Human gait—the manner in which we walk—is a complex, coordinated activity involving multiple joints, muscles, and neurological inputs. In 1953, John Saunders, Verne Inman, and Howard Eberhart introduced the concept of the “six determinants of gait” to explain how the body minimizes energy expenditure and maintains stability during walking. These six biomechanical strategies help reduce vertical and lateral displacement of the center of gravity, making gait smoother, more efficient, and less taxing on the body.

1. Pelvic Rotation

Pelvic rotation refers to the movement of the pelvis in the transverse plane during walking. As one leg swings forward, the pelvis on that side rotates forward approximately 4 degrees, while the pelvis on the stance leg rotates backward by the same amount. This results in a total pelvic rotation of about 8 degrees.

The primary function of pelvic rotation is to lengthen the stride without requiring excessive hip flexion or extension. By rotating the pelvis, the body effectively increases the reach of the swinging leg, allowing for a longer step and smoother transition between strides. This motion also helps reduce the vertical displacement of the center of gravity by approximately 9.5 mm, contributing to energy conservation during gait.

2. Pelvic Tilt

Pelvic tilt, also known as pelvic drop, occurs in the frontal plane. During the stance phase of gait, the pelvis tilts downward on the side opposite the weight-bearing limb. This tilt averages around 5 degrees and helps lower the center of gravity during midstance.

The purpose of pelvic tilt is to reduce the vertical excursion of the body’s center of mass. Without this tilt, the center of gravity would rise significantly during midstance, increasing energy expenditure. By allowing the pelvis to drop slightly, the body maintains a smoother trajectory and avoids unnecessary vertical movement.

3. Knee Flexion During Stance Phase

Knee flexion immediately after heel strike is another critical determinant of gait. At heel strike, the knee is nearly fully extended. As the foot moves to a flat position on the ground, the knee flexes approximately 15 to 20 degrees. This flexion acts as a shock absorber, reducing the impact forces transmitted through the leg.

Biomechanically, knee flexion during stance helps lower the center of gravity and smooth the transition from heel strike to midstance. It also contributes to stability and reduces the risk of injury by dissipating ground reaction forces. Without this determinant, walking would be more jarring and less efficient.

4. Foot and Ankle Motion

The coordinated motion of the foot and ankle throughout the gait cycle plays a vital role in maintaining balance and propulsion. At heel strike, the foot is dorsiflexed, and the ankle joint is elevated. As the foot moves to a flat position, it plantarflexes, lowering the ankle joint. During push-off, the heel lifts, and the ankle joint rises again.

This cyclical motion of dorsiflexion and plantarflexion helps smooth the path of the center of gravity. It also facilitates shock absorption, stability, and forward propulsion. The ankle’s ability to adapt to different phases of gait ensures that the foot remains in optimal contact with the ground, enhancing efficiency.

5. Knee Motion During Swing Phase

Knee motion during the swing phase is essential for foot clearance and stride length. As the leg swings forward, the knee flexes to allow the foot to clear the ground. This prevents tripping and ensures a smooth transition into the next step.

The timing and degree of knee flexion are critical. Too little flexion can result in dragging the foot, while excessive flexion may disrupt balance. Proper knee motion also contributes to the overall coordination of the lower limb joints, working in harmony with the hip and ankle to maintain a fluid gait cycle.

6. Lateral Pelvic Displacement

Lateral pelvic displacement refers to the side-to-side movement of the pelvis during walking. As the body shifts weight from one leg to the other, the pelvis moves horizontally toward the stance leg. This shift helps position the center of gravity over the supporting foot, ensuring balance and stability.

Without lateral displacement, the body would be prone to tipping over the unsupported limb. This determinant is especially important for maintaining equilibrium during single-leg support phases. It also contributes to the characteristic side-to-side sway observed in normal walking.

Integration and Significance

Together, these six determinants of gait form a biomechanical framework that enhances walking efficiency. By minimizing vertical and lateral displacement of the center of gravity, the body conserves energy and reduces muscular effort. Each determinant plays a specific role in optimizing stride length, shock absorption, balance, and propulsion.

