Enthesopathic erosive lesions of patella and tibial tuberosity in juvenile ankylosing spondylitis. Anatomico-radiological study of a case with tibial bursitis.

The authors report the case of a 20-year-old joiner suffering from ankylosing spondylitis, with recurrent knee effusions from the age of 11 and radiological evidence of sacro-iliac involvement. The patient presented with pain and bone erosions localized to the sites of tendinous attachments in the upper pole of the left patella and in tibial tuberosities. On both sides an inflammation of deep infrapatellar bursa was observed on anatomical examination. These destructive lesions are considered as rare forms of the erosive enthesopathy which has been described in ankylosing spondylitis, particularly on spine and calcaneum. They could be considered as highly localized forms of algodystrophy.