Talocrural and subtalar joints - structure, movements; Plantar arches and X-ray Images

Introduction

The talocrural (ankle) joint and subtalar joint are critical components of the lower limb, enabling a wide range of movements necessary for ambulation and balance. Additionally, the plantar arches provide structural support for weight distribution and shock absorption during gait. This article reviews the anatomical structure, function, and radiological imaging of these elements.

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Talocrural Joint

Structure

The talocrural joint is a synovial hinge joint formed by the articulation between the distal ends of the tibia and fibula with the talus bone. The tibia and fibula create a mortise, into which the trochlea of the talus fits. This joint is reinforced by strong ligaments:

• Medial ligament (deltoid ligament): attaches the medial malleolus to the talus, calcaneus, and navicular bones.
• Lateral ligaments: include the anterior talofibular, posterior talofibular, and calcaneofibular ligaments, which prevent excessive inversion.

Movements

The talocrural joint allows for:

• Dorsiflexion (20 degrees): bringing the foot upwards.
• Plantarflexion (30-50 degrees): pointing the foot downwards.

Dorsiflexion is more stable due to the wider anterior trochlea of the talus fitting into the mortise.

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Subtalar Joint

Structure

The subtalar joint (talocalcaneal joint) is a synovial plane joint formed between the talus and calcaneus bones. It allows for gliding and rotational movements critical for foot inversion and eversion.

Movements

Movements at the subtalar joint include:

• Inversion (30 degrees): turning the sole medially.
• Eversion (10-20 degrees): turning the sole laterally.

These movements facilitate walking on uneven surfaces and contribute to foot pronation and supination.

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Plantar Arches

The plantar aspect of the foot comprises longitudinal (medial and lateral) and transverse arches, providing shock absorption and maintaining foot shape.

Support Structures:

• Medial longitudinal arch: supported by the spring ligament, plantar aponeurosis, tibialis anterior and posterior tendons.
• Lateral longitudinal arch: maintained by the long and short plantar ligaments, fibularis longus tendon.
• Transverse arch: supported by fibularis longus and tibialis posterior tendons.

Failure of these structures can lead to pes planus (flatfoot) or other deformities.

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Radiological Imaging

Standard radiographic evaluation of the ankle and foot includes:

• Anteroposterior (AP) view: assesses alignment of the tibia, fibula, and talus.
• Lateral view: visualizes the talocrural and subtalar joints.
• Oblique view: highlights midfoot and subtalar structures.

X-rays are crucial in diagnosing fractures, ligament injuries, and assessing joint integrity.

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Clinical Relevance

Injuries to the talocrural and subtalar joints are common, especially ankle sprains, fractures, and dislocations. Damage to supporting ligaments can compromise joint stability and arch integrity. Understanding the anatomy and biomechanics is essential for accurate diagnosis and treatment, including surgical repair or orthotic support in arch deformities.

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Conclusion

The talocrural and subtalar joints, along with the plantar arches, play a vital role in lower limb function by enabling complex movements while providing structural support. Radiographic imaging offers valuable insights into joint integrity, aiding in the management of acute injuries and chronic foot deformities.

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References

1. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. 8th ed. Philadelphia: Wolters Kluwer; 2018.
2. Gray’s Anatomy: The Anatomical Basis of Clinical Practice. 41st ed. Elsevier; 2016.
3. Netter FH. Atlas of Human Anatomy. 7th ed. Elsevier; 2019.