Vina E, et al. – The specialists explored the involvement of race, sex and risk factors in radiographic worsening of knee osteoarthritis (KOA). Accumulated evidence showed that African–American (AA) males had a higher risk of medial joint space loss compared with White (WH) and AA females. Controlling for established risk factors attenuated the correlations between race/sex and disease worsening. Hence, the data indicated that risk factors such as obesity, history of knee injury, and bony finger joint enlargements significantly described the race/sex changes in rates of KOA development and progression.

Methods

• This study enrolled Whites (WHs) (694 males, 929 females) and African–Americans (AAs) (92 males, 167 females) at risk for radiographic KOA.
• To estimate race and sex group differences in radiographic worsening, defined by Kellgren–Lawrence (K–L) and OARSI joint space narrowing (JSN), Cox shared frailty models were used.
•  Mixed effect models for repeated measures were used to estimate race– and sex–specific mean medial and lateral fixed joint space width (fJSW) over four years of follow–up, as well as annual loss of fJSW.

Results

• Risk of OARSI medial JSN grade worsening was higher among AA males than WH females (HR 2.28, [95%CI: 1.14–4.57]), though adjustment for KOA risk factors attenuated the association.
•  Compared to WH females, WH males had lower risk of K–L grade worsening (adjusted HR 0.75 [95%CI: 0.58–0.96]).
• Mean baseline medial fJSW (mm) was 6.49 in WH and AA males, 5.42 in WH females, and 5.41 in AA females. 
• Annual change in mean medial fJSW was greater in AA males (–0.19 mm/year) than in other subgroups (–0.09 WH males, –0.07 WH females, –0.10 AA females, p<0.0001).
•  AAs had less lateral fJSW at baseline and throughout follow–up, compared to WHs.