“Stem cells for the knee” is one of the most frequent searches in regenerative medicine. That is no surprise: osteoarthritis (cartilage wear) is a leading cause of pain and limitation in adults, and many people look for alternatives before considering knee replacement surgery.
How are they applied?
In most studies, mesenchymal stem cells — obtained from fat, bone marrow or umbilical cord — are given as an injection into the joint (intra-articular), performed by a specialist physician.
The idea is not to “build a new knee”, but to take advantage of their anti-inflammatory effect and their ability to send signals that support tissue repair.
What did the 2025 studies find?
Two systematic reviews published in 2025 analyzed the available randomized clinical trials:
- One pooled 11 trials with 811 patients and found that stem cells are associated with less pain, with more modest improvements in knee function.
- Another, published in Frontiers in Medicine (8 trials, 467 patients), focused on the contextual effect: the part of the improvement due to factors such as expectations, medical attention or the procedure itself. It found that at 6 months about 63% of the pain improvement is explained by those factors, and that the cells add a modest additional benefit.
How should these results be read?
- Treated patients do improve, especially in pain.
- A large part of that improvement also appears in comparison groups, so the benefit from the cells themselves is smaller than is sometimes advertised.
- The certainty of the evidence is still considered low: larger studies with longer follow-up and well-characterized products are needed.
Questions worth asking your doctor
- What type of cell will be used and where does it come from?
- Which laboratory makes it and what health registration does it have?
- What results are reasonable to expect in my case, and how soon?
- Which other treatments (exercise, weight control, physical therapy) should be combined?
Regenerative medicine is moving fast, and the best way to benefit from it is with clear information and realistic expectations.
- Yin et al. Contextual effects of mesenchymal stem cell injections for knee osteoarthritis: systematic review and meta-analysis of randomized controlled trials. Frontiers in Medicine, 2025. doi:10.3389/fmed.2025.1636181
- Mesenchymal stem cell-based therapy for osteoarthritis: a systematic review and meta-analysis of clinical outcomes and functional recovery. 2025. PMC12816338
This content is for informational purposes only and does not replace evaluation by a health professional. It has not been evaluated by the FDA.
