Table 2. Platelet-rich-plasma (PRP): Key studies showing compelling evidence of PRP’s effectiveness in knee osteoarthritis (KOA).

The table presents a compilation of critical studies that showcase the essential study designs and findings demonstrating PRP's efficacy in treating patients with KOA. These studies are clinical trials that have successfully met the criteria for inclusion in this review and carry a clinical evidence level of II or higher.

6-MWD, 6-Minute Walking Distance; BMAC, Bone Marrow Aspirate Concentrate; HA, Hyaluronic Acid; IKDC, International Knee Documentation Committee; JSW, Joint Space Width; KOOS, Knee Injury and Osteoarthritis Outcome Score; LEQ Index, Lequesne Algofunctional Index; mL, Milliliters; MRI, Magnetic Resonance Imaging; PRGF, Plasma Rich in Growth Factor; PRL, Prolotherapy; p, Probability; ROM, Range of Motion; TH, Triamcinolone Hexacetonide; VAS, Visual Analogue Scale; vs., Versus; WOMAC, Western Ontario and McMaster Universities Osteoarthritis Index.

Authors	Sample Size	Age (Years)	Dose/Platelet Concentration	PRP Type	Treatment Groups	Assessment Time	Assessment Tools	Findings
Raeissadat et al. (2021) [16]	200 patients	50-75	2 mL dose weekly for 3 weeks at 4-6x the whole blood	Non-activated and leukocyte-rich	HA (49) vs. PRP (52) vs. PRGF (51) vs. Ozone (48)	Baseline, 2, 6, and 12 months	WOMAC, VAS, and LEQ Index	PRP treatment led to lower VAS scores at six months when compared to ozone therapy, and at 12 months when compared to both hyaluronic acid (HA) and ozone therapy (p < 0.05). A similar significant decrease trend was observed with PRP in the WOMAC and LEQ indices as well (p < 0.05).
Bansal et al. (2021) [17]	132 patients	50 or older	Single 8 mL at 2.78-8.33x the whole blood (standardized to 10 billion platelets/8 mL injection)	Non-activated and leukocyte-poor	PRP (64) vs. HA (68)	Baseline, 1, 3, 6, and 12 months	WOMAC, IKDC, 6-MWD, JSW (via X-ray), and Articular cartilage thickness (via MRI)	PRP treatment resulted in reduced WOMAC scores across all time points (p < 0.05), increased IKDC scores from the three-month mark onwards (p < 0.05), and augmented 6-MWD (p < 0.05). PRP therapy was associated with decreased cartilage loss (p < 0.05). However, no significant differences were observed in JSW changes between the groups.
Dulic et al. (2021) [18]	175 patients	18 or older	Single injection at 7.23x the whole blood and leukocyte conc. at 2.22x the whole blood   (Dose unspecified)	Non-activated and leukocyte-rich	BMAC (111) vs. PRP (34) vs. HA (30)	Baseline, IKDC + WOMAC + KOOS (1, 3, 6, 9, and 12 months), VAS (3 days after, 7 days after, 14 days after, and 21 days after)	VAS, WOMAC, IKDC, and KOOS	PRP substantially alleviated knee pain, as shown by reduced VAS (p < 0.001) and WOMAC scores (p = 0,001) compared to baseline. PRP resulted in significant improvement in IKDC (p < 0.001) and KOOS scores (p < 0.01) compared to baseline. There was no significant difference in VAS scores between the HA and PRP groups. BMAC outperformed all groups across the parameters assessed.
Rahimzadeh et al. (2018) [19]	42 patients	40-70	7 mL dose monthly for 2 months at 5x the whole blood	Not stated	PRP (21) vs. PRL (21)	Baseline, 1 month, 2 months, and 6 months	WOMAC	PRP treatment significantly decreased WOMAC scores at two and six months compared to PRL (p = 0.004, p = 0.009, respectively).
Sdeek et al. (2021) [20]	189 patients	45-65	Unspecified dose at two-week interval for 6 weeks at 8.2x the whole blood	Non-activated and leukocyte-poor	PRP (95) vs. HA (94)	Baseline, 2, 6, 12, 18, 24, 30, and 36 months	WOMAC, IKDC, and VAS	PRP treatment showed significant improvement in WOMAC, IKDC, and VAS scores compared to baseline scores. However, no statistical comparison was conducted.
Wu et al. (2018) [21]	20 (40 knees) patients	50-75	Single injection of unstated concentration	Non-activated and leukocyte-rich	PRP (20) vs. Saline (20)	Baseline, 2 weeks, 1 month, 3 months, and 6 months	WOMAC, Knee Flexion and Extension Strength	PRP treatment significantly reduced WOMAC scores compared to the control (saline) group. The results were consistent across multiple follow-up assessments at two-week, one-month, three-month, and six-month intervals (p = 0.01, p = 0.05, p = 0.001, p = 0.05, respectively).
Nunes-Tamashiroet al. (2022) [22]	100 patients	40-85	Single injection at 4.61x whole blood	Non-activated (leukocytes not measured)	PRP (34) vs. TH (33) vs. Saline (33)	Baseline, 4 weeks, 8 weeks, 12 weeks, and 52 weeks	VAS, 6MWD, WOMAC, Quality of life, Time to up-and-go test, ROM Flexion/Extension, and Radiographic Assessment	Compared to the placebo (saline) group, patients in both PRP and TH groups experienced notably reduced VAS scores (p < 0.05), decreased WOMAC scores (p < 0.05), and improved outcomes in 6MWD (p < 0.05), time to complete the up-and-go test (p < 0.05), and ROM in flexion and extension (p < 0.05). Most noteworthy was that patients in the PRP group exhibited no statistically significant disease progression (p = 0.311) from baseline to the 52-week follow-up post-treatment compared to the placebo and TH groups.
Huang et al. (2019) [23]	120 patients	40-65	Single dose at 2x the whole blood	Non-activated and leukocyte-poor	PRP (40) vs. HA (40) vs. Corticosteroids (CS) (40)	Baseline, 3 months, 6 months, 9 months, and 12 months	WOMAC and VAS	PRP treatment decreased WOMAC compared to other groups (p < 0.05). PRP significantly decreased VAS compared to baseline at all time points (p < 0.05), but no intergroup analysis was done.