Clinico-radiological diagnosis and grading of rapidly progressive osteoarthritis of the hip.

Due to the current lack of standard definitions for rapidly progressive osteoarthritis of the hip (RPOH) in the literature, this observational study aimed to describe new diagnostic criteria and a grading system for the disease.From a consecutive series of patients undergoing total hip replacement, 2 groups were selected: 1 with RPOH and 1 with primary hip osteoarthritis (POH), and their clinical, paraclinical, and demographic data were compared. The newly proposed clinico-radiological diagnostic criteria are based on characteristics of pain, joint mobility, and radiological assessment. The radiological grading system's inter- and intraobserver reliability was assessed through serial evaluations by 2 blinded reviewers.From the total 863 cases, 82 cases (9.5%) of RPOH were identified and compared with 107 cases of POH. Mean age and disease bilaterality were similar, with a predominance of female patients in the RPOH group (P = 0.03). There were significant differences between the 2 groups in disease onset and aggravation, and intraoperative blood loss. The grading system showed significant inter- and intraobserver agreement (weighted kappa 0.93, and 0.89).Our study presents distinctive, easily recognizable clinico-radiological characteristics of RPOH and confirmed the inter- and intraobserver reliability of the newly proposed grading system.