The average mobility of the normal ankle joint is 48° of plantarflexion and 18° of dorsiflexion. When the knee joint is straight, the dorsiflexion of the ankle joint is ≤10°, which is called equinus foot deformity (equinus). The 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); and (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 the imbalance of the muscle strength of the foot, gait abnormality 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 respectively, 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 uncrossed 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. When the muscle is contracted, the foot is plantarflexed and the lower leg is flexed; when standing, the ankle joint is fixed and the body is prevented from leaning forward. 2.The flounder muscle is a broad and flat muscle, located on the deep side of the gastrocnemius muscle, starting from the head of the fibula and the upper part of the fibula, the medial edge of the tibia and the line of the flounder muscle. The muscle is a bicompartmental muscle that passes 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° to 150° depending on the individual. The cause of functional gastrocnemius contracture is not known. It may be related to its crossing of the knee and ankle joints. Sitting and lying positions reduce the tension of the gastrocnemius muscle and whether this makes it easier to shorten. Once a contracture of the gastrocnemius occurs, it may cause or be associated with the following pathologies: 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 can lead to inflammation or cartilage damage in the anterior aspect of the ankle. The anterior ankle bones form to reduce the pressure per unit area. 2, metatarsal tendonitis Because of the gastrocnemius contracture, the heel lift occurs earlier in gait, the dorsiflexion of the metatarsophalangeal joint tightens the metatarsal tendon membrane (winch mechanism), and the metatarsal tendon membrane is subjected to greater stress and is prone to tearing at the starting point. Among the 310 patients investigated in our outpatient clinic, 19 had metatarsal tendinitis, 14 of which (73.7%) also had gastrocnemius contracture and 1 (5.3%) had 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 heel valgus and puts more stress on the midfoot. In order to compensate for the shortened gastrocnemius tendon, hindfoot valgus, and midfoot rotation forward, maximum ankle dorsiflexion was achieved. 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. 4, bunion The excessive rotation of the midfoot forward causes excessive activity in the medial sequence of the foot. Rogers found that 58% of bunion patients had soft tissue clubfoot before surgery, and Mann and Coughlin noted that clubfoot may affect the long-term outcome of bunion surgery. A survey of 196 bunion patients at our institution found 115 cases (58.7%) with gastrocnemius contracture and 21 cases (10.7%) with combined Achilles tendon contracture. 4, 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 damage to the cartilage of the metatarsal head and osteoarthritis of the metatarsophalangeal joint. 5, diabetic foot ulcers Forefoot and midfoot stress increase makes the diabetic foot more prone to ulceration and rocker bottom deformity. Clinical examination The ankle joint is passively dorsiflexed in the extended and flexed knee joints, respectively. 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 contracture of the gastrocnemius muscle. If the dorsiflexion of the ankle does not exceed 10° with or without knee extension, 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 paroxysms. (2) Proximal gastrocnemius lengthening. Suitable for spastic gastrocnemius contracture with fixed knee flexion deformity. (3) Distal gastrocnemius lengthening. For non-spastic gastrocnemius contracture