Patients in the NHS may manage OA symptoms in the early stages conservatively with analgesic medication, steroid injections, exercise, physiotherapy and weight reduction. There is an imperative to reduce opioid use for persistent pain, due to addiction risk, side effects and long-term increased sensitivity to pain. There is growing evidence to refute the usefulness of steroid injections in weight bearing joints, with potential deleterious effects upon articular cartilage in the longer term. Access to physiotherapy and weight management services may be challenging or significantly delayed due to rising waiting lists. There’s a notable shortage of non-pharmacological injectable treatments that are both clinically effective and affordable, leading to a growing treatment gap in the NHS for those living with mild to moderate OA.  That coupled with a mandate to move towards personalised care, shared decision making and supported self- management for long term diseases, there is a growing need for innovation in the treatment of OA within primary care settings without medication or surgical procedures.

Self-funding patients have more non-pharmacological injectable treatment options, such as hyaluronic acid (HA) viscosuplementation injections. HA injections aim to restore synovial fluid function of lubrication and shock absorption, which is lost due to the OA disease process. Natural synovial fluid should seamlessly move from lubricating to shock absorption function, depending on the state of the joint. We know there is a loss of hyaluronic acid in synovial fluid in OA, with age and following joint injury. There are conflicting opinions regarding the clinical efficacy of hyaluronic acid, with preparations known to have longevity in situ of only a few days in most cases. Nonetheless, there is research to support that injecting hyaluronic acid into an arthritic joint may improve pain and function from anywhere between 2-26 weeks. HA is not a panacea to managing OA, with most studies showing improvement in pain and function in mild to moderate OA only.

The HA market in the UK has seen very little change over the last 20 years with linear and cross-linking HA structures only available. These earlier versions of HA are not without limitations. High molecular weight HA preparations whilst restore some shock absorption function, they are limited in the lubrication function due to the increased viscosity and rigidity of the device. Low molecular weight is lower in viscosity so provides lubrication but does not effectively achieve shock absorption function. Linear preparations are thought to be sensitive to early breakdown from hyaluronidase, and chemical cross linking whilst improves resistance, may cause some irritation post injection, temporarily increasing pain and stiffness in some cases. Neither linear nor cross-linked preparations can exceed a concentration of around 2.4% high molecular weight HA due to the viscosity of the fluid and difficulty in passing through the needle.

GAG: glycosaminoglycan

References

Musculoskeletal Health: A 5 year strategic framework for prevention across the lifecourse Department of Health and Social care working with Public Health England and Department for Work and Pensions. (n.d.). Available at: https://assets.publishing.service.gov.uk/media/5d0b44eded915d0939f84803/Musculoskeletal_Health_5_year_strategy.pdf.

NHS England (2023). NHS England» Optimising Personalised Care for Adults Prescribed Medicines Associated with Dependence or Withdrawal Symptoms. [online] www.england.nhs.uk. Available at: https://www.england.nhs.uk/long-read/optimising-personalised-care-for-adults-prescribed-medicines-associated-with-dependence-or-withdrawal-symptoms/.

‌Zeng, C., Lane, N.E., Hunter, D.J., Wei, J., Choi, H.K., McAlindon, T.E., Li, H., Lu, N., Lei, G. and Zhang, Y., 2019. Intra-articular corticosteroids and the risk of knee osteoarthritis progression: results from the Osteoarthritis Initiative. Osteoarthritis and cartilage, 27(6), pp.855-862.

Pereira T V, Jüni P, Saadat P, Xing D, Yao L, Bobos P et al. Viscosupplementation for knee osteoarthritis: systematic review and meta-analysis BMJ 2022; 378 :e069722 doi:10.1136/bmj-2022-069722

Maheu E et al. Efficacy and safety of hyaluronic acid in the management of osteoarthritis: Evidence from real-life setting trials and surveys. Semin Arthritis Rheum. 2016 Feb;45/4 Suppl):S28-33.

Snetkov P, Zakharova K, Morozkina S, Olekhnovich R, Uspenskaya M. Hyaluronic Acid: The Influence of Molecular Weight on Structural, Physical, Physico-Chemical, and Degradable Properties of Biopolymer. Polymers (Basel). 2020 Aug 11;12(8):1800. doi: 10.3390/polym12081800. PMID: 32796708; PMCID: PMC7464276.