Cell-Based Treatments for Knee Osteoarthritis: What the Evidence Shows

Cell-based treatments for knee osteoarthritis include injections of bone marrow aspirate concentrate or fat-derived products containing mesenchymal cells. They are often presented as “stem-cell therapy”.

What does the evidence show?

• Some meta-analyses report improvements in pain and function, but studies are small, heterogeneous and often lack adequate control groups [1, 2]
• There is no reliable evidence that these injections regrow cartilage
• The American College of Rheumatology guideline strongly recommends against stem-cell injections for knee osteoarthritis, citing heterogeneity and lack of standardisation [3]

Further reading: the guide “Knee Osteoarthritis” and the articles PRP (Platelet-Rich Plasma) Therapy: What the Evidence Shows and Hyaluronic Acid Injections for Knee Osteoarthritis.

Things to consider

• Preparation methods vary widely and are not standardised
• Costs are often high
• Regulation differs between countries

Who may consider it?

These treatments are not recommended as routine care. Exercise, weight management and other first-line treatments remain the basis. Patients considering such options should discuss the evidence and risks carefully with their physician, ideally within a research setting.

Knee osteoarthritis in brief

Knee osteoarthritis is a condition of the whole joint, not just “wear and tear” of cartilage. The cartilage (the smooth layer covering the bone ends) becomes thinner, the bone beneath it changes, small bony outgrowths (osteophytes) form and the joint lining can become inflamed. Typical symptoms are pain on walking or climbing stairs, stiffness after rest, swelling and reduced confidence in the knee. Symptoms often fluctuate, with good and bad periods, and the severity on X-ray does not always match the level of pain.

What “cell-based” treatment means

The term is used for injections prepared from a patient’s own tissues, most often bone marrow aspirate concentrate (cells taken from the pelvic bone) or preparations from fat tissue. These products are often described as “stem cell” treatments, although they contain a mixture of cells and only a small proportion are true stem cells (cells able to develop into other cell types). Their proposed effect is mainly to modify inflammation rather than to rebuild cartilage. Preparation methods, cell numbers and protocols differ greatly between centres, which makes results hard to compare.

Treatments with stronger evidence

For most people with knee osteoarthritis, the foundation of care is:

• Exercise therapy: strengthening of the thigh and hip muscles and aerobic activity such as walking or cycling.
• Weight management where relevant, because each kilogram lost reduces load on the knee.
• Education and self-management: understanding the condition, pacing activities and staying active.
• Pain relief with medication when needed, used for the shortest effective time.
• Walking aids, insoles or braces in selected cases.
• Injections such as corticosteroids for short-term relief of flare-ups, after individual assessment.
• Joint replacement surgery for advanced disease when pain and function remain poor despite other measures.

The exercise programme is planned by your physical medicine and rehabilitation specialist and the physiotherapist and progressed gradually.

Questions to ask before considering a cell-based injection

• What exactly will be injected, and how is it prepared?
• What is the evidence for my stage of osteoarthritis?
• What are the risks, including those from tissue harvesting?
• Is the treatment offered within a registered study or approved framework in my country?
• What is the total cost, and what is the plan if there is no improvement?

What you can do at home

• Stay active every day; movement nourishes cartilage and maintains muscle strength.
• Do your strengthening exercises regularly; benefits usually build over 6–12 weeks.
• Use a cane on the opposite side during painful periods if advised.
• Choose cushioned, supportive footwear.
• Use heat or cold for short periods to ease pain and stiffness.

When to consult your PM&R specialist

Seek review if knee pain limits walking or sleep, if the knee swells repeatedly or gives way, or before deciding on any injection treatment. A physical medicine and rehabilitation (PM&R) specialist can assess the knee, explain the evidence for each option and guide therapy and support treatments.

Frequently asked questions

Do stem cells regrow cartilage? This has not been shown reliably in humans.

Are there risks? Procedure-related pain, swelling and, rarely, infection. See Knee osteoarthritis treatment without surgery.

Is a cell-based injection an alternative to knee replacement? There is no reliable evidence that it can replace surgery in advanced osteoarthritis. The decision about surgery depends on symptoms, function and examination.

Will exercise damage my knee further? No. Appropriately dosed exercise is one of the most effective treatments for knee osteoarthritis and does not accelerate joint damage.

Assessment and contact

You can request an appointment or a second-opinion review of existing reports and imaging: Contact & second opinion (WhatsApp). This page is general health information. Diagnosis and treatment decisions are made individually after examination.

Sources

1. Cao M, et al. Efficacy and safety of mesenchymal stem cells in knee osteoarthritis: a systematic review and meta-analysis of randomized controlled trials. Stem Cell Res Ther. 2025. PMID: 40055739
2. Keeling LE, et al. Bone Marrow Aspirate Concentrate for the Treatment of Knee Osteoarthritis: A Systematic Review. Am J Sports Med. 2022. PMID: 34236913
3. Kolasinski SL, et al. 2019 American College of Rheumatology/Arthritis Foundation Guideline for the Management of Osteoarthritis of the Hand, Hip, and Knee. Arthritis Rheumatol. 2020. PMID: 31908163