Injections in the Knee for Osteoarthritis
by Jill Blacksten, OMSII
Osteoarthritis is a degenerative disease that occurs when protective cartilage on the end of bones begins to wear down. The most common form of arthritis, osteoarthritis, generally affects joints such as knees. When treating osteoarthritis in knees, injections can be used to relieve pain and decrease inflammation. It is common practice to receive knee injections prior to having a knee replacement. Using knee injections, rather than oral medications, provides treatment directly to the knee which can lead to immediate relief within the joint.
There are three common types of substances given by intra-articular Injection:
- Hyaluronic Acid (HA)
- Platelet-rich plasma (PRP)
Corticosteroid injections are commonly used in clinical practice to treat knee pain. By mimicking cortisol, a hormone naturally found in the body, corticosteroids help decrease inflammation. These injections are used to provide short-term pain relief through anti-inflammatory properties and suppression of the immune system. This decrease in inflammation and pain can lead to improvements in mobility and function. On the other hand, using corticosteroid injections can damage cartilage and weaken the knee.
In 2017, a study compared patients with intra-articular triamcinolone injections (a corticosteroid) to saline (the control). Magnetic Resonance Imaging (MRI) scans were done at 0, 12, and 24 months. Patients received injections of intra-articular triamcinolone or saline every 12 weeks for 2 years. After 2 years, no significant difference in knee pain was found in the corticosteroid group vs the saline group. Also, the MRI scans showed that cartilage loss was significantly greater in patients who received triamcinolone injections (2).
Hyaluronic acid injections (viscosupplementation) are another type of injection used to treat osteoarthritis. This sugary substance naturally occurs in the synovial fluid of joints and lubricates these joints. As osteoarthritis worsens, the amount of hyaluronic acid within joints decreases. By increasing the amount of hyaluronic acid through supplemental injections, mobility may improve and pain may decrease.
Platelet Rich Plasma is another type of injection made from the patient’s plasma or derived from a commercial product. This plasma contains varying amounts of white blood cells and platelets which are used to stimulate healing of cartilage in joints. These platelets have natural healing properties and can increase function and decrease pain in knees.
There was no difference in outcomes between patients who received PRP vs. patients who received hyaluronic acid. However, patients who received PRP were less likely to need surgical intervention after two years (1).
When PRP injections were compared to intra-articular injections of steroids, hyaluronic acid, ozone, and dextrose injections, PRP injections demonstrated better function, less pain, and higher quality of life. The benefits of PRP injections became clinically significant after 6 months and up to 12 months after treatment (3).Knee injections may be desirable for some individuals. These injections can be helpful for people who want a quick, though short-lived, relief of pain. This may include individuals delaying surgery, those who want to enjoy a vacation, or those who want to try “conservative” treatments.When considering knee injections, it is important to note that these injections should be avoided prior to knee replacement since there can be an increase in the rate of infection with surgery. In a study with 36,000 patients, patients who received a knee injection had an increased infection rate at both 3 months and 6 months after surgery (4).
Instead of injections into the knee, physical therapy may be a better option. Physical therapy can help strengthen the muscles around the joint which can relieve symptoms. According to a study by Deyel et. al., physical therapy led to better outcomes after a year when compared to patients who received intra-articular corticosteroids. Patients who participated in physical therapy could attend up to 11 physical therapy sessions while patients who received intra-articular steroids could receive up to 3 injections. After one year, patients who received physical therapy had better physical function and less pain than patients who received corticosteroid injections (5).
In regards to intra-articular injections, it is clear that more research needs to be done to compare the different types of injections. Studies provide conflicting evidence making it difficult to determine which treatment is most beneficial. Physical therapy may be an alternative to injections since physical therapy has been shown to improve function and decrease pain. In short, intra-articular injections will not cure osteoarthritis though pain may be relieved temporarily. When treating osteoarthritis, is important to discuss all options with your doctor.
- Di Martino A, Di Matteo B, Papio T, Tentoni F, Selleri F, Cenacchi A, Kon E, Filardo G. Platelet-rich plasma versus hyaluronic acid injections for the treatment of knee osteoarthritis: results at 5 years of a double-blind, randomized controlled trial. Am J Sports Med. 2019 Feb;47(2):347-54. Epub 2018 Dec 13.
- McAlindon TE, LaValley MP, Harvey WF, Price LL, Driban JB, Zhang M, Ward RJ. Effect of Intra-articular Triamcinolone vs Saline on Knee Cartilage Volume and Pain in Patients With Knee Osteoarthritis: A Randomized Clinical Trial. JAMA. 2017 May 16;317(19):1967-1975. doi: 10.1001/jama.2017.5283.
- Filardo, G., Previtali, D., Napoli, F., Candrian, C., Zaffagnini, S., & Grassi, A. (2020). PRP Injections for the Treatment of Knee Osteoarthritis: A Meta-Analysis of Randomized Controlled Trials. Cartilage, 1-12. https://doi.org/10.1177/1947603520931170
- Cancienne JM, Werner BC, Luetkemeyer LM, Browne JA. Does Timing of Previous Intra-Articular Steroid Injection Affect the Post-Operative Rate of Infection in Total Knee Arthroplasty? J Arthroplasty. 2015 Nov;30(11):1879-82. doi: 10.1016/j.arth.2015.05.027. Epub 2015 May 23.
- Deyle GD, Allen CS, Allison SC, Gill NW, Hando BR, Petersen EJ, Dusenberry DI, Rhon DI. Physical Therapy versus Glucocorticoid Injection for Osteoarthritis of the Knee. N Engl J Med. 2020 Apr 9;382(15):1420-1429. doi: 10.1056/NEJMoa1905877. PMID: 32268027.