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.
What’s Actually Being Sold?
The injections most commonly marketed for arthritis — explained in plain terms.
PRP
What it is: your own blood is drawn and spun in a machine to concentrate the platelets, then injected into the joint.
BMAC
What it is: marrow is drawn from your pelvis, spun down, and injected. Sold as a “stem cell” therapy.
“Stem Cells” / MSCs
What it is: cells taken from fat or marrow, sometimes grown in a lab, marketed as “regenerative.”
Viscosupplementation
What it is: a lubricating gel injected to “cushion” the joint. Not a biologic, but often sold alongside them.
In plain terms: fewer than 1 in every 10,000 cells.
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
Worn across the whole joint · bone-on-bone
X-ray: narrowed joint space + bone spurs (osteophytes).
- The cartilage is gone across the joint — there is nothing localised left to patch.
- No injection or “stem cell” product can regrow a whole compartment of cartilage.
- The honest options are to manage it well, or — when quality of life demands — joint replacement.
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.
- When arthritis is advanced and quality of life is affected, modern hip/knee replacement is one of the most reliably successful operations in medicine — but it is a decision for the right patient at the right time, not for everyone.
