Temporal trajectory and predictors of hemiplegic shoulder pain after stroke: a 12-month longitudinal clinical-ultrasound study

BACKGROUND: Hemiplegic shoulder pain (HSP) is a frequent complication after stroke. Although HSP is considered a multifactorial condition, the temporal sequence through which different mechanisms contribute to pain remains poorly understood, mainly due to the lack of longitudinal studies starting from the acute phase and integrating imaging data. AIM: To describe the 12-month temporal trajectory of hemiplegic shoulder pain after stroke and to identify time-specific clinical and ultrasonographic predictors of pain intensity. DESIGN: Prospective Longitudinal Observational Study. SETTING: Inpatient stroke unit and neurorehabilitation facilities. POPULATION: Patients with first-ever ischemic or hemorrhagic stroke and contralateral hemiparesis. METHODS: Patients were evaluated within 72 hours after stroke onset and at 1, 3, 6, and 12 months. Shoulder pain during passive mobilization was assessed using the Numerical Rating Scale. Clinical evaluation and standardized shoulder ultrasonography were performed at each time point. Univariable and multivariable linear regression analyses identified independent predictors of pain. RESULTS: Seventy-seven patients were enrolled. Pain increased from the acute phase to a peak at 3 months and progressively decreased thereafter. Reduced passive range of motion was consistently associated with pain. In the acute phase, pain was associated with glenohumeral subluxation. Adhesive capsulitis emerged at 1 month, while at 3 months pain was associated with subluxation, capsulitis, and tendon tears. In the chronic phase, tendon tears became the main determinant of residual pain. CONCLUSIONS: Hemiplegic shoulder pain follows a temporally differentiated multifactorial pattern, with distinct mechanisms prevailing at different stages after stroke. CLINICAL REHABILITATION IMPACT: Identifying phase-specific mechanisms of hemiplegic shoulder pain supports targeted, time-specific preventive and therapeutic strategies in neurorehabilitation.