The associations of phase angle with the structural severity and quadriceps strength among patients with hip osteoarthritis: the SPSS-OK study

This study examined whether phase angle (PhA) is associated with hip osteoarthritis (HOA) severity and quadriceps strength in patients with HOA.

A series of 549 patients with HOA, obtained from the Screening for People Suffering Sarcopenia in the Orthopedic cohort of Kobe study, were analyzed. PhA and quadriceps strength were measured using bioelectrical impedance analysis and a handheld dynamometer, respectively. The HOA severity was graded using the Kellgren-Lawrence radiographic scale. We estimated (1) mean differences in PhA by differences in HOA severity and (2) mean differences in quadriceps strength by differences in PhA using general linear models.

The patients' mean age was 64.9 years, and 85% were women. A decreasing trend of PhA associated with increasing HOA severity was observed (P for trend < 0.001). PhA was statistically associated with a decrease in HOA grade 4 compared with that associated with HOA grade 1 (mean difference, - 0.40°; 95% confidence interval (CI), - 0.51° to - 0.30°). PhA per leg was associated with greater quadriceps strength per leg independent of age, sex, leg muscle mass, and HOA severity (mean difference per 1° increase, 3.80 Nm; 95% CI, 0.93 to 6.66). There was insufficient evidence of any difference in the association between PhA and quadriceps strength by HOA severity and sex (P for interaction = 0.07 and 0.06, respectively).

PhA gradually decreased with increasing HOA severity, especially in patients with end-stage HOA. Paying close attention to PhA might provide a key to increasing quadriceps strength, regardless of HOA severity. Key Points • PhA gradually decreased with progression of HOA, particularly in patients with end-stage HOA. • PhA was positively associated with quadriceps strength, regardless of HOA severity. • PhA could be one of the indicators of quadriceps strength in patients with HOA.