A systematic review of methodological heterogeneity and outcome discordance in PRP and MSC therapies for knee osteoarthritis
BMC Musculoskeletal Disorders · 9 Oct 2026
† Impact is the editorial-priority score. All scores are out of 100. Clinical is a stored clinical-importance score from the earlier method; it has not been recalculated.
Why it matters
Patients often ask about 'regenerative' knee injections, and this review supports counselling that any benefit appears symptomatic rather than cartilage-restoring, with low certainty.
The evidence
This systematic review pooled 17 studies (10 clinical, 7 lab, survey, or contextual) on platelet-rich plasma (PRP) and mesenchymal stem cell (MSC) injections for knee osteoarthritis, without a meta-analysis. Patient-reported pain and function scores (WOMAC, VAS) generally improved from baseline, but MRI (T2 mapping, WORMS, cartilage thickness) did not consistently show cartilage regrowth. GRADE certainty was low for symptom improvement (9 studies, about 1214 patients) and very low for structural regeneration (4 studies, 99 patients), and only 3 of 10 clinical studies classified their biologic product with a standardised system.
A coherent primary effect estimate is unavailable. Clinical relevance does not estimate treatment benefit.
Why this rigour score?
Meta-analysis (mixed designs)Design starting point: 42.6
Raised the score
- Prospectively registered+5.1
- Comprehensive literature search+3.4
Lowered the score
- No assessment of publication bias across 17 studies−6.8
- Pools mixed study designs−3.4
Methods at a glance
Recorded assessment- Comprehensive literature searchMet
- Risk of bias assessedMet
- Bias considered in synthesisMet
- Publication bias assessedNot met
- Study exclusions justifiedMet
- Prospective registrationMet
Not reported does not mean not done. Checks have different weights; this is not a count of boxes ticked.
See the full score breakdown
- Study design starting point
- 42.6
- Prospectively registered
- +5.1
- Pools mixed study designs
- −3.4
- Comprehensive literature search
- +3.4
- Risk of bias assessed in the included studies
- +3.4
- Risk of bias carried into the synthesis
- +2.5
- Excluded studies listed and justified
- +1.7
- No assessment of publication bias across 17 studies
- −6.8
- Final rigour score rounded
- 49 / 100
Study design sets the starting point and a ceiling of 82. Recorded methods then adjust the score. Points are shown to one decimal place; the final score uses unrounded values.
Checklist from the stored appraisal. “Not met” describes the recorded criterion; it does not always produce a deduction. This overview supports reading the full study.
For journal club
1.How would you counsel a 55-year-old with KL grade II knee OA who asks whether a PRP or stem cell injection will regrow cartilage and delay knee replacement?
2.Given costs of USD 500 to 2500 for PRP and up to USD 25000 for MSC therapy, which patients, if any, would you offer these injections to over hyaluronic acid or corticosteroid, and what follow-up would you plan?
Original publication title
A systematic review of methodological heterogeneity and outcome discordance in PRP and MSC therapies for knee osteoarthritis