The subtalar joint is one of the three joints that make up the ankle joint and consists of four bones: the tibia, fibula, talus and calcaneus. According to SportsInjuryClinic.net, the subtalar joint is formed where the surfaces of the talus and calcaneus, or heel bone, come together. The function of the subtalar joint is to provide shock absorption and move the ankle in and out. It is part of the subtalar joint's normal function to pronate while walking or running.
Normal Walking
Subtalar joint pronation is meant to occur during normal walking and running in order to absorb the shock of the heel striking the ground. According to the University of Oklahoma Medical Sciences Center, during subtalar joint pronation, the calcaneus tilts to the outside, the talus moves upward and to the inside, while the tibia rotates to the inside and the knee flexes. The end result is that the foot rolls inward and the arch flattens during the gait cycle.
Distance Running
Some sports activities, such as running, can cause too much subtalar joint pronation, or overpronation. Overpronation can lead to overuse injuries and commonly affects runners, according to SportsInjuryClinic.net. Overpronation causes more stress on the inner side of the foot and increases the rotation of the ankle and knee. Repetitive forces, such as those that occur during running, cause extra stress to move up the shin to the knee, hip and back. Extra stress can cause injuries, including shin splints, Achilles tendinitis and knee pain. Custom-made arch supports called orthotics help reduce the amount of subtalar joint pronation.
Tight Achilles Tendon
A tight Achilles tendon can cause a condition called equinus. According to the Foot Health Facts website, equinus limits the upward movement of the ankle joint, making it difficult to bring the top of the foot up toward the shin. A common cause of equinus is a tight Achilles tendon, which can be the result of heredity or acquired due to inactivity or immobilization in a cast. Some women develop a tight Achilles tendon by wearing high heels too often. The subtalar joint compensates for a tight Achilles tendon by overpronating. Treatment includes stretching exercises, night splints and orthotics.
Muscle Spasms
Spasm of two calf muscles, the peroneus longus and peroneus brevis, can also cause excessive pronation at the subtalar joint, due to a condition called peroneal spastic flatfoot. According to Dr. Paula Lizak Gilchrist, a podiatrist practicing in Pittsburgh, Pennsylvania, the primary function of both muscles is to move the foot up and out during gait. When the muscles go into spasm, the foot does not relax back to a neutral position, causing the subtalar joint to remain pronated. Custom-made orthotics and strapping of the foot can help alleviate any pain or other symptoms, reducing pronation of the subtalar joint.
