Table 1.

Subject characteristics at baseline visit

Variable	Statistic (N=120)
Age (years), mean (SD)	62.3 (10.3)
Females, frequency (%)	62 (51.7)
Number of days to follow-up appointment, median (IQR)	8.0 (7.0 to 13.5)
KOOS pain subscale score (0–100)*, median (IQR)	44.4 (36.1 to 55.6)
Pain on nominated activity VAS (0–10)†, median (IQR)	7.0 (5.5 to 7.7)‡
Pain in last week VAS (0–10)†, median (IQR)	6.5 (4.7 to 7.8)‡
Maximal Kellgren–Lawrence grade in either patellofemoral or tibiofemoral compartment	–
Grade 2, frequency (%)	42 (38.5)§
Grade 3, frequency (%)	60 (55.1)§
Grade 4, frequency (%)	7 (6.4)§
Synovial tissue volume (mm3), median (IQR)	8177 (5743 to 13 056)¶
Synovial fluid volume (mm3), median (IQR)	8158 (5699 to 12 457)¶
Number of responders to injection, at follow-up visit, frequency (%)	85 (70.8)

*KOOS pain subscale is scored from 100 (no pain) to 0 (extreme pain).

†VASs are scored from 0 (no pain) to 10 (pain as bad as you can imagine).

‡Five patients and three patients neglected to complete their pain on nominated activity VAS and pain in last week VAS, respectively.

§Kellgren–Lawrence data is available only for 115 patients in total; the remaining 12 were assessed for study eligibility via MRI or arthroscopy report.

¶Nine patients’ MRI images were of insufficient quality to allow volume calculation.

KOOS, Knee Injury and Osteoarthritis Outcome Score; VAS, Visual Analogue Scale.