Normal ankle mobility averages 48° of plantarflexion and 18° of dorsiflexion. When the knee joint is straight, the dorsiflexion of the ankle joint is ≤10°, which is called horseshoe foot deformity (equinus). Causes of horseshoe foot include: ① soft tissue contracture (gastrocnemius and/or Achilles tendon, joint capsule); ② bony obstruction (bony bulge in front of the ankle joint); ③ neuromuscular dysfunction (spastic horseshoe foot, such as cerebral palsy, stroke, traumatic brain injury, diabetes mellitus, etc.). Functional gastrocnemius contracture refers to the shortening of the gastrocnemius muscle without the abnormality of the innervation and the lesion of the muscle itself. The consequences of this shortening may cause imbalance of the muscle strength of the foot, abnormal gait and the destruction of part of the foot and ankle structure. 1. Anatomy 1. The gastrocnemius muscle starts from the medial and lateral femoral ankle with two heads, the medial head is thicker than the lateral head, and the two heads also send out branches to attach to the posterior knee capsule and the N oblique ligament. The two heads merge to form a muscle belly, and the uncuspid end fuses with the flounder tendon to form a strong Achilles tendon that ends at the heel node. The gastrocnemius muscle passes through three joints: the knee, the ankle and the subtalar joint. The muscle contraction makes the foot plantarflexion and flexion of the lower leg; in standing, fixes the ankle joint and prevents the body from leaning forward. 2, the flounder muscle is a wide flat muscle, located in the deep surface of the gastrocnemius muscle, from the head of the fibula and the upper fibula, the medial edge of the tibia and the flounder muscle line. The muscle is a two-joint muscle, passing through the ankle joint and the subtalar joint. This muscle is the same as the gastrocnemius, except that it does not participate in the flexion of the calf. The gastrocnemius and the flounder muscle have a total of three heads at the beginning, so the two are also known as the calf triceps. 3, the Achilles tendon is about 15cm long, is the thickest tendon in the human body, by the calf triceps (flounder, gastrocnemius, internal and external head) tendon in the heel above about 15cm fusion formation. The fibers of the gastrocnemius and hallux valgus muscles rotate counterclockwise after forming the Achilles tendon, and the angle of rotation varies from 30°-150° depending on the individual. II. Pathology The cause of functional gastrocnemius contracture is not clear. It may be related to its crossing of the knee and ankle joints. Sitting and lying positions reduce the tension of the gastrocnemius muscle, whether it makes it easy to become shorter. Once contracture of the gastrocnemius occurs, the following lesions may be triggered or associated: 1. Anterior ankle impingement sign When the posterior structures of the ankle limit the dorsiflexion of the ankle joint, the anterior pressure on the ankle joint increases. This subsequently causes inflammation or cartilage damage in the anterior aspect of the ankle. Bony redundancy forms in the anterior ankle to reduce the pressure per unit area. 2. Metatarsal tendonitis Because heel lift occurs earlier in gait in patients with gastrocnemius contracture, dorsiflexion of the metatarsophalangeal joint strains the metatarsal tendon membrane (winch mechanism), and the metatarsal tendon membrane is subjected to greater stress and is prone to tears at the starting point. Among 310 patients investigated in our outpatient clinic, 19 cases suffered from metatarsal tendinitis, of which 14 cases (73.7%) also had gastrocnemius contracture and 1 case (5.3%) had combined Achilles tendon contracture. 3, posterior tibial tendon insufficiency PTTD is often accompanied by gastrocnemius contracture, but it is unclear who is the cause and effect. The shortened gastrocnemius muscle aggravates the heel exostosis and puts the midfoot under greater stress. To compensate for the shortened gastrocnemius tendon, the hindfoot is turned out and the mid forefoot is rotated forward to achieve maximum ankle dorsiflexion. Our survey of 88 patients with flat feet found 53 cases (60.2%) combined with gastrocnemius contracture and 8 cases (9.1%) combined with Achilles tendon contracture. 5, bunions Excessive rotation of the midfoot forward produces excessive activity in the medial sequence of the foot. Rogers found that 58% of bunion patients had soft tissue clubfoot preoperatively. mann and Coughlin noted that clubfoot may affect the long-term outcome of bunion surgery. In a survey of 196 bunion patients at our institution, we found 115 cases (58.7%) with gastrocnemius contracture and 21 cases (10.7%) with combined Achilles tendon contracture. 6, metatarsalgia Gastrocnemius contracture increases the stress on the forefoot at the end of weight-bearing. It often manifests as a painful callus on the metatarsal side of the central metatarsal. In severe cases, it can cause metatarsal head cartilage damage and metatarsophalangeal joint osteoarthritis. 7, diabetic foot ulcers The increased stress on the forefoot and midfoot makes the diabetic foot more prone to ulcers and rocker bottom deformities. III. Clinical examination In the state of knee extension and knee flexion, respectively, the ankle joint is passively dorsally extended. If the ankle joint can be dorsiflexed more than 10° when the knee is flexed, but not more than 10° when the knee is straightened, it indicates a contracture of the gastrocnemius muscle. If dorsiflexion of the ankle does not exceed 10° with or without knee extension and flexion, this indicates a contracture of the Achilles tendon. This test is also known as Silverskiold test. Treatment 1. Non-surgical treatment: gastrocnemius and Achilles tendon pulling exercises. Night splinting. Orthopedic shoes and braces. 2, surgical treatment: gastrocnemius lengthening. (1) Tibial nerve branch amputation. Suitable for spastic gastrocnemius contracture with clonus. (2) Proximal gastrocnemius lengthening. For spastic gastrocnemius contracture with fixed knee flexion deformity. (3) Distal gastrocnemius lengthening. For non-spastic gastrocnemius contracture