PRP and stem cell therapy get lumped together constantly in knee arthritis conversations, “regenerative injections,” “biologics,” sometimes even used interchangeably in marketing. They’re genuinely different products with different evidence bases, and conflating them does a disservice to patients trying to make an informed choice. This guide breaks down the real differences.
Product Differences
This is the foundational distinction, and it’s worth understanding clearly before anything else.
| Feature | PRP (Platelet-Rich Plasma) | MSC (Mesenchymal Stem Cell) Therapy |
| What it is | Your own blood, processed to concentrate platelets | Cells (from bone marrow, fat, or umbilical cord tissue) with regenerative/signalling properties |
| Contains living stem cells? | No | Yes |
| Source | Always autologous (your own blood) | Can be autologous or allogeneic (donor-derived) |
| Preparation | Same-day, simple centrifuge processing | Ranges from same-day concentration to weeks of laboratory culture and expansion |
| Primary proposed mechanism | Growth factors released from platelets supporting healing and reducing inflammation | Immunomodulation, anti-inflammatory signalling, and tissue repair support |
| Typical cost relative to the other | Generally lower | Generally higher, particularly for culture-expanded cell products |
PRP is essentially a concentration of your blood’s own healing factors. Stem cell therapy involves actual living cells with broader, more complex proposed biological actions. They are not simply different brand names for the same thing.
Evidence by Indication
Neither product has uniformly strong or weak evidence, it varies by what specifically you’re comparing and which outcome you’re measuring.
PRP for knee osteoarthritis:
- A growing number of randomised controlled trials have compared PRP to hyaluronic acid or placebo, with several showing modest pain and function improvement
- Evidence is generally considered more mature than stem cell therapy for this specific use, with more and larger controlled trials published
- Results still vary by preparation method, since “PRP” itself isn’t fully standardised across different devices and protocols
MSC therapy for knee osteoarthritis:
- Several small, controlled trials report pain and function improvement, with some imaging studies showing cartilage quality changes in a subset of patients
- Larger, better-controlled trials have generally shown more modest and inconsistent results than early studies suggested
- A notable US comparative trial (MILES) found bone marrow concentrate didn’t show a clear advantage over corticosteroid injection at one year
The honest summary: PRP currently has a somewhat larger and more mature body of controlled trial evidence specifically for knee OA, while MSC therapy’s evidence base, though growing, remains earlier-stage and more variable by cell source and protocol.
Protocol Differences
Beyond the product itself, how each is actually administered varies and affects both cost and practicality.
| Factor | PRP | MSC Therapy |
| Collection | Blood draw, same visit | Bone marrow aspiration, fat harvest, or no harvest if using donor-derived cells |
| Processing time | Minutes (centrifuge) | Same-day to several weeks, depending on whether cells are cultured |
| Typical number of sessions | Often 1-3 sessions | Varies widely; single or multiple sessions depending on protocol |
| Procedural invasiveness | Low (blood draw plus injection) | Variable; bone marrow aspiration is more invasive than a blood draw |
Risks
Both carry injection-related risks, but some specifics differ based on the collection and product type.
| Risk | PRP | MSC Therapy |
| Injection site pain/swelling | Common, usually temporary | Common, usually temporary |
| Infection risk | Low, standard injection risk | Low for intra-articular injection; bone marrow/fat harvest adds separate procedural risk |
| Allergic/immune reaction | Very low (autologous, your own blood) | Low for autologous; donor-derived (allogeneic) products carry additional, though generally low, immune consideration |
| Harvest-related discomfort | Minimal (blood draw) | Can be more significant for bone marrow aspiration or fat harvest, if autologous cells are used |
Neither option is risk-free, and neither has been linked to serious, common adverse events in regulated clinical settings, but the specific risk profile differs based on collection method and product source.
Questions Worth Asking When Comparing the Two
- What specific evidence exists for this exact product and preparation method, not “PRP” or “stem cells” as a general category?
- What’s the actual cell or platelet concentration being used, and how is that measured?
- How does the cost difference reflect genuine differences in evidence or just processing complexity?
- What administration route and number of sessions does this specific protocol involve?
- What would success actually look like, and how will it be measured?
Why There’s No Generic Winner
It would be convenient to simply declare one option definitively better, but that wouldn’t be honest. The right choice depends on:
- Your specific OA severity and goals – mild-to-moderate OA with modest goals might reasonably start with PRP, given its somewhat more mature, lower-cost evidence base
- What you’re hoping to achieve – if cartilage-level changes are the goal, neither option has strong, consistent evidence for this, and expectations should be calibrated accordingly
- Budget considerations – cost differences are real and worth weighing against the evidence strength for each option
- Individual response – patient response to either treatment varies, and population-level trial results don’t guarantee an individual outcome
A responsible recommendation weighs these factors against your specific situation, rather than defaulting to whichever product a particular clinic happens to offer or market most heavily.
Comparing at a Glance
| Consideration | PRP | MSC Therapy |
| Evidence maturity for knee OA | More established, larger trial base | Earlier-stage, growing but more variable |
| Typical cost | Lower | Higher |
| Invasiveness | Low | Variable, depends on source |
| Contains living cells | No | Yes |
| Best framed as | A moderately evidenced conservative option | An emerging option still being clarified by research |
How Marketing Sometimes Blurs This Distinction
It’s worth being aware that some clinic marketing deliberately uses vague terms like “regenerative injection” or “biologic therapy” without specifying whether PRP or stem cells are actually being offered, sometimes because the distinction affects both cost and what claims can reasonably be made. If you’re evaluating any clinic’s offering, ask directly and specifically: is this PRP, or does it contain actual stem cells, and from what source? A clinic that can’t or won’t answer this clearly is worth approaching with extra caution, regardless of how the treatment is marketed.
Frequently Asked Questions
Is stem cell therapy just a more advanced version of PRP?
No. They’re fundamentally different products, PRP is concentrated platelets from your blood, while stem cell therapy involves actual living cells with different proposed mechanisms.
Which has stronger evidence for knee osteoarthritis?
PRP currently has a somewhat larger, more mature body of controlled trial evidence for knee OA specifically, though both remain active areas of ongoing research.
Is PRP cheaper because it’s less effective?
Not necessarily. The cost difference largely reflects processing complexity (a simple blood draw versus cell harvesting and potential laboratory culture), not a direct measure of effectiveness.
Can PRP and stem cell therapy be combined?
Some protocols combine both, though combined approaches have their own, generally even more limited, evidence base specific to that combination.
Does either option regrow lost cartilage?
Neither has consistently, reliably demonstrated cartilage regrowth in controlled human trials. Some studies show modest imaging changes, but this isn’t an established outcome for either.
Which should I try first?
This depends on your OA severity, goals, and budget. A proper assessment reviewing your imaging and history is the right way to make this decision, not a generic recommendation.
Discuss Your Options With Our Team
If you’d like an honest comparison tailored to your specific knee and OA grade, request an assessment and bring any recent imaging. Learn more about knee osteoarthritis at 23C Regen.