Subtalar Joint

Original Editor - Lucinda hampton

Top Contributors - Lucinda hampton, Vidya Acharya, Abbey Wright and Kim Jackson  

Introduction

Subtalar joint

The subtalar (ST) joint is an articulation between two of the tarsal bones in the foot, the talus and calcaneus. The joint is classed structurally as a synovial joint, and functionally as a plane synovial joint.

The ST joint allows the foot side-to-side (inversion/eversion), pivot to change directions, and stay balanced as we move across uneven terrain. Without this joint, a person would constantly roll their ankles when running, jumping, or walking.

Structure

Subtalar ligaments Superior view

The ST joint is multi-articular joint, with three articulated facets that provide a surface for the joint to glide:

1. The anterior subtalar joint : Allows joint to glide forward (anterior articulation)
2. The medial subtalar joint: Allows joint to glide side-to-side (eversion/inversion)
3. The posterior subtalar joint: Allows the to glide backward (posterior articulation)

Talus, seen from below

The talus and calcaneous bones are held in place by strong but flexible connective ligaments. The main ligament that attaches these bones is called the interosseous talocalcaneal ligament. Four other weaker ligaments provide the joint with added stability. The interosseous talocalcaneal ligament, acts to bind the talus and calcaneus together. It lies within the sinus tarsi (a small cavity between the talus and calcaneus), and is particularly strong; providing the majority of the ligamentous stability to the joint.

In between the calcaneus and talus is the synovial membrane. This tissue secretes fluid to lubricate the joint space, protecting the cartilage and bones from damage.

Movements

The ST joint is formed on an oblique axis and is the main site within the foot for generation of eversion and inversion movements. This movement is produced by the muscles of the lateral compartment of the leg and tibialis anterior muscle respectively. The subtalar joint has no role in plantar or dorsiflexion of the foot.

Function

Ankle and foot in Neutral and Over-pronation

The ST joint is key to many functional activities eg walking and running, and posture while performing these tasks. The mechanisms behind how the subtalar joint propels you us is very complex.

This ST joints primary movements involve supination, in which the foot rolls toward the body's midline, and pronation, in which the foot rolls away from the midline. Both of these movements require a combination of distinct actions.

• Pronation requires a combination of dorsiflexion, abduction, and eversion.
• Supination requires a combination of plantar flexion, adduction and inversion

Physiotherapy Relevance

The subtalar joint is essential for mobility, and as such is prone to wear and tear, trauma, and joint-specific disorders. Any damage done to the subtalar joint and surrounding soft tissues that support it may lead to pain, and foot deformity (often permanent), and affect gait and mobility. Conditions affecting this joint include the below:

Directly Joint Related

1. Juvenile Rheumatoid Arthritis: The subtalar joint is often the first joint affected
2. Osteoarthritis: Post traumatic eg post fracture
3. Rheumatoid arthritis: Primarily attacks joint tissues, often the ankle and foot

Disorders in which the subtalar joint is indirectly affected or affected as a result of another defect or injury to the foot or ankle. Include:

1. Pes cavus/Pes planus
2. Subtalar dislocation
3. Chronic Ankle Instability
4. Tarsal coalition