Knee locking and pain mimicking lateral meniscal tear due to unusual location of localized pigmented villonodular synovitis: a diagnostic surprise

Giant Cell Tumor of the Patella Tendon Sheath Presenting as a Painful Locked Knee

Patient: Male, 26

Final Diagnosis: Giant cell tumor of the patella tendon seath

Symptoms: Efusion • locking knee • pain

Medication: None

Clinical Procedure: Arthroscopy and open resection of the tumor

Specialty: Orthopedics and Traumatology

Localized form of pigmented villonodular synovitis of the knee: the meniscal mime

The localized form of pigmented villonodular synovitis of the knee is a rare condition with non-specific symptoms. This makes diagnosis especially difficult when the meniscus is affected. A full assessment with several imaging modalities can help support the preoperative diagnosis. But in the case reported here, the full clinical and paraclinical assessment (X-rays, CT arthrography and MRI) was wrong--the localized form of pigmented villonodular synovitis had mimicked a lateral meniscus injury and was only detected during arthroscopy. The lesion was excised surgically and the diagnosis was confirmed through postoperative histopathology.