Introduction: Diabetes mellitus has a broad range of complications, including diabetic Charcot neuroarthropathy of the knee. This complication is a destructive joint disorder by way of nerve damage and subsequent unfelt microtrauma. Another condition that can cause severe, but painless osteoarthropathy of the knee is synovial sarcoma. This type of tumour is a soft tissue neoplasm that predominantly presents within, or near large joints of the lower extremities. Synovial sarcoma can cause bone invasion, bone erosion, or both. These bone changes can then contribute to joint destruction. The overlap between the clinical features of Charcot knee and synovial sarcoma can be significant. Therefore, differentiating the two can be complicated. There have been reported cases of incidental findings of synovial sarcoma during treatment of knee arthropathy. Both synovial sarcoma and Charcot arthropathy require time-sensitive management, and a timely diagnosis may help reduce the risk of a poor prognosis.
Case presentation: We present a case of diabetic Charcot neuroarthropathy of the knee. This case was complicated by CT findings that were suspicious for synovial sarcoma. Furthermore, we reviewed current literature for Charcot knee and synovial sarcoma. This literature review included additional evaluations that should be considered when differentiating between these conditions and other joint destructive disorders. This case was handled by the Department of Orthopedics, Milton Cato Memorial Hospital, Kingstown, Saint Vincent and the Grenadines.
A 52-year-old black woman with an eighteen-year history of uncontrolled type II diabetes mellitus presented with nine months of chronic and progressive right knee swelling. On primary survey, the knee was moderately swollen with crepitus. Fluid from the knee joint was aspirated with no signs of pathology. Osteoarthritis remained the working diagnosis. A corticosteroid injection was administered, and the patient was given a knee brace and crutches with non-weight bearing instructions. Furthermore, plain film X-ray imaging was performed which revealed degenerative joint changes to the knee. On secondary survey, the knee became severely swollen. On physical examination, the right knee joint presented with significant effusion, increased warmth, and crepitus. There was mild tenderness only with full knee flexion. Both anterior and posterior draw tests were positive. In addition, the knee joint was capable of hyperabduction and hyperadduction of the lower leg, opening the joint medially and laterally respectively. Plain film X-ray imaging revealed a markedly edematous knee joint with extensive erosion to the femur and tibia. Periarticular debris and fragmentation were also noted. Given the patient’s history of diabetes mellitus, diabetic Charcot neuroarthropathy was included in the differential diagnosis. A CT scan was ordered, and the impression indicated suspicion for synovial sarcoma. As a result of the CT findings, synovial sarcoma was added to the differential diagnosis. Due to the extensive destruction of the knee joint surgical intervention was indicated. The patient was scheduled for an arthrodesis with the intention of mass biopsy. During surgery, the knee joint was opened with direct visualization of the synovium. There was no mass or features of malignancy to warrant biopsy. Post-surgery, the patient was placed in a cast for ten weeks. The patient was diagnosed with diabetic Charcot neuroarthropathy of the knee, and the symptoms markedly resolved four months post operation.
Discussion: This literature illustrates prompt assessments to consider when diagnosing diabetic Charcot neuroarthropathy and synovial sarcoma of the knee. These assessments lead to quicker diagnosis, ideal treatment, and optimal patient outcomes.PDF
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