Pes Anserinus Syndrome Caused by Osteochondroma in Paediatrics: A Case Series Study.

Introduction: Osteochondroma is a common benign bone tumor, protruding from the underlying normal bone. Osteochondromas can cause pain depending on their location and size. The pes anserinus is located at the proximal medial side of the tibia, where the tendinous insertions of the sartorius, gracilis and semitendinosus muscles collectively attach. Pes anserinus syndrome, or anserine bursitis, is a painful condition of the pes anserinus, and is more common in adults typically with overweight females. The occurrence of pes anserinus syndrome is rare in the paediatric population.

Results: In the current case series, five patients with pes anserinus syndrome due to proximal tibial osteochondroma are reported. Pain was present in all cases, with snapping in one case. The average age of the patients was 13 ± 1.2 years, ranging from 12 to 15 years. Three patients had a single osteochondroma, and two patients had hereditary multiple exostoses. The sizes of the osteochondromas on plain radiographs varied from 0.5 to 2.5 cm, with an average of 1.46 ± 0.83 cm. All lesions characteristically were located at the medial-posterior edge of the proximal tibia. The symptoms resolved in four cases with surgical resection, and persisted in one non-resected patient.

Conclusion: The characteristic location of the osteochondroma causes pes anserinus syndrome, even though the lesion is small. The diagnosis of osteochondroma or pes anserinus syndrome may be overlooked when it occurs in a paediatric population. The symptoms seem to be consistent, and resection of the osteochondroma is necessary for treatment.