The radiographic joint space width in clinically normal hips: effects of age, gender and physical parameters

The aim of the study was to assess the relationship of the radiographic joint space width (JSW) in the hip with age and a variety of physical parameters in a clinically non-arthritic population in order to identify potential age-related changes.

One hundred and eighteen patients (58F/60M, age range 20-79 years) who underwent supine abdominal radiography for non-rheumatological indications and had no hip pain were evaluated. Height, weight and leg lengths were measured. JSW was quantified manually by a dial caliper, and femoral head diameters were determined for each hip.

Overall, JSW was 3.61mm+/-0.58 (mean+/-SD) in the right (R) and 3.63mm+/-0.59 in the left (L) hip (range 2.34-6.1mm). There was no age-related decline in the JSW, either by decade (P=0.5 and 0.6, for R and L hips, respectively), or by individual age (Spearman's rho=-0.108 and 0.057, P=0.3 and 0.5 for R and L hips, respectively); similarly, no age-related changes were observed when each gender was analyzed separately. Women had significantly narrower hip JSW than men (P=0.001 and 0.01, R and L hips, respectively). However, gender was no longer significant after height was taken into account (P=0.26 and 0.45, for R and L hips, respectively). JSW correlated significantly with height, weight (which also correlated with height) (r=0.31/0.27 and 0.29/0.28 for height and weight R/L, respectively, P<0.004 for each), but not with body mass index (P=0.62 and 0.57, R and L, respectively). Hip JSW significantly correlated also with femoral head diameter and leg length (r=0.38/0.29 and 0.25/0.19 for femoral head and leg length, R/L, respectively).

No effect of aging was detected on the radiographic JSW of the hip among normal individuals even at advanced ages. In contrast, height, femoral head diameter and leg length were directly related to JSW.