Tarsal tunnel syndrome is defined as an extrinsic and/or intrinsic compressive neuropathy of the posterior tibial nerve or one of its branches. Its causes include venous insufficiency. Clinical case: 51 year-old female patient from León, Guanajuato. Hypertensive, with Guillain-Barré syndrome for eight years, vascular insufficiency and obesity. Her condition started with left ankle and heel pain; she was treated with NSAIDs and rehabilitation and achieved partial improvement. X-rays and MRI of the left ankle showed posterior impingement. She underwent arthroscopy and improved but one month later she presented with severe pain in the left ankle and sole and dysesthesias. Electromyography showed a lesion of the posterior tibial nerve. We had the patient's case history, preoperative tests, and dorsoplantar and lateral X-ray views. The arthroscopic diagnosis was Flexor Hallucis Longus (FHL) tendinitis, synovitis and posterior ankle impingement. Synovectomy, decompression and smoothening of the FHL tendon were performed. The patient did poorly and underwent electromyography with axonotmesis of the medial plantar branch. After the nerve was released, Lazorthes venous plexus was found to be tortuous and compressing the entire nerve tract. The possible causes for this include intrinsic compression secondary to tumors, and anatomical changes of the tarsal tunnel. However, less often varices may confound the diagnosis and cause irreversible damage if not treated timely. The patient is currently pain free and can walk, has mild dysesthesias of the first toe and limited flexion.