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Screening for Leg Length Discrepancy

Leg length discrepancy (LLD) is when there is a noticeable difference in length of one leg to the other. LLD is common and can be found in 70% of the population (Gurney, 2002). LLD can be structural or functional. Structural LLD is when a long bone in the leg is longer or shorter than the other. Structural LLD is often the result of congenital or boney damage of epiphyseal plate. Functional is when there is an apparent LLD from higher in the chain such as scoliosis. Generally as pelvic floor therapists we are orthopedic based therapists. In physical therapy school we learned that a leg length discrepancy had to be >1 cm to be considered significant, and based off of recent research that is still the case. Research in the last few years has focused on whether LLD has an effect on age related changes with osteoarthritis, posture & gait, and pain. Physiopedia suggests differential diagnosis of sacroiliac dysfunction, scoliosis, low back pain, iliotibial band (ITB) syndrome, stress fractures, and pronation. It can often feel like a chicken or egg question.

In the clinic I typically screen for a leg length discrepancy during my initial evaluation. A LLD may be noticed upon observation of gait assessment, standing posture, or part of the pelvic obliquity screen in standing and then in supine.

During gait, a LLD will create bilaterteral gait impairments. Khamis et al did a systematic review of LLD and gait deviations in 2017. They narrowed the search down to 12 articles and found that LLD >1cm was significantly related to gait deviations. These deviations occurred bilaterally, and while initially compensations occurred in the sagittal plane, as the LLD increased so did the gait deviations, and then affected frontal planes of motion as well. Resende et al (2016) agrees that even mild LLD should not be overlooked. They found that the most likely gait deviations were also in the sagittal planes and consisted of rearfoot and ankle dorsiflexion and inversion, knee flexion and adduction, hip adduction and flexion, and pelvic trendelenburg.

The sagittal, or right/left plane, and frontal, or front/back, plane involvement is consistent with the differential diagnosis of sacroiliac dysfunction, low back pain, and pronation. Really, one could justify why a LLD could contribute to pain and dysfunction in most of the lower body. It is reasonable to think that these compensational moments in gait over a long period create boney changes in the lower extremities which may contribute to low back pain.

Clinically, a leg length discrepancy can be assessed directly with a tape measure or indirectly with a shoe lift. Badii (2014) found a higher interrater reliability with the indirect method of a shoe lift as opposed to measuring with a tape measure.

Rannisto et al (2019) looked at leg length discrepancy among meat cutters with low back pain. All participants had been working for 10 years and were greater than 35 years old. Participants needed to have a LLD of 5mm (5mm is 0.5 cm) or more and complain of low back pain of >2/10 on visual analog scale (VAS). They were all given insoles and randomized into 2 groups; the intervention group were given lifts to correct the LLD about 70%; for example a 10mm LLD was corrected to 3 mm. The LLD was measured with a laser ultrasound technique. Participants were followed for 12 months. The intervention group had improvement in low back pain intensity, sciatica intensity, and took less sick time. Possibly the most amazing part is that for those that wore the heel lift at work the compliance was good.

Leg length discrepancy can often be an underlying component contributing to complaints of pain and dysfunction. It may have more of an effect on the populations who stand or walk for most of their work, and I wonder as more people transition to standing desks if we will see more people come into the clinic with a previously undiagnosed LLD.

My biggest clinical pearls from this research is that:
- Heel lifts can be used to diagnose and then for treatment (yay! One less step of getting the tape measure out)
- The heel lift does not have to be perfect. Clinically, I will try a lift and have the person walk, and then we can make a team decision if this lift is enough and feels better
- The gait compensations are consistently adduction and internal rotation throughout the lower body chain. I will continue to work on the opposing muscle groups; lateral rotators, hip extensors and abductors.

Leg Length Discrepancy can be evaluated using various assessments. To learn orthopedic evaluative techniques for patients, consider joining Lila Abbate in her course Advanced Orthopedic Assessment for the Pelvic Health Therapist.

Maziar Badii, A Nicole Wade, David R Collins, Savvakis Nicolaou, B Jacek Kobza, Jacek A Kopec, Comparison of lifts versus tape measure in determining leg length discrepancy; Journal of Rheumatology 2014, 41 (8): 1689-94
Renan A. Resende, Renata N. Kirkwood, Kevin J. Deluzio, Silvia Cabral, Sérgio T. Fonseca. "Biomechanical strategies implemented to compensate for mild leg length discrepancy during gait" Gait & Posture, Volume 46, 2016; 147-153, https://doi.org/10.1016/j.gaitpost.2016.03.012
Sam Khamis, Eli Carmeli, Relationship and significance of gait deviations associated with limb length discrepancy: A systematic review, Gait & Posture, Volume 57, 2017, 115-123, https://doi.org/10.1016/j.gaitpost.2017.05.028
Burke Gurney, Leg length discrepancy, Gait & Posture, Volume 15, Issue 2, 2002, Pages 195-206, https://doi.org/10.1016/S0966-6362(01)00148-5.
Satu Rannisto, Annaleena Okuloff, Jukka Uitti, et al. Correction of leg-length discrepancy among meat cutters with low back pain: a randomized controlled trial. BMC Musculoskeletal Disorders. 2019;(1):1. doi:10.1186/s12891-019-2478-3.

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