Knee osteoarthritis (OA) is a prevalent degenerative joint condition that affects millions of people worldwide. It is characterized by the breakdown of cartilage, leading to pain, stiffness, and reduced mobility. In recent years, injection therapies such as platelet-rich plasma (PRP) and hyaluronic acid (HA) have gained popularity as potential treatment options for knee OA, whilst corticosteroid injections have been utilised for much longer.
This blog post aims to critically examine the efficacy of injection therapy for knee OA. Injection therapies are not recommended as first line treatments, due to a lack of definitive evidence for these injections, but rather can be used when improvements with first line treatments are deemed insufficient. Clinicians should consider individual patient factors, preferences, and cost-effectiveness when selecting the most suitable injection therapy for knee OA. As with any medical intervention, a comprehensive evaluation of the patient’s condition and a shared decision-making approach between healthcare providers and patients are crucial for optimal treatment outcomes. Due to the short term improvements in pain and function, which vary from weeks to months, injection therapy should NOT be viewed as a stand-alone treatment, but rather should occur in tandem with other treatments such as physiotherapy and exercise.
Corticosteroid injections are usually given in tandem with a local anaesthetic and appear to offer some short relief of pain due to a reduction in inflammation within the joint. Studies report improvements in symptoms varying from 5-15 weeks, and thus repeated desire for injection is common. Controversy exists regarding the detrimental effects on bodily tissues with repeated corticosteroid injection and this has led to the development of other alternatives for injection. As mentioned above these injections have an anti-inflammatory effect and it is by this action that pain is reduced. They do not propose to effect the joint structure itself, in contrast to other injection options such as Hyaluronic acid and Platelet-Rich-Plasma.
Hyaluronic acid injection, known commercially as Synvisc or Hyaluronan, aims to lubricate and protect the joint and reduce cartilage degeneration. Administration of these injection therapies also known as viscosupplementation, involves 3-5 repeated weekly injections, and is considerably more expensive than corticosteroid injection. Studies do show small improvements in pain and function with these injections, however national recommendation guidelines vary with some countries advocating for it’s use and some against.
PRP injections involve taking a sample of your own blood which is then spun through a centrifuge to separate the platelets and the plasma, which are then injected into the joint. PRP works by reducing inflammation and promoting healing within the cartilage through the action of a number of growth factors, which are highly concentrated in the PRP. There are increasing studies demonstrating that PRP injections may be superior to both corticosteroid and hyaluronic acid injection, with peak benefits varying from 3-6 months and lasting for up to 1 year, possibly due to the induced changes within the joint. Further studies have been done on multiple injections with some showing better improvements with 3 injections compared to one, although similar studies have not demonstrated this same result. Although the intervention is relatively new, evidence is mounting that PRP injections may be a good option for joint pain, whilst soft tissue PRP injection is more controversial at this point. Despite this mounting evidence PRP is still not a recommended treatment in international guidelines for the treatment of arthritis and it is not funded by Medicare or health funds in Australia, however it is a treatment option for those who are prepared to self-fund at a cost of $350 currently per injection.
Intra-articular injections show promise as symptomatic second-line management options for knee OA. However, additional research is necessary to further establish the long-term effectiveness, safety, and cost-effectiveness of these treatments. Healthcare providers should consider individual patient factors, preferences, and treatment goals when selecting the most appropriate injection therapy for knee OA. Shared decision-making between healthcare providers and patients is crucial to ensure the best possible outcomes and patient satisfaction.
References:
Belk JW, Kraeutler MJ, Houck DA, Goodrich JA, Dragoo JL, McCarty EC. Platelet-Rich Plasma Versus Hyaluronic Acid for Knee Osteoarthritis: A Systematic Review and Meta-analysis of Randomized Controlled Trials. The American Journal of Sports Medicine. 2021;49(1):249-260. doi:10.1177/0363546520909397
Filardo, G. et al, PRP Injections for the Treatment of Knee Osteoarthritis: A Meta-Analysis of Randomized Controlled Trials, Cartilage, 2021, Vol.13 (1_suppl), p.364S-375S
Gilat, Ret al. Hyaluronic acid and platelet-rich plasma for the management of knee osteoarthritis, International orthopaedics, 2021, Vol.45 (2), p.345-354
Uslu Guvendi E, Askin A, Guvendi G, Kocyigit H. Comparison of efficiency between corticosteroid and platelet rich plasma injection therapies in patients with knee osteoarthritis. Arch Rheumatology, 2018;33:273-281
Vilchez-Cavazos et al 2019, Comparison of the Clinical Effectiveness of Single Versus Multiple Injections of Platelet-Rich Plasma in the Treatment of Knee Osteoarthritis: A Systematic Review and Meta-analysis, The Orthopaedic Journal of Sports Medicine, 7
