Divergent Sign: a Case Series Describing a Novel Radiographic Finding of Posteromedial Hip Osteoarthritis

While hip osteoarthritis (OA) is often diagnosed by plain films, posteromedial hip OA is harder to visualize, thus risking underdiagnosis among patients with symptomatic posteromedial hip OA but unremarkable plain hip and pelvis radiographs. The divergent sign, or apparent asymmetric widening of the superolateral joint space on anteroposterior view, may be a useful indicator of posteromedial OA. We present a case series of 19 patients with posteromedial hip OA diagnosable via the divergent sign and confirmed with magnetic resonance imaging and intraoperative findings. Seventeen of these patients underwent total hip arthroplasty with successful outcomes and minimal postoperative complications, while the other 2 elected conservative management. We propose this radiographic sign should prompt clinicians to better evaluate for posteromedial hip OA with advanced imaging to sooner diagnose this condition.