Stem cell injections for osteoarthritis of the knee

Abstract

BACKGROUND: Stem cells are specialised precursor cells that can replace aged or damaged cells and thereby maintain healthy tissue function. Stem cell therapy is increasingly used as a treatment for knee osteoarthritis, despite the lack of clarity around the mechanism by which stem cell therapy may slow down disease progression in osteoarthritis, and uncertainty regarding its benefits and harms. OBJECTIVES: To assess the benefits and harms of stem cell injections for people with osteoarthritis of the knee. A secondary objective is to maintain the currency of the evidence, using a living systematic review approach. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and Embase on 15 September 2023, unrestricted by date or language of publication. We also searched ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform (ICTRP) for relevant trial protocols and ongoing trials. SELECTION CRITERIA: We included randomised controlled trials (RCTs), or trials using quasi-randomised methods of participant allocation, comparing stem cell injection with placebo injection, no treatment or usual care, glucocorticoid injection, other injections, exercise, drug therapy, surgical interventions, and supplements and complementary therapies in people with knee osteoarthritis. DATA COLLECTION AND ANALYSIS: Two review authors selected studies for inclusion, extracted trial characteristics and outcome data, assessed risk of bias and assessed the certainty of evidence using the GRADE approach. The primary comparison was stem cell injection compared with placebo injection. The primary time point for pain, function and quality of life was three to six months, and the end of the trial period for participant-reported success, joint structure changes and adverse event outcomes. Major outcomes were pain, function, quality of life, global assessment of success, radiographic joint progression, withdrawals due to adverse events and serious adverse events. MAIN RESULTS: = 0%; 7 trials, 461 participants) and there were no reported withdrawals due to adverse events. We downgraded the evidence to very low certainty due to indirectness, suspected publication bias and imprecision. Radiographic progression was not assessed in any of the included studies. AUTHORS' CONCLUSIONS: Compared with placebo injections and based upon low-certainty evidence, stem cell injections for people with knee osteoarthritis may slightly improve pain and function. We are uncertain of the effects of stem cell injections on quality of life or the number who report treatment success. Although the putative benefits of stem cell therapies for osteoarthritis include potential regenerative effects on damaged tissues, particularly articular cartilage, we remain uncertain of the effect of stem cell injections on structural progression in the knee (measured by radiographic appearance). There is also uncertainty regarding the safety of stem cell injections. Serious adverse events were infrequently reported, although all invasive joint procedures (including injections) carry a small risk of septic arthritis. The risk of other important harms, including potential concerns related to the use of a therapy with the theoretical capacity to promote cell growth, or to the use of allogeneic cells, remains unknown.

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