Functional Leg Length Discrepancy: A Whole-Body Physiotherapy Approach
Functional Leg Length Discrepancy (FLLD) occurs when both legs are structurally the same length, but one appears shorter due to postural or muscular imbalances. Unlike a structural discrepancy (where bone length differs), this is often the result of compensations from the pelvis, spine, or surrounding soft tissues.
What Causes FLLD?
Common contributors include:
Pelvic rotation or tilt
Muscle imbalances (tight hip flexors, weak glutes or abdominals)
Foot mechanics (pronation or supination)
Previous injuries or surgeries
Spinal or sacroiliac joint dysfunction
These asymmetries can lead to uneven weight distribution, gait changes, and overuse patterns throughout the body.
How Is It Identified?
FLLD is typically observed through:
Gait analysis and postural assessment
Supine-to-sit test
Functional movement screening
Palpation of pelvic landmarks and leg positioning
While radiographs are useful for structural discrepancies, they’re not the primary tool for functional cases.
When Is It Clinically Relevant?
Small differences (<1 cm) are common and often asymptomatic.
Larger or symptomatic discrepancies (>1.5–2 cm) may lead to pain, instability, or joint stress.
Even mild discrepancies can have a significant impact depending on activity level and compensation patterns.
Why It Matters
FLLD can create a ripple effect across the body:
Pelvis and Spine: Contribute to low back pain, SI joint irritation, or scoliosis
Hips and Knees: Uneven loading may accelerate joint wear
Foot and Ankle: Increased strain, especially on the "shorter" or more loaded side
Physiotherapy Management of FLLD
A tailored physiotherapy approach is the most effective way to address functional discrepancies:
1. Manual Therapy & Joint Rebalancing
Mobilize the sacroiliac joint or thoracolumbar spine if restricted
Release overactive muscles (e.g. quadratus lumborum, hip flexors, piriformis)
Normalize soft tissue tension between both sides
2. Corrective Exercise
Key focus areas:
Pelvic Stability: Glute medius, adductors, deep core
Foot Control: Intrinsic foot muscle activation and ankle stability
Postural Alignment: Spinal mobility, thoracic extension, and scapular positioning
Proprioception: Improve body awareness and symmetry through balance drills and unilateral exercises
Example exercises may include:
Glute bridges with banded abduction
Single-leg balance with hip correction cues
Step-downs or lunges focusing on symmetry
Core engagement with anti-rotation (e.g. Pallof press)
3. Gait & Movement Re-Education
Restore normal stride length and cadence
Teach symmetrical loading strategies during walking, lifting, or climbing stairs
Use mirrors, tactile feedback, or video to cue alignment and posture
Takeaway
Functional leg length discrepancy can quietly impact posture, movement, and long-term joint health. Left unaddressed, it may lead to chronic discomfort, uneven wear on joints, and compensatory patterns throughout the body.The encouraging news? It’s highly treatable through focused physiotherapy. By targeting the underlying issues, like pelvic alignment, muscular imbalances, and motor control, we can restore balance, enhance movement efficiency, and reduce pain. A personalized, progressive rehab plan makes all the difference in reclaiming symmetry and function.
References
Gurney B. (2002). Gait Posture
Knutson G. (2005). Chiropractic & Osteopathy
Friberg O. (1983). Spine
Khamis S, Carmeli E. (2017). Gait & Posture
