Key takeaways
- Many people have a "functional" leg-length difference from a twisted pelvis, which is not the same as legs that are truly different lengths.
- A true (anatomical) difference can add uneven wear to the lower back and hips over time.
- Clues include uneven shoe wear, one pant leg hemmed shorter, or a scoliosis.
- A quick screening exam tells whether a standing X-ray is needed; a simple shoe lift often helps.
Think of a car with one tire out of balance: it wears faster and unevenly. A leg-length difference can do something similar to your body. People with a true difference often start noticing lower back pain in their twenties or thirties, though it can show up later. It's often worse with long periods of standing, walking or running. Over the years, the uneven load may contribute to disc problems, arthritis and stenosis.
Could your legs be uneven? Ask yourself:
- Has anyone told me I have a scoliosis?
- Do I need one pant leg hemmed differently from the other?
- Do my shoes wear unevenly, in a different spot or faster on one side?
- When I bend forward, is one side of my back higher than the other?
- Are the creases under my buttocks uneven?
Functional vs. anatomical
Many people have what's called a functional leg-length difference. The legs are the same length, but a twisted or tilted pelvis makes one seem shorter. This is common, and it's often corrected with chiropractic care, stretching and posture changes.
An anatomical (true) difference means the bones themselves are different lengths. It can be present from birth or follow a fracture, a growth-plate injury, or a hip or knee replacement. This type may need a heel lift or shoe insert.
Why it's often missed
The traditional way of measuring leg length, with a tape measure from the hip bone to the ankle, crosses the hip and knee and is easily thrown off by posture and pelvic tilt. Small differences, which can still matter over time, are easy to miss this way.
The most accurate way to measure a true difference is a carefully positioned standing X-ray, barefoot, comparing the height of the hip joints.
Who should be checked?
- Anyone with recurring lower back, hip or knee pain, especially on one side
- Anyone with a scoliosis
- Anyone who has had a leg fracture, or a hip or knee replacement, particularly if back or leg pain began in the months after surgery
- Athletes, runners and people on their feet all day
Most people don't need an X-ray. A short screening exam looks at the level of your pelvis and hips and how your spine twists and turns. If a true difference is likely, a standing leg-length X-ray can confirm it. When one is found, a simple lift inside the shoe, which no one else can see, can take a lot of uneven stress off the spine.