial fluid with diet, certain exercises and movements. Of course, the more natural approach – exercise and movement – takes longer. The positive acute change produced in the fluid from the exercise will gradually become a more chronic change over time. This phenomenon happens with other bodily tissues such as muscle, tendon, ligament, bone (for details on how to maximize improvements for knee gel injections, click here ).

Your body responds to controlled movement in a positive way. So, if you choose the HA injection route, why not add some exercise and movement to enhance the changes inside your joint?

REFERENCES:

• Balazs, E. A., Denlinger, J. L., Naftchi, N. E. (1974). Viscosupplementation: A new concept in the treatment of osteoarthritis. Journal of Rheumatology, 1(1), 3-12.
• Gigante, A., & Callegari, L. (2018). The role of intra-articular hyaluronan (Sinovial(®)) in the treatment of osteoarthritis. Rheumatology International, 38(10), 1923-1931.
• Jevsevar, D. S. (2013). Treatment of osteoarthritis of the knee: evidence-based guideline, 2nd edition. Journal of the American Academy of Orthopaedic Surgeons, 21(9), 571-576.
• Loeser, R. F., Goldring, S. R., Scanzello, C. R., & Goldring, M. B. (2012). Osteoarthritis: A disease of the joint as an organ. Arthritis and Rheumatism, 64(6), 1697-1707.
• Smith, M. M., & Ghosh, P. (2009). The synthesis of hyaluronic acid by human synovial fibroblasts is influenced by the nature of the hyaluronate in the extracellular environment. Rheumatology International, 29(11), 1311-1318.
• Wang, C. T., Lin, Y. T., Chiang, B. L., & Lin, Y. H. (2006). Molecular regulation of the effect of hyaluronic acid on the anti-inflammation and anti-apoptosis in human osteoarthritis chondrocytes. Arthritis Research and Therapy, 8(4), R616.
• Wang, X., Hunter, D., Xu, J., & Ding, C. (2014). Metabolic triggered inflammation in osteoarthritis. Osteoarthritis and Cartilage, 22(7), 1157-1165. Shen, Y., Ruan, H., Wang, L., Li, Y., & Luo, R. (2021). The potential mechanisms underlying the therapeutic effects of hyaluronic acid injection for osteoarthritis: A systematic review and meta-analysis. Journal of Orthopaedic Translation, 27, 120-129.
• Ghosh, P., Guidolin, D., & Spector, M. (2008). Biochemistry of osteoarthritis. Current Opinion in Rheumatology, 20(5), 544-550.

Thanks for reading.

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Doug Kelsey has been a physical therapist and human movement expert since 1981. He is formerly Associate Professor and Assistant Dean for Clinical Affairs at the University of Oklahoma Health Sciences Center and the author of several books. He has conducted over 250 educational seminars for therapists, trainers, physicians, and the public and has presented lectures at national and international scientific and professional conferences. His professional CV is here.