Orthopedic injury is rarely one-dimensional.

When evaluating a patient for bracing or prosthetic intervention, clinicians often focus primarily on sagittal plane motion—flexion and extension of the joints. While this plane dominates normal locomotion, true limb stability depends on coordinated motion across three planes of movement.

Understanding how the sagittal, frontal, and transverse planes interact is critical when assessing orthopedic injury, evaluating orthotic candidacy, or designing a device intended to restore functional movement.

In many patients, returning a joint to completely normal biomechanics is not possible. In those cases, orthotic and prosthetic intervention focuses on functional optimization, prioritizing the most important planes of motion while managing unavoidable deficits in others.

Establishing a Common Vocabulary

Different disciplines—orthopedics, biomechanics, rehabilitation, and orthotics—often describe the same planes of motion using slightly different terminology.

For clarity, this article uses the following definitions when evaluating motion in veterinary patients:

Sagittal Plane (also called the Median Plane)
Viewed from the side of the patient.
Primary motion: flexion and extension.

Frontal Plane (also called the Dorsal or Coronal Plane)
Viewed from the front or rear of the patient.
Primary motions: abduction, adduction, varus, and valgus.

Transverse Plane (sometimes called the Horizontal Plane)
Viewed from a bird’s-eye or top-down perspective.
Primary motion: internal and external rotation.

Thinking about the limb from these three viewing angles helps clinicians identify multi-planar instability, which is extremely common in orthopedic disease.

Sagittal Plane: The Engine of Gait

The sagittal plane divides the body into left and right halves and represents movement forward and backward.

Clinically, this plane is evaluated when observing the patient from the side.

Most propulsion during walking and running occurs through sagittal plane movement of the major joints of the limb, including the:

• shoulder
• elbow
• carpus
• hip
• stifle
• tarsus

Because sagittal motion directly contributes to stride length and propulsion, restoring sagittal plane mechanics is often the primary goal of orthotic intervention.

Common sagittal plane injuries

Cranial cruciate ligament (CCL) rupture
Creates cranial tibial translation and abnormal stifle mechanics.

Achilles tendon rupture
Eliminates the tarsal extension moment and produces a plantigrade stance.

Flexor tendon injuries
Reduce digital flexion and push-off strength.

Distal limb amputation
Removes normal propulsion mechanics.

When sagittal plane motion is severely compromised, animals often experience shortened stride length, reduced propulsion, and increased loading of other limbs.

Frontal Plane: Limb Alignment and Stability

The frontal plane—also known as the coronal plane—divides the body into dorsal and ventral halves.

Clinically, this plane is evaluated when observing the patient from the front or from behind.

Motion in this plane occurs toward or away from the midline and includes:

• abduction
• adduction
• varus
• valgus

Although frontal plane movement is smaller during normal gait, it is critical for joint alignment and stability.

This plane becomes especially important during:

• turning
• uneven terrain
• jumping or landing
• lateral acceleration

Orthotic device design often focuses heavily on controlling frontal plane instability while allowing normal sagittal plane movement.

Common frontal plane injuries

Collateral ligament injury
Produces varus or valgus instability in joints such as the stifle, carpus, or tarsus.

Angular limb deformities
Examples include radius curvus and valgus or varus deformities.

Carpal hyperextension injuries
Loss of palmar ligament support allows abnormal joint collapse.

Growth plate injuries
May lead to progressive angular deformity during development.

Uncontrolled frontal plane instability often results in uneven joint loading and accelerated degenerative joint disease.

Transverse Plane: Rotational Control

The transverse plane—sometimes called the horizontal plane—divides the body into cranial and caudal halves.

Clinically, this plane can be visualized as a top-down or bird’s-eye view of the patient.

Movement in this plane occurs through rotation and includes:

• internal rotation
• external rotation

Although rotational movement is subtle during normal gait, it plays a major role in joint alignment and load distribution.

Rotational instability is often underappreciated during routine gait assessment but can significantly influence long-term joint health.

Common transverse plane injuries

Cranial cruciate ligament rupture
Produces internal tibial rotation in addition to sagittal instability.

Patellar luxation
Often associated with rotational malalignment of the femur or tibia.

Hip dysplasia
Creates abnormal rotational forces within the hip joint.

Neurologic injury
May produce abnormal rotational limb positioning during gait.

Orthotic designs may address rotational forces through cuff geometry, strap orientation, and trim line positioning.

Why Multi-Planar Motion Matters

Orthopedic injuries rarely affect only one plane of motion.

For example:

CCL rupture

• Sagittal: cranial tibial translation
• Transverse: internal tibial rotation
• Frontal: secondary valgus instability

Carpal hyperextension

• Sagittal collapse
• Frontal instability under load
• transverse rotational compensation

A device designed to address only one plane may leave residual instability, while overly rigid designs may restrict normal motion and create compensatory problems elsewhere.

The Goal: Functional Optimization

In many patients, restoring perfectly normal biomechanics is not possible.

This is particularly true in cases involving:

• chronic ligament rupture
• severe degenerative joint disease
• neurologic injury
• limb loss

Orthotic and prosthetic intervention therefore focuses on functional optimization, often by prioritizing control of specific planes of motion.

This may include:

• restoring sagittal plane propulsion
• stabilizing frontal plane instability
• limiting excessive rotational forces

The clinical goal is not perfect biomechanics, but stable, repeatable movement that allows the patient to move comfortably and safely.

Final Thoughts

Orthopedic injury rarely occurs in isolation within a single plane.

Effective treatment requires recognizing how sagittal, frontal, and transverse motion interact during gait.

When evaluating veterinary patients for orthotic or prosthetic intervention, clinicians should consider:

• which planes are compromised
• which planes must be preserved
• which planes must be controlled

Understanding these relationships allows clinicians to design or prescribe devices that support stable, efficient movement rather than simply restricting motion.