抄録
A 12-year-old boy fell while playing football, injuring his left knee joint. About 4 months later, he visited our hospital because the knee joint had suddenly “locked”, making extension impossible.
On examination, the range of motion was -60 degrees of extension, and 145 degrees of flexion without any sign of inflammation or fluid retention.
CT and MRI views of the knee joint revealed a bone tumor (exostosis) at the medio-proximal site of the tibia.
Suspecting this tumor to be the cause of the locked knee, we immediately performed surgical exploration of the knee joint, and noted a bone tumor with a hook-shaped cartilaginous cap on the top, arising from the attachment of the pes anserinus, and also noted that the tendons in the pes anserinus had been partially injured.
These findings revealed that the mechanism responsible for knee locking had been trapping of the tendons in the pes anserinus by the bone tumor. We therefore excised and removed the bone tumor.
After surgery, the patient recovered well, regaining the full range of knee joint motion.
We are confident that surgical excision of this type of bone exostosis may be the first choice of treatment for some cases of locked knee.
