The radiographic predictors of symptom severity in advanced knee osteoarthritis with varus deformity

Information concerning the abilities of radiographic parameters to predict the symptoms of advanced osteoarthritis (OA) of the knee would be valuable, because plain knee radiographs are used as one of the primary tools for the selection of treatment modalities. We aimed to identify the radiographic predictors of symptom severity in patients with varus knee OA advanced enough to warrant total knee arthroplasty (TKA). In 341 knees with primary varus OA warranting TKA, pertinent radiographic features of the medial and lateral tibiofemoral joint (TFJ), and the patellofemoral joint (PFJ) were assessed separately and scored. In addition, TF alignment was assessed on standing full-limb radiographs. Symptoms and functions were evaluated using WOMAC pain and function scores. In the univariate analyses with generalized estimating equations (GEE), multiple radiographic features (subluxation of the TFJ, overall severity of the medial TFJ, and degree of TF varus alignment) were associated with poorer WOMAC function scores, whereas only the degree of TF varus alignment was associated with poorer WOMAC pain scores. None of radiographic parameters in the PFJ or lateral TFJ (except TFJ subluxation) was associated with WOMAC scores. Multivariate analyses revealed that the degree of TF varus alignment was the strongest predictor of poorer WOMAC pain and function scores. We propose that extent of TF varus malalignment should be considered as the primary indicator of objective disease severity when selecting treatment options for patients with advanced knee OA.