Objective: To synthesize up-to-date evidence on the efficacy, safety and practical use of platelet-rich plasma (PRP) and bone marrow–derived biologic therapies, including bone marrow aspirate concentrate (BMAC) and mesenchymal stem cells (MSCs), in knee osteoarthritis (KOA).
Methods: Clinical practice guidelines, randomized controlled trials and meta-analyses up to October 2025 were searched, prioritizing studies that compared these interventions with placebo or active intra-articular comparators. Data were synthesized narratively and contrasted with current guideline recommendations. Primary outcomes included pain, function, durability of effect and safety.
Results: Most contemporary international guidelines do not recommend PRP or intra-articular “stem cell” injections for KOA because of inconsistent results and low-certainty evidence, although some allow PRP to be considered in selected contexts. Meta-analyses show that PRP improves pain and function compared with placebo or hyaluronic acid. Several trials and meta-analyses suggest modest benefits of BMAC and MSCs on pain and function, but these findings are limited by small sample sizes, heterogeneous preparation protocols and the possibility of substantial placebo/contextual effects. Serious adverse events are rare.
Conclusions: PRP may be considered for patients with mild-to-moderate KOA who remain symptomatic despite optimized core conservative care, provided that patients are clearly informed about its off-label status and protocol variability. At present, intra-articular use of BMAC and MSCs should preferably be restricted to research settings or registry-based programs, alongside efforts to standardize preparation, dosing and reporting.