Table 3.

Subgroup analyses of PRP compared with HA for WOMAC total scores at 12 months

Subgroup	No. of trials	Standard mean difference (95% CI)	P value	I2 (%)	Test of interaction, P
Total	8	− 1.47 (− 2.23, − 0.70)	0.000	95.3
Number of PRP injections
1	4	− 1.15 (− 2.14, − 0.85)	0.000	69.3	0.006
≥2	4	− 1.68 (− 2.35, − 0.72)	0.000	98.2
PRP spinning approach
Single	3	− 1.13 (− 2.22, − 0.85)	0.000	0.0	0.028
Double	5	− 1.62 (− 2.34, − 1.11)	0.000	88.4
PRP classification
LPP	3	− 2.89 (− 6.55, − 0.68)	0.000	82.4	0.002
LRP	5	0.86 (0.15, 1.56)	0.000	83.5
Fresh or frozen PRP
Fresh	5	0.78 (0.54,1.01)	0.000	57.8	0.105
Frozen	3	0.50 (0.33,0.67)	0.000	88.1
Activator used
Yes	4	− 2.78 (− 4.32, − 1.15)		82.1	0.031
No	4	0.58 (0.12, 1.58)		93.4
Risk of bias
Low	6	− 1.23 (− 2.08, − 0.35)	0.002	85.9	0.254
Unclear/high	2	− 1.33 (− 2.24, − 0.46)	0.004	89.4
Molecular weight
High	4	− 1.90 (− 4.53, 0.73)	0.157	97.9	0.003
Low	4	− 1.31 (− 1.97, − 0.64)	0.000	92.2
Structure
Cross-linked	4	− 2.06 (− 3.20, − 0.92)	0.352	96.2	0.000
Not cross-linked or unclear	4	− 0.57 (− 1.78, 0.63)	0.000	95.0