Ultrasound appearance of knuckle pads

We describe the ultrasound appearance of knuckle pads.

Retrospective analysis of imaging in a series of five patients initially referred for evaluation of periarticular soft-tissue swelling of the hands involving the dorsum of the PIP and MP joints. Two patients had associated Dupuytren's contractures. Ultrasound and radiographs of the hands in all patients were reviewed and correlated with clinical history and physical exams.

Radiographs in four patients demonstrated dorsal soft-tissue thickening. Ultrasound exams showed increased dorsal subcutaneous thickening, with either diffuse or focal hypoechoic areas corresponding to the areas of soft-tissue fullness identified on physical exam. No erosions or synovial proliferation were identified either by radiographs or ultrasound of the underlying joints.

Knuckle pads can sometimes be difficult to distinguish from synovitis on physical examination. Musculoskeletal ultrasound can quickly identify these superficial lesions and exclude underlying synovial proliferation.