Table 2. Study characteristics of the included studies.

HA: hyaluronic acid; HHS: Harris hip score; HMW: high molecular weight; Lp PRP: leukocyte poor PRP; LMW: low molecular weight; Na: sodium; NR: not reported; OARSI: Osteoarthritis Research Society International; PRP: platelet-rich plasma; RCT: randomized controlled trial; VAS: visual analog scale; WOMAC: Western Ontario and McMaster Universities Arthritis Index

Authors	Country	Study design	Number of participants	Average age (years)	Intervention	Duration	Outcomes measured
Dallari et al. [21]	Italy	RCT	80 (PRP = 44, HA = 36)	NR	Autologous PRP (5 mL) versus HA (30 mg/2 mL)	12 months	Therapeutic efficacy of autologous PRP; therapeutic efficacy of HA
Di Sante et al. [22]	Italy	RCT	43 (PRP = 21, HA = 22)	PRP = 71.37±6.03, HA = 73.62±7.87	Na-HA (30 mg/2 mL) versus PRP (3 mL)	16 weeks	Pain reduction was measured by VAS; pain reduction was measured by WOMAC pain scale
Kraeutler et al. [24]	USA	Double-blind, randomized pilot study	31 (PRP = 18, HA = 13)	PRP = 53.3±8.4, HA = 53.6±7.6	Lp PRP (1-2 mL) versus LMW HA (2.5 mL)	12 weeks	Efficacy of intra-articular injection of Lp PRP; efficacy of intra-articular injections of LMW HA
Villanova-López et al. [26]	Spain	Phase III double-blinded, controlled trial	74 (PRP = 38, HA = 36)	PRP = 61.2±9.72, HA = 61.1±12.3	PRP (6 mL) versus HA (60 mg/6 mL)	12 months	Pain was assessed using VAS score; HHS score was used as functional score; WOMAC score was used as functional score; analgesia, adverse events, cellular components in peripheral blood, cellular components in PRP, and clinical response were assessed using OARSI criteria
Nouri et al. [25]	Iran	RCT with three parallel groups	70 (PRP = 35, HA = 35)	PRP = 58.22±5.10, HA = 60.93±4.54	PRP 5 mL versus HMW HA 50 mg/2.5 mL	Two injections within two weeks' interval	VAS; WOMAC; Lequesne questionnaire
Doria et al. [23]	Italy	Prospective double-blinded RCT	80 (PRP = 40, HA = 40)	PRP = 67.3±5.8, HA = 68±4.6	PRP 5 mL versus HA (15 mg/mL)	12 weeks	VAS; WOMAC
Battaglia et al. [20]	Italy	RCT	100 (PRP = 50, HA = 50)	PRP = 51±12, HA = 56±12	Autologous PRP (5 mL) versus HMW HA (30 mg/2 mL)	12 months	HHS; VAS