Are Weight-Bearing Knee Digital Radiographs better for assessment of Severity of OA?

Tamilnadu, India: Weight-bearing radiographs are preferred for joint space width (JSW) assessment in OA , sometimes non-weightbearing (NWB) radiographs are also done.

Patients above 50 years old with symptoms (knee pain, functional limitations, and crepitus) were included in the study. Expert excluded 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.

The observations of the study were:

• Medial knee JSW varies from 0.49 to 5.75 mm in weight-bearing radiograph and 0.53 mm to 6.16 mm in nonweight-bearing radiograph.

• Q angle varies from 8.72° to 14.58° in weight-bearing position and 10.13° to 14.92° in nonweight-bearing position.

• Q angle (<11.72°) and medial JSW (<3.275) were found to be significantly associated with the rapid progression of knee varus OA (p<0.001).

The authors concluded that - Outcomes with respect to weight-bearing and non-weight bearing radiographs/positions vary significantly. For evaluating varus deformity, weight-bearing radiographs are necessary. Non-weight-bearing radiographs appear to exaggerate the deformation in early varus deformity, although they appear to underestimate it in advanced deformation. The result of the study shows that knee mJSW measurements from digital radiographs are relatively the same for mild and severe cases than moderate to severe cases in both WB and NWB positions. From the study, we found that there is no significant JSW difference between non-weight-bearing and weight-bearing radiographs in the initial stages of OA but patients are unable to put load due to pain. Therefore, using non-weight-bearing radiographs rather than weight bearing radiographs to analyze knee joint space width is very helpful in the initial stages of OA. We noticed a tendency to increase joint space width and external rotation of the tibia during weight-bearing position. This result is particularly significant considering that the radiographic positions are the important factors for the diagnosis of OA. These findings show that weight-bearing knee radiographs are useful to track the progression (severity) of knee varus OA than non-weight-bearing radiographs. Patients whose Q angle and knee JSW measures are below the limitations need more attention.

Further reading:

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

S. Sheik Abdullah, M. Pallikonda Rajasekaran.

Indian Journal of Orthopaedics (2022) 56:664–671

https://doi.org/10.1007/s43465-021-00560-w