Diaphyseal Aclasis With Pes Anserinus Syndrome

We describe the case of a 20-year-old man who presented with a bony swelling over the medial proximal tibia that caused pain along the pes anserinus tendons, and a history of multiple asymptomatic bony swellings. Wide extraperiosteal resection of the swelling relieved the symptoms with a good outcome within a year. This report describes the pictorial pathoanatomy of a relatively rare association of pes anserinus syndrome caused by osteochondroma in an adult patient. Proximal tibial osteochondromas can also present as pes anserinus syndrome in adult patients with diaphyseal aclasis. Large swellings require wide excision to relieve the stretching pain of pes tendons.