Ankle canal syndrome is a syndrome caused by pressure on the posterior tibial nerve or its branches as they pass through the bony fiber canal below the flexor support zone behind the inner ankle, mostly due to excessive pressure or tissue in the canal, resulting in pressure on the posterior tibial nerve and its branches during dorsiflexion or plantarflexion of the ankle. The disease is not easily noticed clinically, so it is often misdiagnosed. It is most often seen in young adults who exercise frequently. 1. Narrowing of the lumen of the ankle canal 1. Trauma: distal tibial fracture, post-articular fixation of ankle sprain or crush injury, heel fracture, post-traumatic edema and late fibrosis causing adhesion of the posterior cavernous nerve in the ankle canal. 2.Posterior cavernous vein stasis, embolic phlebitis. 3, foot valgus deformity, producing increased tension in the flexor support band and the fiber starting point of the abductor digitorum brevis. 2. Excessive tissue in the ankle canal 1. tenosynovitis, synovial hyperplasia or tenosynovial cyst of the posterior tibial muscle, flexor digitorum brevis or flexor digitorum brevis tendon. 2.Rheumatoid arthritis, synovial tissue edema and inflammation. 3.Congenital anatomical abnormalities, such as hyperplastic or hypertrophied paraspinatus bunion muscle. 4, Weight gain (excessive fat accumulation). 5, Posterior cavernous vein aneurysm. 6, Nerve sheath tumor of the posterior cavernous nerve and its branches. 7, Tissue hyperplasia in the ankle canal caused by certain drugs. 3, The fascial fiber arch of the abductor bunions produces compression at the entry of the medial plantar nerve or lateral plantar nerve, especially in foot valgus. Because the posterior tibial nerve vascular bundle is surrounded by longitudinal fiber interval and separated from the tendon interval in the ankle canal, it is relatively little pulled by the ankle joint activity, but the ankle canal is an inelastic bone fiber canal, so the posterior cavernous nerve and its branches can be compressed in the ankle canal for various reasons: firstly, it causes local ischemia, the posterior tibial nerve has rich blood supply and its nerve fibers are very sensitive to ischemia; secondly, the posterior tibial nerve is sensitive to ischemia due to various reasons inside and outside the ankle canal, The pressure in the ankle canal rises sharply after the compression of the posterior tibial nerve, resulting in a decrease in blood flow to the small arteries or veins in the epicardium of the posterior cavernous nerve, which leads to hypoxia of the nerve, and then capillary endothelial cell damage, protein leakage, and edema, which in turn increases the pressure in the ankle canal and further compresses the vessels in the epicardium of the nerve. As a result, early in the lesion, the proximal end of the compressed nerve is swollen, while the distal end is pale and stiffer to the touch. As the continuity of the nerve remains intact, the nerve segment appears microscopically edematous, with cell proliferation and fibrosis and altered axial bundle elements, and the nerve damage can be cured if decompression is given promptly.