As you can see, the correlation between LLI and chronic low back pain becomes demonstrable when LLI is above 15 mm.
In this study, Dr. Oro Friberg notes that relatively small amounts of LLI may only be clinically significant relative to conditions such as prolonged standing or gait, such as daily work, marathon runners, military training, and sporting activities.
In this study, Gofton and Trueman found a strong association between LLI and osteoarthritis (OA) on the side of the anatomically longer leg. I often explain it to my students in this way: The more extended leg hip joint gets impacted with increased load, as forces are pushing upwards, much as forces are pushing downward (with gravity) on the short leg side.
In their study, few subjects were aware of any difference in leg length. However, the authors acknowledge that many with LLI fail to develop this condition, suggesting that other factors may also be important.
LLI conclusion
In summary, childhood-onset leg-length inequality appears to have little clinical significance up to 20 mm. However, past the ~ 20 mm point, structural changes may cause compensatory muscular contractions.
The purpose of Knutson’s paper was to review the research regarding leg-length inequality, prevalence, mean magnitude or size, effects, and clinical significance.
The prevalence of leg length inequality seemed almost universal and was ninety percent of the population. However, the average magnitude of LLI was small and found to be 5.2 mm. Based on the research reviewed, small childhood-onset LLI under 20mm (under typical situations) does not seem clinically significant.
It seems the body is well able to compensate for minor LLI of up to 2cm. However, as a Posture Doctor who has spent years treating 100’s of people with LLI (including myself), I feel much more research is needed to convince me.
Until that time, I will continue to help those of you with LLI and your associated postural distortions; to bring your pelvis back towards a neutral orientation and decrease active muscular compensations through heel lifts, effective exercise programs, and manual treatment.
Further Resources: Scoliosis Exercises You Can Do From Home
