Table 1. Summary of main findings of the included clinical studies.

WBCs: white blood cells; IL-1β: interleukin-1β; IL-1RA: interleukin-1 receptor antagonist; WOMAC: Western Ontario and McMaster Universities Arthritis Index; APS: autologous protein solution; OMERACT-OARSI: Outcomes Measures in Rheumatology-Osteoarthritis Research Society International; IA: intra-articular; CGI-S/C: Clinical Global Impression of severity/change; KOOS: knee injury and osteoarthritis outcome score; NPRS: numeric pain rating scale; MRI: magnetic resonance imaging; KL: Kellgren-Lawrence.

Author [Reference]	Main Findings
King et al. [7]	This study demonstrated a positive correlation between the concentration of WBCs and ratio of anti-inflammatory IL-1RA to pro-inflammatory IL-1β in the APS formulation and the WOMAC pain score. Additionally, 85.7% of the subjects whose IL-1RA to IL-1β ratio was greater than 1,000 or a WBC count >30,000/µl were OMERACT-OARSI responders at six months' follow-up.
Drumpt et al. [8]	Administration of IA APS is safe and led to significant improvement in all WOMAC subscales and attainment of OMERACT-OARSI high pain responder status at 18 months ' follow-up.
Kon et al. [9]	Administration of IA APS is safe and led to significant improvement in WOMAC, SF-36 bodily pain subscale, SF-36 role emotional health subscale, and CGI-S/C scores compared to the saline group at 12 months' follow-up.
Kon et al. [10]	Administration of IA APS is safe and led to significant improvement in VAS, all KOOS and WOMAC subscales, and SF-36 physical component compared to the baseline at 36 months' follow-up. The number of responders also increased from seven at 12 months' follow-up to nine at 24 and 36 months' follow-up.
Genechten et al. [11]	Administration of IA APS led to significant improvement in NPRS, KOOS, and Kujala scores at 12 months' follow-up. Additionally, MRI analysis showed significant improvement in KOOS symptoms and ADL subscales, and Kujala score in patients with major synovitis compared to patients with non-synovitis at 12 months' follow-up. Additionally, an overall responder rate of 53.7% was observed.
Kuwasawa et al. [12]	Administration of IA APS is safe and led to significant improvement in KOOS subscales compared to the baseline at 12 months' follow-up. The subgroup analysis showed that improvement in severe grades, that is, grade IV (on KL grade), was inferior to mild-to-moderate grades (grade II or III). The improvement in KOOS for KL grade II was significantly higher than in KL grade IV at 12 months' follow-up.