Liposynovitis prepatellaris in athletic runner (Hoffa's syndrome): case report and review of the literature.

A 37-year-old male patient, who is an athletic runner, developed anterior knee pain of acute onset after prolonged running and swelling of his right knee. The patient experiences more pain when he flexes the knee and a sense of catching together with grade 1 effusion. The patient was clinically suspected to have internal derangement and MRI study of his right knee was ordered to exclude such possible diagnosis. The MRI study revealed the following: a hypointense lesion in the infrapatellar pad of fat in T2-weighted images (WI), postcontrast T1 WI with fat saturation demonstrated no enhancement, and STIR sequence showed slightly hyperintense lesion with minimal knee effusion. The MRI findings supported the diagnosis of Hoffa's syndrome, and arthroscopic resection of the fat pad was performed. There was a significant improvement in the symptoms and function after the surgery.