An unusual case of foreign body knee that spontaneously migrated inside and out of the joint: arthroscopic removal.

Cause of acute knee pain and locking episodes in a young sports person can be due to foreign bodies which penetrated unnoticed into the joint cavity. Here we report an unusual injury of this kind where a glass foreign body remained in the subcutaneous tissue for many years and then migrated late into the knee joint cavity. Complaints occurred for the first time in adult age. Arthroscopy revealed a circular defect in the posterior capsule beyond which a 1.6 cm glass foreign body was lying in an extra capsular location. The late and episodic migration of the glass piece into the joint from its extracapsular location produced symptoms of acute pain and locking. There is no reported case of such spontaneous and episodic migration of a glass foreign body inside and out of the knee joint resulting in acute episodes of pain and locking during sporting activity mimicking a torn meniscus or a chondral lesion. This report highlights the importance of accurate history taking, thorough physical examination, besides describing this unusual extra capsular location of the glass foreign body during arthroscopic surgery.