What is the Subtalar Joint?

Woman wearing ankle brace, low section. Credit: PhotoAlto/Odilon Dimier/GettyImages

The subtalar joint is a complex joint that is positioned below the ankle joint. The subtalar joint is comprised of the calcaneus (heel bone) and the talus, the bone that sits above it. The joint is actually three separate articulations between the two bones. It is also known as the talocalcaneal joint. When you sing, "the heel bone connected to the ankle bone" you are singing about the subtalar joint.

The main ligament of the subtalar joint is the inerosseous talocalcaneal ligament. Four more small ligaments connect the two bones, the anterior, posterior, lateral and medial talocalcaneal ligaments.

Three Functions of the Subtalar Joint

  • Adapting to changes in terrain while walking. This joint moves and tilts the foot inward or outward to adjust to the slope and uneven ground. It does not flex the foot up or down, only side to side.
  • Pivoting your body on your feet. You need the subtalar joint in order to twist your body while your foot remains planted on the ground.
  • Shock absorption as your feet hit the ground. The movement of the joint, bones and tendons takes the force of the impact of each stride.

When you twist your upper body while standing and look over your shoulder, the subtalar joints of your feet are moving along with your lower body. The two types of motion that the subtalar joint performs are supination and pronation.

Pronation is a natural motion that occurs as your foot's instep rolls inward, toward the middle of the body. As this happens, your arch collapses to a degree during pronation. Supination is motion in the opposite direction -- the foot rolls outward and the arch height increases. When you twist your body and look over your shoulder, one foot pronates and one foot supinates.

Problems Associated with the Subtalar Joint

  • Arthritis - Arthritis in the foot can be caused by excessive wear and tear on the subtalar joint over time or by a history of previous injury. A fracture of the talus or calcaneus may lead to arthritis pain in the foot.
  • Flat Feet - A subtalar joint that allows too much pronation can contribute to a flat foot.
  • Cavus Foot - Also known as a high arch foot, a cavus foot has a restricted range of motion at the subtalar joint, making it a more inflexible foot type.
  • Tarsal Coalition - A tarsal coalition is a fusion of bones that can cause restricted range of motion, pain, and a rigid flat foot.
  • Tarsal Tunnel Syndrome - This is a pinched nerve in the area of the subtalar joint that can cause shooting pain, burning, and tingling sensations.
  • When the subtalar joint produces pain, it is felt deeply within the joint and hard to locate. It might be felt at the outside of the ankle or the back of the ankle.
  • Subtalar arthroscopy may be used to remove scar tissue associated with bone and ligament injuries to the joint.

    Sources:

    Subtalar Arthroscopy, American Orthopaedic Foot & Ankle Society, accessed 11/19/15.

    Wheeless' Texbook of Orthopaedics, Duke Orthopaedics, Updated Dec. 6, 2013. Accessed 11/19/15.

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