The concept of the “compass gait”—a hypothetical gait without these determinants—illustrates their importance. In a compass gait, the legs act as rigid levers hinged at the hips, resulting in exaggerated vertical movement and inefficient locomotion. The six determinants transform this rigid model into a dynamic, adaptive system that supports graceful and economical walking.

Clinical Relevance

Understanding the six determinants of gait is crucial in clinical settings, particularly in rehabilitation, orthopedics, and prosthetics. Deviations from normal gait patterns can indicate underlying musculoskeletal or neurological disorders. For example:

• Limited pelvic rotation may suggest hip stiffness or spinal rigidity.
• Abnormal pelvic tilt could be a sign of gluteal muscle weakness or Trendelenburg gait.
• Reduced knee flexion may result from joint pain, arthritis, or muscle weakness.
• Impaired ankle motion is common in stroke patients or those with peripheral neuropathy.
• Inadequate knee motion during swing can lead to foot drop or increased fall risk.
• Excessive or insufficient lateral pelvic displacement may reflect balance issues or compensatory strategies.

By analyzing these determinants, clinicians can develop targeted interventions to restore normal gait mechanics and improve patient outcomes.

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The six determinants of gait—pelvic rotation, pelvic tilt, knee flexion during stance, foot and ankle motion, knee motion during swing, and lateral pelvic displacement—are foundational to efficient human walking. They work in concert to reduce energy expenditure, maintain balance, and ensure smooth locomotion. Whether in biomechanics research or clinical practice, understanding these determinants provides valuable insights into the intricacies of human movement and the strategies our bodies employ to walk with grace and efficiency.

Foot orthotics are custom-designed devices used to support, align, or improve the function of the foot. Among the many modifications available in orthotic design, the cuboid notch stands out as a specialized feature aimed at addressing issues related to the lateral column of the foot. Though not universally applied, the cuboid notch has gained attention among clinicians for its potential to influence foot biomechanics, alleviate pain, and enhance gait efficiency.

What Is a Cuboid Notch?

A cuboid notch is a specific modification to a foot orthotic that targets the cuboid bone—a small, cube-shaped bone located on the lateral (outer) side of the foot, between the calcaneus (heel bone) and the fourth and fifth metatarsals. The notch can be either intrinsic (built into the orthotic shell during fabrication) or extrinsic (added as a pad or elevation made from materials like EVA, cork, or Poron adhered to the dorsal surface of the orthotic).

Traditionally, the cuboid notch was created by scooping out plaster under the cuboid area during the preparation of a positive model of the foot. With modern CAD/CAM systems, orthotic shells can be digitally designed to include an elevation under the cuboid, allowing for precise customization. Most orthotic labs accept prescriptions for cuboid notches in millimeters or fractions of an inch, depending on the desired degree of support.

Biomechanical Rationale

The cuboid notch is primarily used to support the lateral column of the foot, which includes the calcaneus, cuboid, and the fourth and fifth metatarsals. This area plays a crucial role in stability and propulsion during gait. By elevating the cuboid, the notch provides an upward force that resists plantar subluxation (downward displacement) of the cuboid, especially in conditions like cuboid syndrome or calcaneocuboid fault syndrome.

Additionally, the cuboid notch can facilitate medial movement of the center of pressure during midstance, aligning with Bojsen-Moller’s “high gear” propulsion concept. This biomechanical shift promotes more efficient push-off and can reduce lateral instability.

Clinical Applications

Though research on the cuboid notch is limited and lacks consensus, several clinical scenarios suggest its usefulness:

• Cuboid Syndrome: Characterized by pain and dysfunction in the cuboid region, often due to trauma or overuse. The cuboid notch helps stabilize the bone and prevent further subluxation.
• Calcaneocuboid Fault Syndrome: A condition involving misalignment or dysfunction at the calcaneocuboid joint. The notch offers targeted support to this joint, improving alignment and reducing discomfort.
• Lateral Column Collapse: Seen in flatfoot deformities or after trauma, where the lateral arch loses integrity. The cuboid notch helps restore the arch profile and redistribute load.
• Peroneal Tendon Dysfunction: By elevating the cuboid, the notch may enhance the mechanical advantage of the peroneus longus tendon, which stabilizes the first ray and supports lateral foot function.

