A patient demonstrates a right thoracolumbar scoliosis in standing but not in sitting. Which dysfunction is MOST likely the cause?

A patient demonstrates a right thoracolumbar scoliosis in standing but not in sitting. Which dysfunction is MOST likely the cause?

• A. Leg-length discrepancy
• B. Lumbar facet dysfunction
• C. Short iliopsoas muscle
• D. Unilaterally weak gluteus medius

Answer: (A)

A change in the spinal curve with posture points to a reversible, functional cause rather than a fixed structural issue. When standing, a right thoracolumbar curve appears because the pelvis tilts to compensate for a leg-length discrepancy; the shorter leg causes a pelvic obliquity, and the spine curves to keep the head level. In a seated position, the pelvis is supported and the obliquity is removed, so the spine realigns and the curve disappears. That pattern makes leg-length discrepancy the most likely contributor. Other options don’t fit as well. Lumbar facet dysfunction would produce localized pain and motion issues rather than a curve that fully resolves simply by sitting. A short iliopsoas can influence pelvic tilt and lumbar lordosis but doesn’t typically create a surgically reversible thoracolumbar scoliosis with a simple positional change. Unilateral gluteus medius weakness can cause pelvic drop during standing or walking, but the observed complete resolution of the scoliosis with sitting points more specifically to leg-length discrepancy as the cause.

A change in the spinal curve with posture points to a reversible, functional cause rather than a fixed structural issue. When standing, a right thoracolumbar curve appears because the pelvis tilts to compensate for a leg-length discrepancy; the shorter leg causes a pelvic obliquity, and the spine curves to keep the head level. In a seated position, the pelvis is supported and the obliquity is removed, so the spine realigns and the curve disappears. That pattern makes leg-length discrepancy the most likely contributor.

Other options don’t fit as well. Lumbar facet dysfunction would produce localized pain and motion issues rather than a curve that fully resolves simply by sitting. A short iliopsoas can influence pelvic tilt and lumbar lordosis but doesn’t typically create a surgically reversible thoracolumbar scoliosis with a simple positional change. Unilateral gluteus medius weakness can cause pelvic drop during standing or walking, but the observed complete resolution of the scoliosis with sitting points more specifically to leg-length discrepancy as the cause.