Anatomy review: the subtalar joint

Written By Calibrate Pilates

The subtalar joint is a complex articulation that is often overlooked clinically, frequently ignored in favour of talocrural and midfoot mobility. But understanding the anatomy and mechanics of this joint can allow for better movement retraining through the foot, knee, hip, pelvis, and lumbar spine.

Anatomy review: the subtalar joint

  • The subtalar joint (STJ) is formed by the talocalcaneal (TC) and talocalcaneonavicular (TCN) articulations.

  • These 2 articulations have separate synovial sheaths. However, they don’t move independently and therefore function as a single joint —> allowing motion of the hindfoot in relation to the talus.

  • Anterior STJ = TCN articulation; middle STJ = interosseus tunnel (canalis + sinus tarsi); posterior STJ = TC articulation.

  • Ligamentous support is integral to the integrity of the subtalar joint, with no muscular attachments onto the talus.

Talocalcaneonavicular joint (anterior STJ)

  • Ball and socket articulation.

  • Calcaneus + navicular are connected by the spring
    ligament.

  • Superomedial ligament (part of the spring ligament)
    = medio-plantar sling for the talar head; closely
    related to deltoid ligament + tibialis posterior tendon.

  • The talonavicular portion of this joint also forms the
    functional midtarsal joint with the calcaeocuboid
    articulation.

Interosseous tunnel (middle STJ)

  • Intermediate root of inferior extensor retinaculum (IER) attaches here à winds around extensor digitorum longus tendons; lateral root of IER blends with the extensor digitorum brevis fascia.

  • Cervical ligament = covered by attachment of extensor digitorum brevis + lateral root of the IER; this is the strongest talocalcaneal attachment.

  • The tibial nerve, deep and superficial peroneal nerves lie within the tarsi.

  • The canalis and sinus tarsi ligaments are important for stability and range of motion of the subtalar joint.

  • The cervical ligament limits inversion.

  • The interosseous talocalcaneal and deltoid ligaments limit eversion.

Talocalcaneal joint (posterior STJ)

  • Planar articulation.

  • Posterior talocalcaneal ligament (absent in 15% of people) loops around the flexor hallucis longus tendon.

Biomechanics review: the subtalar joint

The subtalar joint has many axes of movement, depending on the phase of movement; it is a tri-planar joint.

  • The oblique axis of rotation primarily allows for inversion/eversion (frontal plane) + abduction/adduction (transverse plane) at the TCJ.

  • There is increased sagittal motion (dorsiflexion/plantarflexion) at the talonavicular portion of the TCNJ.

The STJ interacts closely with midtarsal joint (talonavicular + calcaneocuboid articulations).

  • When the STJ is inverted, its axis converges with MTJ —> limiting ROM of forefoot and midfoot —> foot becomes a rigid lever for propulsion.

  • When the STJ is everted, it is in parallel with the midtarsal join à allows more motion in the midfoot + forefoot for weight acceptance.

  • Functionally, pronation is a combination of dorsiflexion + eversion + abduction at the subtalar joint.

  • The STJ and forefoot cannot be supinated or pronated at the same time and be in a functional position for standing/weight transfer and gait.

Subtalar joint connections

  • Subtalar joint position critically influences gait.

  • Excessive valgus of the hindfoot/STJ → force vector that stresses medial soft tissue structures → decreased eversion ability → decreased stability through hindfoot.

  • Eversion of the calcaneus → talar adduction → tibial internal rotation → femoral internal rotation → pelvic nutation → lumbar spine extension (in a closed kinetic chain, i.e., gait).

Clinical Pilates in practice

  • The flexor hallucis longus, tibialis posterior, extensor digitorum longus, and extensor digitorum brevis are thus those muscles that we can work with to directly support the subtalar joint. Ensuring optimal length-tension relationships is key.

  • During footwork, do not over-work the extensor tendons, especially during “heels on bar” exercises.

  • Focus on grounding through the first ray and supporting the medial longitudinal arch to activate FHL + tibialis posterior support.

    → Prehensile footwork positions.

    → Parakeet.

  • Challenge subtalar joint mobility in closed- and open-kinetic chain positions.

  • Place straps/bars under rearfoot articulations, rather than on the heels, to challenge stability around the subtalar joint.

    → Leg Springs/Feet in Straps.

    → “Heels on bar” for Reformer/Wunda Chair/Cadillac Leg Press (supine/seated/standing).

  • To decompress and challenge strength around the tarsal tunnel, perform footwork in rearfoot neutral and add femora/tibial rotations.

    → Chastity/Pilates V positions moving from the hips and knees, but not the feet.

  • Maintain ankle and subtalar joint stability while performing open kinetic chain movements of the lower limb.

    → Scissors.

    → Bicycle.

    → One Leg Circle.

    → Side Kick Kneeling.

    → Control Balance, etc.

References

1. Bartoníček, J., Rammelt, S. and Naňka, O. (2018). Anatomy of the Subtalar Joint. Foot and Ankle Clinics, 23(3), pp.315-340.

2. Sangeorzan, A. and Sangeorzan, B. (2018). Subtalar Joint Biomechanics. Foot and Ankle Clinics, 23(3), pp.341-352.

3. Waerlop, I. and Allen, S. (2018). What do you know about pronation and supination? — The Gait Guys. [online] The Gait Guys. Available at: https://www.thegaitguys.com/thedailyblog/2018/8/7/what-do-you-know-about-pronation-and-supination?rq=subtalar%20joint

4. <a href='https://www.freepik.com/free-photos-vectors/technology'>Technology photo created by zirconicusso - www.freepik.com</a>

Calibrate Pilates
Previous

Clinical Review: Rheumatoid Arthritis