Hyaluronic Acid injection, which is also known as Hyaluronan, is a type of substance naturally found in the synovial joints in the body. The main function of this viscoelastic substance is that it acts as a shock absorber in the joints and helps dissipate energy after a trauma. Hyaluronic Acid also helps in the lubrication of the joint, hence promoting the movement of the body and aiding in pain relief. (1)
Studies have shown hyaluronic acid injections in the joints to have an anti-inflammatory action on the surrounding cells along with preventing the death of the cartilage cells in arthritic patients and improving their quality of life. (2)
Osteoarthritis and Hyaluronic Acid Content
It has been found that patients with Osteoarthritis have a reduced concentration and molecular weight of Hyaluronic Acid in the synovial fluid of their joints. Since the functioning of the synovial fluid in the joints is highly dependent on the Hyaluronic acid content, a reduction in the hyaluronic Acid leads to a reduction in the viscoelastic properties of the synovial fluid and hence leading to a degradation of the joint. (3) This is what led to the initial suggestion that Hyaluronic Acid knee injections by an Orthopedic specialist might be effective at restoring the viscoelastic and natural protective function of the synovial fluid in the knee joint space.
These injections help the patient by increasing their joint lubrication and acting as the shock absorbs, allowing them to reduce overall knee pain levels. They are particularly suggested for those who have undergone other treatment modalities like taking pain medication like Acetaminophen, and physical therapy had not seen any positive results.
How Long Do Hyaluronic Acid Knee Injections Last?
It has generally been suggested that Hyaluronic Acid Knee injections with higher molecular weight can last up to 1 year. These injections may also be repeatedly safely every six months to a year for the management of Osteoarthritis. However, the exact longevity of Hyaluronic acid knee injections is still being investigated in musculoskeletal systematic reviews and meta-analysis. One recent study showed they last for more than 450 days in some individuals, while for the others, It lasted for more than 1000 days. (4)
Another study, which included 223 individuals, showed positive results after the injection of Hyaluronic Acid. It was found that the participants who had undergone these injections had lower joint pain and stiffness levels than those who were not injected. The study concluded by stating that the Hyaluronic Acid knee injections were effective for mild to moderate knee arthritis symptoms for at least 13 weeks after the injection period. (5)
What Are The Side Effects of Hyaluronic Acid Knee Injections?
The rare side effects associated with Hyaluronic Acid Knee Injections are almost always mild and self-limiting. The most common of these may include slight irritation at the injection site or a mild flare-up in less than 2% of individuals. This may include symptoms like pain, swelling, and redness, which can be corrected with icing, anti-inflammatory pills, and rest. There have been no reports of joint infections after Hyaluronic Acid Injections in clinical trials that have been conducted to study the subject matter. Systemic side effects like rashes, myalgia, nausea, and muscle cramps are also very rare and reported in less than 2% of the participants in the clinical trials. (6)
What Is the Best Injection For Knees?
Experts have generally suggested that Hyaluronic Acid injections with a higher molecular weight like Hyalgan are considered better as they are much more long-lasting. This is because they are FDA-approved and more cross-linked and have a higher viscosity, making their degradation much slower as compared to other forms of Hyaluronan injections, which are less cross-linked and have a lower molecular weight.
What is the Difference between Hyaluronic Acid and Cortisone?
The effect of Hyaluronic Acid injections for knee osteoarthritis is often compared to the effectiveness of Cortisone injections – however, they are not the same. Cortisone is an anti-inflammatory substance that is prescribed by doctors most commonly for the Osteoarthritis of the knees to improve swelling, pain, and inflammation. Even though some evidence shows these injections to work for up to 3 months, they are not effective in all cases. Moreover, unlike Intra Articular Hyaluronic Acid Injections which are considered safe to be re-injected, Cortisone injections may lead to cartilage loss on reinjection. It may also promote the degradation of joints until the individual requires joint replacement and has to undergo total knee replacement surgery.
Another difference between the two is that while the effectiveness of Cortisone may be immediate, it may take up to 4 weeks for the Hyaluronic Acid injections to become effective. However, this also means that the effects of Hyaluronic Acid injections are much longer. (7)
Hyaluronic Acid Knee Injections have been discussed and investigated by numerous recent studies, the majority of which have found them to be effective at treating the symptoms of mild to moderate knee osteoarthritis. They are ideal for individuals who don’t have significant swelling or inflammation of the joint, as the injections take a few days to show results. Hence if you are someone who is looking for a quick fix, these injections might not be for you. On the other hand, if you are willing to wait a few days to have longer-lasting results, the Hyaluronic Acid Knee Injections are ideal for you. These are also suggested for individuals who are allergic to steroids or may not be permitted to use them for certain medical conditions. They have no downtime, so the individual may go home right after getting their injection.
- Altman, R. D., Akermark, C., Beaulieu, A. D., Schnitzer, T., & Durolane International Study Group (2004). Efficacy and safety of a single intra-articular injection of non-animal stabilized hyaluronic Acid (NASHA) in patients with Osteoarthritis of the knee. Osteoarthritis and cartilage, 12(8), 642–649. https://doi.org/10.1016/j.joca.2004.04.010
- Larsen, N. E., Lombard, K. M., Parent, E. G., & Balazs, E. A. (1992). Effect of hylan on cartilage and chondrocyte cultures. Journal of orthopaedic research : official publication of the Orthopaedic Research Society, 10(1), 23–32. https://doi.org/10.1002/jor.1100100104
- Dahl, L. B., Dahl, I. M., Engström-Laurent, A., & Granath, K. (1985). Concentration and molecular weight of sodium hyaluronate in synovial fluid from patients with rheumatoid arthritis and other arthropathies. Annals of the rheumatic diseases, 44(12), 817–822. https://doi.org/10.1136/ard.44.12.817
- Carney, G., Harrison, A., & Fitzpatrick, J. (2021). Long-Term Outcome Measures of Repeated Non-Animal Stabilized Hyaluronic Acid (Durolane) Injections in Osteoarthritis: A 6-Year Cohort Study with 623 Consecutive Patients. Open access rheumatology : research and reviews, 13, 285–292. https://doi.org/10.2147/OARRR.S331562
- Day, R., Brooks, P., Conaghan, P. G., Petersen, M., & Multicenter Trial Group (2004). A double blind, randomized, multicenter, parallel group study of the effectiveness and tolerance of intraarticular Hyaluronan in Osteoarthritis of the knee. The Journal of rheumatology, 31(4), 775–782.
- Walker K, Basehore BM, Goyal A, et al. Hyaluronic Acid. [Updated 2021 Nov 15]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK482440/
- Leopold, S. S., Redd, B. B., Warme, W. J., Wehrle, P. A., Pettis, P. D., & Shott, S. (2003). Corticosteroid compared with hyaluronic acid injections for the treatment of Osteoarthritis of the knee. A prospective, randomized trial. The Journal of bone and joint surgery. American volume, 85(7), 1197–1203. https://doi.org/10.2106/00004623-200307000-00003