Anterolateral knee pain related to thrombosed lateral patellar retinaculum veins: Unusual anterolateral pain of the knee.

We describe the ultrasound (US) features of venous thrombosis involving the lateral patellar retinaculum (LPR) veins presenting as anterolateral knee pain. Four male patients, aged 16 to 35 years, were referred for lateropatellar pain with focal tenderness. In two cases, physical examination also demonstrated soft tissue swelling at the anterolateral aspect of the knee. In all four cases, US showed subcutaneous fat edema surrounding a thrombosis involving the LPR veins. Magnetic resonance imaging performed before US in one patient revealed only nonspecific subcutaneous fat edema and was therefore unable to make the correct diagnosis of LPR venous thrombosis.