Unequal leg length

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Unequal leg length
Physiotherapy now, next stop - school (6301592477).jpg
A girl with a congenital, structural difference in leg lengths is walking in a clinic.
Classification and external resources
Specialty rheumatology
ICD-10 M21.7
ICD-9-CM 736.81, 755.30

Unequal leg length (also termed leg length inequality, LLI or leg length discrepancy, LLD) is where the legs are either different lengths or appear to be different lengths because of misalignment.


There are two main types of leg length inequalities:

  • Structural differences are caused by the legs themselves being measurably different in length, usually due to differences in the length of the femur in the thigh or the tibia and fibula bones in the lower leg. This may be a birth defect or it may occur after a broken leg, serious infection, or local damage to one of the growth plates in a leg.
  • The other, more common, type is seen when the legs themselves are the same length, but due to neuromuscular injuries in the pelvis or upper leg, one leg or hip is held higher and tighter than the other (hypertonicity in the musculature of the pelvis or leg). These unequally tightened muscles cause the legs to seem to be different lengths, even though careful measurement would show equal lengths of the actual leg. This is called leg length alignment asymmetry (LLAA) and can be seen while lying down.[1]


The most common treatment for discrepancies in leg length is the use of a simple heel lift, which can be placed within the shoe. In cases where the length discrepancy is moderate, an external build up to the shoe is usually more comfortable. In severe cases, surgery can be used to make the longer leg shorter (or impede its growth), and/or make the shorter leg longer.

Measurement challenges[edit]

Although prone "functional leg length" is a widely used chiropractic tool in their Activator technique, it is not a recognized anthropometric technique, since legs are usually of unequal length, and measurements in the prone position are not entirely valid estimates of standing X-ray differences.[2] Measurements in the standing position are far more reliable.[3] Another confounding factor is that simply moving the two legs held together and leaning them imperceptibly to one side or the other produces different results.[4]

Clinical measurement of leg length conventionally uses the distance from the anterior superior iliac spine to the medial malleolus.[5] Projectional radiographic measurements of leg length have two main variants:[6]

  • Teleroentgenogram, which projects the entirety of both legs at the same time.
  • Orthoroentgenogram, which takes separate images of the hip, knee and ankle.

On X-rays, the length of the lower limb can be measured from the proximal end of femoral head to the center of the plafond of the distal tibia.[7]

Effect on Menstrual pain[edit]

As unequal leg length may contribute to a tilted pelvis, this may contribute to lower back pain.[8]

A hypothesis is that the lower back pain caused by a tilted pelvis, easily may be mistaken for menstrual pain, as women with lower back pain experience increased pain during their periods.


  1. ^ Knutson G. A. (2005). "Anatomic and functional leg-length inequality: A review and recommendation for clinical decision-making. Part II, the functional or unloaded leg-length asymmetry". Chiropractic & Osteopathy. 13 (12). doi:10.1186/1746-1340-13-12. 
  2. ^ D W Rhodes, E R Mansfield, P A Bishop, J F Smith. The validity of the prone leg check as an estimate of standing leg length inequality measured by X-ray. J Manipulative Physiol Ther. ;18 (6):343-6
  3. ^ Hanada E, Kirby RL, Mitchell M, Swuste JM (Jul 2001). "Measuring leg-length discrepancy by the "iliac crest palpation and book correction" method: reliability and validity". Arch Phys Med Rehabil. 82 (7): 938–42. doi:10.1053/apmr.2001.22622. 
  4. ^ Keeping Your Spine In Line, Adjusting the Joints, and Video, Alan Alda, PBS, Scientific American Frontiers. Video discusses Activator technique and leg length
  5. ^ Page 305 in: M. Lynn Palmer, Marcia E. Epler, Marcia F. Epler (1998). Fundamentals of Musculoskeletal Assessment Techniques. Lippincott Williams & Wilkins. ISBN 9780781710077. 
  6. ^ Page 269 in: Dror Paley (2002). Principles of Deformity Correction, Volume 1. Springer Science & Business Media. ISBN 9783540416654. 
  7. ^ Sabharwal, Sanjeev; Zhao, Caixia; McKeon, John; Melaghari, Todd; Blacksin, Marcia; Wenekor, Cornelia (2007). "Reliability Analysis for Radiographic Measurement of Limb Length Discrepancy". Journal of Pediatric Orthopaedics. 27 (1): 46–50. doi:10.1097/01.bpo.0000242444.26929.9f. ISSN 0271-6798. 
  8. ^ Cooperstein R, Lew M (2009). "The relationship between pelvic torsion and anatomical leg length inequality: a review of the literature". J Chiropr Med. 8: 107–18. doi:10.1016/j.jcm.2009.06.001. PMC 2732247Freely accessible. PMID 19703666.