Tophaceous gout presented as a posterior cruciate ligament mass and addressed by posterior knee arthroscopy: A case report and literature review

Abstract

Background: Tophaceous gout, when manifested as a posterior cruciate ligament (PCL) mass within a joint, is uncommon. Differentiating it from other intraarticular pathologies, notably tenosynovial giant cell tumors (TGCT), previously known as pigmented villonodular synovitis (PVNS), proves challenging. This difficulty arises primarily from the resemblances in their presentation on standard radiological tools such as MRI. Notably, the lesion appearance in tophaceous gout closely aligns with that of TGCT. Case report: We present a case of intraarticular tophaceous gout in a 35-year-old male localized in the posterior chamber of the left knee, particularly around the PCL, leading to posterior knee pain and locking. MRI depicted a diffuse lobulated mass encircling the PCL. During arthroscopic debridement, chalky urate crystals were observed on the articular surfaces during the procedure. Biopsies confirmed the diagnosis of intraarticular tophaceous gout, and the patient showcased significant postoperative improvement. Conclusion: While the diagnosis of soft tissue masses in the knee, notably TGCT and tophaceous gout, poses challenges using conventional radiological tools, our literature review indicates that tophaceous gout in the PCL is seldom suspected in the initial diagnosis of intraarticular tumors due to its resemblance to TGCT on MRI. We emphasize the need for a diagnostic protocol to effectively discern intraarticular tumors of the knee.

Keywords

• Gout
• Tophaceous
• Knee joint
• Posterior cruciate ligament
• PCL
• TGCT