Tibial nerve entrapment by a Baker cyst: case report.

We report a rare case of degenerative joint disease of both knees, complicated by a Baker cyst. Our emphasis is on the role of electromyography and electrodiagnosis in the localization of this nerve entrapment syndrome. The patient presented with pain and swelling; venography revealed deep venous thrombosis of the right calf, including the popliteal and proximal superficial femoral vessels. The patient responded well to bed rest, analgesics, intravenous heparin and subsequent Coumadin anticoagulation, and was discharged two weeks later. Five weeks after onset of these acute problems, nerve conduction studies were done, leading to a diagnosis of Baker cyst with nerve entrapment. He responded well to knee joint aspiration and intraarticular prednisolone injection. Some evidence of improvement in the flexor hallicus longus muscle was detected at three-month follow-up.