Ankle Movement: Understanding True Rotation, Pronation, and Supination

What is the internal and external rotation of the ankle?

True, isolated internal and external rotation of the ankle joint (talocrural joint) is extremely limited, with most "rotational" movements attributed to the combined motions of the foot (pronation and supination) or rotation occurring higher up the kinetic chain at the knee or hip.

Understanding Ankle Movement Terminology

The ankle joint complex is a marvel of biomechanical engineering, designed for both stability and adaptability. However, its terminology can often be a source of confusion, particularly when it comes to "rotation." To clarify, let's first define the primary movements of the ankle and foot:

• Dorsiflexion: Pointing the toes upwards, bringing the top of the foot closer to the shin.
• Plantarflexion: Pointing the toes downwards, extending the foot away from the shin.
• Inversion: Turning the sole of the foot inwards, towards the midline of the body.
• Eversion: Turning the sole of the foot outwards, away from the midline of the body.

While these terms describe the primary movements, the concepts of "internal" and "external" rotation, as understood in other joints like the hip or shoulder, do not directly apply to the ankle in the same way.

The Ankle Joint Complex: Limited True Rotation

The ankle is not a single joint but a complex of several articulations working in concert:

• Talocrural Joint: This is the main "ankle joint," formed by the tibia and fibula (the lower leg bones) and the talus (one of the foot bones). It functions primarily as a hinge joint, allowing for dorsiflexion and plantarflexion. While a minute amount of axial rotation (less than 5 degrees) can occur, it's not a primary or significant movement in isolation.
• Subtalar Joint: Located just below the talocrural joint, this articulation between the talus and calcaneus (heel bone) is crucial for inversion and eversion. These movements are not pure rotations but rather triplanar motions that involve components of adduction/abduction, plantarflexion/dorsiflexion, and slight rotation.
• Transverse Tarsal Joint: Comprising the talonavicular and calcaneocuboid joints, this joint works synergistically with the subtalar joint to allow for the foot's adaptability to uneven surfaces.

Given this anatomical setup, the idea of the foot truly "internally" or "externally rotating" at the ankle joint itself is largely inaccurate from a strict anatomical perspective.

"Internal Rotation" of the Ankle: A Functional Misnomer

When people refer to "internal rotation of the ankle," they are most commonly describing one of two scenarios:

1. Foot Pronation: This is the most frequent interpretation. Pronation is a complex, triplanar movement of the foot that involves:

   • Dorsiflexion (slight)
   • Eversion (outward turning of the sole)
   • Abduction (toes moving away from the midline) Pronation is often observed as the arch of the foot flattening and the foot rolling inward. Functionally, it allows the foot to become more flexible, adapting to uneven surfaces and absorbing shock during gait.

2. Internal Rotation of the Tibia/Leg: In some contexts, "internal rotation of the ankle" might refer to the internal rotation of the lower leg (tibia and fibula) at the knee joint. This rotation of the leg bones directly influences the orientation of the foot, making it appear as if the ankle is rotating inward. This is a crucial distinction, as the movement originates higher up the kinetic chain.

"External Rotation" of the Ankle: A Functional Misnomer

Similarly, "external rotation of the ankle" typically refers to:

1. Foot Supination: This is the opposite of pronation and is also a triplanar movement involving:

   • Plantarflexion (slight)
   • Inversion (inward turning of the sole)
   • Adduction (toes moving towards the midline) Supination is often observed as the arch of the foot heightening and the foot rolling outward. Functionally, it transforms the foot into a rigid lever, providing stability and power during push-off in activities like walking, running, and jumping.

2. External Rotation of the Tibia/Leg: This refers to the external rotation of the lower leg at the knee joint. Like internal rotation, this movement of the leg bones dictates the outward orientation of the foot, giving the impression of external ankle rotation.

Why the Confusion? The Kinetic Chain Perspective

The confusion surrounding "ankle rotation" stems from the interconnected nature of the human body. The foot and ankle complex functions as part of a larger kinetic chain involving the knee, hip, and even the spine. Movements at one joint inevitably influence the position and movement of joints above and below it.

When the lower leg internally or externally rotates at the knee, the foot, being attached to the tibia and fibula, will also rotate with it. This creates the visual effect of ankle rotation, even though the primary movement is occurring at the knee. Therefore, it's more accurate to discuss:

• Foot pronation/supination (movements within the foot itself).
• Tibial internal/external rotation (movements of the lower leg bones).

Functional Significance in Movement and Performance

Despite the anatomical nuances, the functional "rotational" movements of the foot (pronation and supination) and the lower leg are critical for:

• Gait Cycle: During walking and running, the foot naturally pronates upon initial contact to absorb shock and adapt to the ground, then supinates for a rigid push-off.
• Balance and Stability: The ability to pronate and supinate allows the foot to adjust to uneven terrain, maintaining balance.
• Sports Performance: Activities requiring quick changes of direction, pivoting, or powerful propulsion (e.g., basketball, soccer, running) heavily rely on controlled pronation and supination and efficient lower limb rotation.
• Shock Absorption: Controlled pronation dissipates forces throughout the lower limb, protecting joints higher up.

Clinical Implications and Assessment

Understanding these movements is crucial for healthcare professionals and fitness experts:

• Injury Risk: Excessive or uncontrolled pronation (overpronation) or supination (oversupination) can contribute to various lower extremity injuries, including:
  • Plantar fasciitis
  • Achilles tendinopathy
  • Shin splints
  • Patellofemoral pain syndrome (runner's knee)
  • IT band syndrome
• Assessment: Clinicians often assess foot posture (e.g., flat feet, high arches) and observe gait patterns to identify imbalances in pronation/supination. They may also assess tibial torsion, which is the amount of twist in the tibia bone itself, influencing foot alignment.
• Rehabilitation and Training: Interventions may focus on strengthening muscles that control foot movements (e.g., tibialis posterior for supination, fibularis muscles for pronation) or addressing rotational imbalances at the knee or hip to improve overall lower limb mechanics.

Conclusion

While the terms "internal rotation" and "external rotation" of the ankle are commonly used in casual conversation, it is important to understand that true, isolated axial rotation at the talocrural joint is minimal. Instead, these terms typically refer to the complex triplanar movements of the foot – pronation (often functionally akin to internal rotation) and supination (functionally akin to external rotation) – or the rotation of the lower leg (tibia) at the knee joint, which dictates the orientation of the entire foot. A precise understanding of these biomechanical distinctions is essential for accurate assessment, effective training, and injury prevention in the lower kinetic chain.