Abstract
This case concerned a female patient with a complaint of pain in the anterior region of her left knee during and after sports activities, followed by joint blockage three months ago. From imaging examinations, simple radiography of the knee was normal and magnetic resonance showed a solid expansive mass, possibly corresponding to soft-tissue chondroma or focal nodular synovitis. Arthroscopic resection of the lesion was performed, and the diagnosis of diffuse giant cell tumor resembling localized pigmented villonodular synovitis (PVNS) was made from the result of the anatomopathological examination. The patient presented good clinical evolution, with disappearance of symptoms and return to physical activities.