Influence on Gait and Joint Mechanics

The cuboid notch can influence several aspects of foot and lower limb mechanics:

• Subtalar and Midtarsal Joint Motion: The notch introduces a pronatory moment, encouraging eversion and flexibility in these joints.
• Calcaneal Inclination Angle: Elevating the cuboid may indirectly raise the angle of the calcaneus, contributing to improved rearfoot alignment.
• Oblique Axis of the Midtarsal Joint: The notch helps pronate this axis, promoting plantarflexion of the fourth and fifth rays and enhancing lateral stability.

These biomechanical effects are particularly relevant in patients with rigid foot types, lateral instability, or those undergoing rehabilitation from lateral ankle sprains.

Design Considerations

Clinicians are more likely to prescribe a cuboid notch when using weightbearing or semi-weightbearing casting methods, as these techniques tend to flatten the lateral column. In traditional plaster-based manufacturing, the addition of plaster to the lateral column often lowers the arch profile, making the cuboid notch a corrective feature.

Prefabricated orthotics may also include a cuboid notch as part of their standard design, although customization remains preferable for optimal fit and function. The Feehery Modification is a variation where the notch is extended posteriorly to support the anterior lateral aspect of the calcaneus, offering broader lateral column support.

Potential Limitations and Risks

Despite its benefits, the cuboid notch is not universally suitable. In some cases, it may exacerbate symptoms, especially in individuals with hypersensitivity or pain around the cuboid region. Overcorrection or improper placement can lead to discomfort, altered gait, or new biomechanical issues.

Because there is no standardized protocol or robust clinical research validating its efficacy, the cuboid notch should be used judiciously and tailored to the patient’s specific anatomy and pathology. Regular follow-up and adjustments are essential to ensure therapeutic success.

The cuboid notch is a nuanced yet impactful modification in foot orthotic design. By targeting the cuboid bone and supporting the lateral column, it offers a biomechanical solution for a range of conditions—from cuboid syndrome to lateral instability and gait dysfunction. While its use requires clinical expertise and careful customization, the cuboid notch exemplifies how small design features in orthotics can yield significant improvements in foot function and patient comfort.

As orthotic technology continues to evolve, further research and clinical trials may help establish clearer guidelines for the use of cuboid notches, enhancing their role in evidence-based podiatric care.

Sources:
PodiaPaedia – Cuboid Notch
Podiatry FAQ – What is a Cuboid Notch?

The abductory twist is an observation which is found during an observation of the walking. Just as the heel starts to unweight or raise up the ground there’s a fast sudden abduction or twist seen of the heel. This is a commonplace finding during a gait evaluation, but its clinical value is of some discussion.

There are a number of reasons for an abductory twist. The first is that because rearfoot is pronating (rolling medially at the rearfoot) this is attempting to internally rotate the leg. Simultaneously the other leg is in the swing period moving forward and is wanting to externally turn the lower limb. The lower limb is ‘battling’ with these two opposite motions. Friction between the floor and the heel holds the heel from moving. The instant weight starts to come off the heel, the external rotation force from above can now abduct the rearfoot and it does so easily. A second explanation is that there is a condition at the great toe joint in which it fails to enable dorsiflexion correctly. This might be a hallux rigidus, a functional hallux limitus or a issue with the windlass mechanism that affects movement at the great toe joint. As this dorsiflexion is difficult to start, the body abducts the heel to maneuver sideways around that joint. Another reason which is often only found in the physical therapy literature is that the problem is as a result of control of motion around the hip joint. In that literature this is described as a medial heel whip.

The cause of debate about the clinical significance of an abductory twist is that it is merely an observation observed when doing a gait assessment that is the result of another thing (for example, the loss of friction with the ground, an issue at the big toe or hallux joint or the hip joint). If it is a problem, then therapy is directed at what is triggering the abductory twist or medial heel whip rather than aimed at the abductory twist itself. The treatment choices to do away with it is going to be very diverse dependent on what is the preferred treatment decision for what’s causing it.