Hoffa’s fat pad tumours: What do we know about them?

We report on a group of patients with tumours in the Hoffa’s fat pad (HFP), their clinical presentation, histological type and treatment, including two synovial sarcomas with their clinical follow-up, which have not been described previously in the literature. We performed a retrospective review of our prospectively collected database of 25 cases of HFP tumours with at least six months follow-up. The gender, age at presentation (over and under 16 years of age), clinical features, history of trauma, treatment chosen, and complications were recorded. The mean age of the patients was 32 years (three to 47). Six patients were under 16 years old. Pain was the most common symptom, present in 92 % (n = 23/25). The final diagnoses included 23 (92 %) benign tumours and two (8 %) malignant tumours. The most common benign tumour was pigmented villonodular synovitis (PVNS) (48 % n = 12). The two malignant tumours were synovial sarcomas and both presented in patients under 16 years old. Hoffa’s fat pad tumours are an uncommon and rarely diagnosed group of lesions that can be misinterpreted as any knee pathology. Although the majority of HFP tumours are benign, malignant tumours should be considered in the differential diagnosis for the paediatric population.