How does leg length discrepancy contribute to spinal pain and how is it assessed clinically?

• A. It is assessed by MRI
• B. It reduces spinal loading
• C. It can cause pelvic tilt and compensatory spine curvature; assess with standing alignment, palpation of bony landmarks, and block testing to quantify discrepancy
• D. It has no effect

Answer: (C)

When leg length discrepancy exists, the shorter leg causes the pelvis to tilt, which in turn creates a chain of compensations up the spine. The body tries to keep the head level and eyes forward, so the spine develops a compensatory curve or altered lumbar lordosis on the side opposite the tilt. Over time, this asymmetric loading stresses muscles, joints, and ligaments on one side, contributing to spinal pain.

Clinically, you assess this starting with standing alignment to see if the pelvis sits level or if one iliac crest or ASIS appears higher. Palpation of bony landmarks helps compare sides: ASIS, PSIS, iliac crest height, and the malleoli to detect height difference and pelvic tilt. To quantify the functional impact, you can use block testing: place a small block under the shorter leg and recheck pelvic level, spinal posture, and symptoms. If placing the block levels the pelvis and reduces pain or symptoms, that supports the role of leg length discrepancy in the patient’s spinal issue and helps estimate the discrepancy needed to achieve balance.

Imaging can provide precise measurements of leg lengths, but the described standing assessment, palpation, and block testing are the core clinical methods used to evaluate how LLD contributes to spinal pain.