A plain-language look at what the evidence really shows about PRP, “stem cell,” and other regenerative injections for knee and hip arthritis — based on the 2026 American Association of Hip & Knee Surgeons (AAHKS) position statement on orthobiologics.
The Decision Many Patients Face
When knee or hip arthritis starts limiting daily life, it is completely natural to look for anything that might avoid or delay an operation. That instinct is reasonable — and exploring genuine alternatives first is exactly the right thing to do. The difficulty is that the internet, and some clinics, now offer a growing menu of injections promising to “regrow cartilage,” “heal the joint naturally,” or “avoid a knee replacement,” often for a large cash fee.
- You want to postpone or avoid surgery — and you deserve to know which alternatives are real.
- You’re told an injection can “regenerate” your joint — but is that actually true?
- It isn’t covered by insurance and can cost a great deal out of your own pocket.
- It’s genuinely hard to tell marketing from medicine when both sound confident.
Why the Marketing Can Mislead
- Much of the “evidence” promoted for these injections comes from small, industry- or provider-sponsored studies — not independent, high-quality trials.
- Online information often emphasises benefits while leaving out the risks, the costs, and the simpler alternatives that work.
- The label “stem cell” is routinely used for products that contain almost no stem cells at all.
Absolutely. I’d make the wording more active, direct, medically professional, and SEO-friendly, while keeping the evidence and terminology from your article unchanged.
What’s Actually Being Sold?
Several types of injections are marketed for knee and hip arthritis. Here’s what each treatment involves and what the evidence actually shows.
PRP
Platelet-Rich Plasma
What it is: A doctor draws a small amount of your blood and spins it in a machine to concentrate the platelets. The doctor then injects the concentrated plasma into the joint.
The evidence: In advanced knee arthritis, good-quality trials found no meaningful benefit compared with a saline injection, steroid injection, or gel injection.
BMAC
“Stem Cell” Injection
What it is: A doctor draws bone marrow from your pelvis, processes it to concentrate the cells, and injects the preparation into the joint. Clinics often market BMAC as a “stem cell” treatment.
The catch: Commercial BMAC preparations contain less than 0.01% actual stem cells. Therefore, calling BMAC a true “stem cell” treatment can be misleading.
“Stem Cells” / MSCs
From Fat or Lab-Grown Cells
What it is: Clinics obtain these cells from fat or bone marrow. Some providers also grow the cells in a laboratory before injecting them and market the treatment as a regenerative therapy.
The evidence: Studies show, at best, a mild benefit over placebo. Moreover, these treatments have not performed better than a simple steroid injection for advanced knee arthritis.
Viscosupplementation
Hyaluronic Acid “Gel”
What it is: A doctor injects hyaluronic acid, a lubricating gel, into the joint to help cushion it. Although it is not a biologic treatment, clinics often market it alongside PRP and other regenerative injections.
The evidence: Patients with advanced arthritis may experience only a small and inconsistent benefit. Consequently, several clinical guidelines no longer routinely recommend hyaluronic acid injections.
The “Stem Cell” Reality
<0.01%
Commercial BMAC preparations contain less than 0.01% mesenchymal stem cells. That represents an extremely small concentration and does not provide evidence that the injection can regenerate lost cartilage.
In simple terms, fewer than 1 in every 10,000 cells are mesenchymal stem cells. Therefore, patients should carefully question claims that BMAC injections can “regrow” damaged cartilage.
A Few Numbers Worth Knowing
Not All Cartilage Damage Is the Same
This is the single most useful idea to take away: whether anything can “repair” cartilage depends entirely on what kind of damage you have.
Focal Cartilage Defect
A localised “pothole” · often younger, after injury
Arthroscopy: the crater is the defect; surrounding cartilage is intact.
- The cartilage around it is still healthy.
- Genuine repair options exist — e.g. OATS (transplanting a small plug of your own cartilage-and-bone) or MACI (growing your own cartilage cells and re-implanting them).
- These are established, evidence-based procedures — for the right patient.
Advanced (Age-Related) Osteoarthritis
The arthritis affects the entire joint, often resulting in bone-on-bone contact.
X-ray: The joint space becomes narrow, and bone spurs (osteophytes) develop.
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Advanced osteoarthritis destroys cartilage throughout the joint, leaving no localised area for doctors to repair or patch.
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No injection or “stem cell” product can currently regrow an entire compartment of lost cartilage.
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Instead, doctors focus on managing symptoms and maintaining function. When arthritis significantly affects quality of life, joint replacement can provide a reliable treatment option for the right patient.
What Genuinely Helps Arthritis
- Staying active, with targeted physiotherapy and muscle strengthening.
- Weight management — every kilogram lost meaningfully reduces load on the joint.
- Simple pain relief, and for occasional flares, a well-timed steroid injection.
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When advanced arthritis starts affecting your quality of life, modern hip knee replacement offers one of the most reliably successful treatments in medicine. However, an orthopaedic surgeon recommends joint replacement only when it suits the patient’s symptoms, health, and stage of arthritis — not simply because arthritis appears on an X-ray.
Choosing the Right Arthritis Treatment
Importantly, cartilage damage varies from patient to patient, so doctors choose treatment based on the type and stage of arthritis. For example, carefully selected patients with localised cartilage defects may benefit from specific cartilage-repair procedures. In contrast, advanced age-related osteoarthritis destroys cartilage across the joint, and current injections or “stem cell” products cannot regrow the lost cartilage. In addition, targeted physiotherapy, muscle strengthening, weight management, appropriate pain relief, and selected steroid injections can help patients manage arthritis symptoms and maintain mobility. Ultimately, when severe knee or hip arthritis limits daily activities and affects quality of life, an orthopaedic surgeon may recommend joint replacement after considering the patient’s symptoms, X-rays, activity level, and overall health.
