Platelet-rich plasma (PRP) in osteoarthritis (OA) knee: Correct dose critical for long term clinical efficacy

Bansal H, Leon J, Pont JL, et al. · Scientific Reports

150 patients with knee osteoarthritis randomised 75 and 75 to a single injection of PRP standardised to 10 billion platelets or to 4 mL of hyaluronic acid, followed for one year. At 12 months the PRP group was ahead on WOMAC (51.94 plus or minus 7.35 versus 57.33 plus or minus 8.92, P < 0.001), on IKDC (62.8 plus or minus 6.24 versus 52.7 plus or minus 6.39, P < 0.001) and on six-minute pain-free walking distance (plus 120 metres versus plus 4, P < 0.001), while the hyaluronic acid group's early gains faded. The paper's stated purpose is standardising preparation: adding a 1 micrometre filtration step to a manual method raised platelet recovery to about 90 percent. The authors also report that falls in the pro-inflammatory cytokines IL-6 and TNF-alpha tracked WOMAC improvement at 3 months.

Population

Adults with moderate knee OA

Intervention

Single PRP injection with an absolute dose of 10 billion platelets

Comparator

Hyaluronic acid

Limitations

The comparator is hyaluronic acid, not saline, so this trial cannot separate the effect of PRP from the effect of an injection. Single centre, and the 10 billion platelet threshold is inferred from a comparison against a different substance rather than tested across randomised dose arms — no arm in this trial received a different platelet dose. No structural or imaging endpoint. A published author correction exists (PMID 34521970).