Background: Most studies use platelet-rich plasma (PRP) requiring multiple intraarticular injections for knee osteoarthritis (OA).
Objective: To investigate the efficacy of a single intraarticular PRP injection for patients with early knee OA and consider subgroup analyses of radiographic severity and age, respectively.
Methods: Forty-one patients with knee OA (Kellgren-Lawrence grade 1-2) received a single PRP injection into the target knee and were assessed at baseline and 1, 3, and 6 months postinjection. The primary outcome was the mean change from baseline in the visual analog scale (VAS) pain (0-100 mm) at 6 months postinjection. Secondary outcomes included the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Lequesne index, single leg stance test (SLS), use of rescue analgesics and patients' satisfaction.
Results: Thirty-eight patients completed the study. The mean pain VAS decreased significantly from 45.6 ± 13.0 mm at baseline to 16.9 ± 13.4 mm, 14.0 ± 13.1 mm and 15.5 ± 14.0 mm at 1, 3 and 6-month follow-ups (p< 0.001 for all). Significant improvements in WOMAC, Lequesne index, SLS and consumption of analgesics from baseline (p< 0.001 for all) were noted at each follow-up. Patients' satisfaction was high. No serious adverse events occurred. Subgroup analyses revealed that patients with grade 1 OA showed significantly greater VAS pain reduction at 3 months (p= 0.006) and 6 months (p= 0.005) than patients with grade 2 OA. The older-age group (age > 60) showed significantly greater improvements in VAS pain, WOMAC function subscale scores and total scores at 6-month postinjection, compared with the younger age-group (age ≤ 60). The younger-age group reported better satisfaction at 1 and 3-month postinjection.
Conclusions: One injection of PRP improved pain and function for 6 months for patients with early knee OA. This study supports putting the one-injection regimen into clinical practice. Further research is needed for more definite conclusions.
Keywords: Intraarticular injection; WOMAC score; knee osteoarthritis; pain; platelet-rich plasma.