Do Weight-Bearing Knee Digital Radiographs Help to Track the Severity of OA?

Weight-bearing radiographs are preferred for joint space width (JSW) assessment in OA, sometimes non-weight-bearing radiographs are also done. This study aims to evaluate (1) The knee JSW in weight-bearing (WB) and non-weight-bearing (NWB) X-ray images. (2) Quadriceps angle (Q angle) at weight-bearing and non-weight-bearing positions.

Patients above 50 years old with symptoms (knee pain, functional limitations, and crepitus) from April 2019 to November 2019 were included in the study. Expert exclude patients with post-surgical evaluation, trauma, and infection. JSW and Q angle measurements with respect to weight-bearing and non-weight-bearing positions were made by the same medical expert to avoid inter-observer variation.

Medial knee JSW varies from 0.49 to 5.75 mm in weight-bearing radiograph and 0.53 mm to 6.16 mm in non-weight-bearing radiograph. Q angle varies from 8.72° to 14.58° in weight-bearing position and 10.13° to 14.92° in non-weight-bearing position. Q angle (< 11.72°) and medial JSW (< 3.725 mm) were found to be significantly associated with the rapid progression of knee varus OA (p < 0.001).

NWB digital X-ray images overestimate early and underestimate severe OA. There is a possibility of increasing tibia internal rotation and reduction of joint space width in a standing position (WB) as the phase of knee OA diagnosis. These findings show that weight-bearing knee joint radiographs are helpful to track the progression of knee varus OA and have strong clinical usage than non-weight-bearing radiographs. Patients whose Q angle and knee JSW measures are below the limitations need more attention.