Intra-articular venous malformations of the knee

Intra-articular venous malformations (IAVM) of the knee represent a rare group of low-flow vascular malformations, mainly reported in the literature as synovial hemangiomas, usually with an onset in early childhood. The main symptoms and signs are knee pain, swelling, and hemarthrosis. These lesions are slowly progressive and can lead to chronic synovitis and joint damage. Confusing nomenclature and classification of these lesions have often led to misdiagnosis and inappropriate treatment. We report our experience in the treatment of 14 consecutive patients affected by knee IAVM.

We carried out a retrospective study based on the review of the medical records and diagnostic imaging of the patients admitted to our department from October 1999 to June 2009, and discharged with the final diagnosis of IAVM of the knee.

We observed 14 consecutive patients (8 boys, 6 girls); the median age at symptom onset was 5 years (range, 2.5 to 13 y). Magnetic resonance imaging was diagnostic in all cases. Surgical resection associated with a wide synoviectomy was the therapeutic procedure of choice in all cases. Within 6 months after surgery and physiotherapy, all the patients were symptom free with a full or at least acceptable knee range of motion. CD34 staining carried out in the last 7 cases of our series showed labeling of the endothelium of the thick-walled vessels, whereas the endothelium of the thin-walled vascular spaces was not stained. This finding of unstained vascular spaces suggests that a component of lymphatic vessels mixed with dysplastic blood vessels may be frequently present in these abnormalities.

Magnetic resonance imaging plays a pivotal role in identifying the lesion. Surgical excision is always indicated and should be performed as early as possible to avoid lesion progression and to reduce the risk of chondral degeneration. According to the microscopic features of our resected specimens, we suggest that these lesions of the knee should be more properly named as IAVM instead of hemangiomas.

Level IV.