• Case report
• Extra-articular knee locking
• Impingement
• Osteochondroma
• Pes anserinus
• Surgery
• Tibia

• Medullary involvement
• Pes anserine bursitis
• Tibial cortical scalloping

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.

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.

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.

• Children
• Hereditary multiple exostoses
• Osteochondromas
• Paediatrics
• Pes anserinus syndrome
• Tibia

This study investigated the boundary of anserine bursa with the recommended injection site and shape on the insertion area of pes anserinus (PA), with the aim of improving clinical practice. Eighty six legs from 45 Korean cadavers were investigated. The mixed gelatin solution was injected to identify the shape of anserine bursa, and then the insertion site of the PA tendons was exposed completely and carefully dissected to identify the shape of the PA. The sartorius was inserted into the superficial layer and gracilis, and the semitendinosus was inserted into the deep layer on the medial surface of the tibia. The number of the semitendinosus tendons at the insertion site varied: 1 in 66% of specimens, 2 in 31%, and 3 in 3%. The gracilis and semitendinosus tendons were connected to the deep fascia of leg. Overall, the shape of the anserine bursa was irregularly circular. Most of the anserine bursa specimens reached the proximal line of the tibia, and some of the specimens reached above the proximal line of the tibia. In the medial view of the tibia, the anserine bursa was located posteriorly and superiorly from the tibia's midline, and it followed the lines of the sartorius muscle. The injection site for anserine bursa should be carried out at 20° from the vertical line medially and inferiorly, 15 or 20 mm deeply, and at the point of about 20 mm medial and 12 mm superior from inferomedial point of tibial tuberosity.

• Anserine bursa
• Bursa injection
• Cadaver
• Pes anserinus