Clinical Factors for Predicting Synovial Hypertrophy in Early Haemophilic Arthropathy on Prophylaxis: A Cross‐Sectional Study of Patient‐ and Joint‐Level Analyses Using Musculoskeletal Ultrasound

ABSTRACT Introduction Early identification of synovial hypertrophy is critical for preventing irreversible changes in haemophilic arthropathy (HA). Although prophylaxis has improved joint outcomes, it remains unclear which patients and joints in early HA should be prioritised for musculoskeletal ultrasound (MSKUS) screening. Aim To identify the predictors of synovial hypertrophy at the patient and joint levels in early HA. Methods We enrolled patients with haemophilia aged 6–49 years with mild joint damage (Arnold–Hilgartner grades I–III). Elbows, knees and ankles were examined using MSKUS. Patient‐level factors included age, body mass index, haemophilia characteristics, adherence and activity. Joint‐level factors included symptoms, recent bleeding, physical findings and radiographic scores. Logistic regression was applied to patient‐level predictors and mixed‐effects models to joint‐level predictors. Results In total, 203 joints from 40 patients were evaluated; synovial hypertrophy was identified in 82 joints (34 patients), most frequently in the knees (54.5%), followed by the elbows (38.9%) and ankles (22.2%). Adult age was the only significant patient‐level predictor of synovial hypertrophy (odds ratio, 5.2; p = 0.001). At the joint level, no examined factors were significantly associated with synovial hypertrophy. Among asymptomatic joints, 37.9% demonstrated synovial hypertrophy (23.7% in paediatric patients vs. 56.9% in adults), with elbow involvement showing no significant age‐related differences (34.4% vs. 40.7%, p = 0.79). Conclusions Patient‐ and joint‐specific findings alone are insufficient to predict synovial hypertrophy. MSKUS may be used routinely to enhance early detection in patients with HA on prophylaxis. Elbow synovial hypertrophy warrants attention from paediatric patients as one of the earliest stages of the disease.