Structural vs Functional Leg Length Discrepancy

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Initial assessment in my practice includes examination of hip alignment and leg length. Where a leg length discrepancy is observed, I am often asked, “Can it be adjusted?” There seems to be the expectation anything can be fixed by a quick potion, pill or manipulation. It does not always work out that way. There are two types of discrepancy; Structural and Functional.

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Structural

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Structural discrepancy relates to bones and joints which can vary in length and shape. Limbs can be different lengths side to side. Sometimes it is readily visibly but more commonly it is a matter of a few millimetres and it escapes notice except under close examination. Range of motion through the joints can vary due to abnormal formation of the joint structure. I have observed a few cases of this affecting hip joints. Structural differences cannot be changed or adjusted except by surgical procedure or the use of prosthetic devices such as a heel lift under a short leg.

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Functional

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Functional differences are where the bones of the limbs equal in length but owing to soft tissue strain and distortion from loading factors, overuse or injury contorting posture, an apparent difference will be evident from side to side as the torso elevates or rotates hips, pelvis, shoulder and spine. Also too, postural issues at hip, knee and ankle can affect leg length, eg: where the arch of one foot collapses, pronating the foot, bending the ankle and functionally reducing height. Through soft tissue manipulation, stretching and exercise it is possible to resolve Functional anomalies realigning the structure to a normal position.

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Clinical Findings

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In clinical practice, most cases will have a combination of Structural and Functional discrepancies. Prominent in my practice are the effects from structural leg length discrepancy which is typically overlooked or disregarded by conventional practitioners.

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This is important...attending to the Structural often resolves associated Functional discrepancies.

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The majority of cases have a structurally short right leg with a discrepancy in the range of 10mm to 20mm. Cases of 15mm and above are considered to be high range and usually display greater symptomatic effect. Even or near even leg length and short left legs are rare. The magnitude of symptomatic response does not necessarily correlate to the magnitude of discrepancy...response can be high in the presence of low range discrepancy and vice versa. Every case is unique and there are other influencing factors.​

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Discussion

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Therapists will often glance a patient’s ankles on the treatment table, commenting on leg length and “adjust” a Functional discrepancy. Unless close examination of the situation at the hips is also included, this is really not particularly useful commentary and does not distinguish between Structural and Functional differences. One cannot assess leg length without making a direct comparison of the legs at both ends. The length of a pole cannot be measured by looking at only one end. The reality is that the majority of therapists assume leg length is even and that any discrepancy sighted is Functional in nature and is adjustable. It would seem they think glancing at the ankles is all it takes. This is sloppy procedure relying on an unproven assumption.

 

The fact is, we pretty much all have a structural leg length discrepancy. The majority of cases examined in supine on the treatment table do have ankles that are aligned and appear to have even leg length. We walk on flat ground. The ground does not move to accommodate a structural discrepancy. Look to the pelvis for permanent tilt and distortion.

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My theory is a structurally short right leg gave our prehistoric ancestors a greater chance of survival in their child rearing years. The mechanics of a short right leg enable the child to be more readily carried on the left hip freeing the strong right arm for work and defence. This was the most successful model and through evolutionary adaptation it has become a dominant genetic trait.

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As two legged creatures, the foundation of our torso at the pelvis is particularly sensitive to differences in structural leg length. In the prone position moving on all fours the spine readily accommodates leg length discrepancy through rotation about the axis of the spine. The spine has a natural Lordotic and Kyphotic curvature in the Sagittal plane. We do the dolphin kick well. However, diversions in the Frontal plane generating Scoliosis strain the structure when walking erect on two legs.

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Like the fundamentals of building design where a level foundation is necessary, it is the same at our pelvis. Variation in structural leg length results in a tilt at the pelvis that creates an imbalance affecting hip alignment, gait and the spine. Muscular holding strain and joint stress impacts comfort, mobility and internal health through biomechanical and energetic Qi flow effects. It is my observation, minor structural leg length discrepancies do have a big impact. While juveniles and young adults are less affected and flexibility through the pelvis is preventative in the longer term, it is common for adults ageing beyond the life expectancy of our prehistoric ancestors to gradually begin experiencing effects. It is a contributory factor to low back pain and Lumbar disk injury. Individuals working on their feet for extended periods are more affected.

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Little understood by conventional therapists is the principle of proximal energetic Qi flow block at hip or shoulder having a distal effect in the limb. Many cases of Repetitive Strain Injury in forearm and elbow, Carpal Tunnel in wrist and hand, Piriformis Syndrome and Sciatic pain, Hamstring and Calf dysfunction and injury and Plantar Fasciitis result. While structural leg length discrepancy does promote mild scoliosis through the Thoracic and contribute to upper limb symptoms on the side of convexity, it more strongly impacts lower limb symptoms.

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I describe this as Left Lower Limb and Right Lower Limb Mechanisms. The left side affected by the First Cardinal Sign of Short Right Leg Syndrome where the hip rotates anteriorly about the Sacro-Iliac Joint in the Sagittal plane functionally pulling up the longer leg to make us feel more comfortable. Binding the SIJ, energetic Qi flow down the backline of the left lower limb is blocked. A subtle thickening and tightening through the Glutes, Hamstrings, Calf and Plantar Fascia result. This can escalate under loading and other influencing factors into acute pain, dysfunction and injury at any point along this line. This is the primary cause for left hamstring injuries experienced in football and the pro tennis circuit. The running and lunging these athletes do loads the hamstring. Sprinters are affected more in the calf and Achilles. Less athletic cases experience Piriformis and/or Plantar Fascia symptoms and anything in between. I have encountered one case which experienced all of the above over a twenty year period until he was fitted with a 5mm adjusting lift under his short right leg. Six months later muscle tone returned to normal, and his gait, balance and vitality improved. Being in his 70's, response to treatment was prolonged.

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Similarly, symptoms along the back line of the right lower limb are generated by blocking energetic Qi flow at the lumbar spine and hip on the right side. The Second Cardinal Sign of SRLS of rigidity at the right hip and SIJ plus lumbar strain with a right sided focus generated by right leaning pelvic tilt have the same effect as binding the SIJ from hip rotation on the left hip.

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Right lower limb cases are less common than left sided cases but are more of a concern because integrity of the spine is in question. Right sided cases are more difficult to treat and response times are longer.

Kidney function comes into question because the Bladder meridian in its convoluted passage through the lumbro-sacral region is vulnerable to blocking in the presence of low back tightness, strain and injury. In TCM theory, the Bladder feeds the Kidneys energetically. Where it is blocked, Kidney deficiency symptoms result. These include anxiety, aching lower back, weak knees, dry mouth, constipation, lethargy and general lack of vitality. This is not considered disease and is not detected by medical blood testing. It is an energetic imbalance detected by TCM pulse, tongue, eye diagnosis and treatable with acupuncture and herbal medicine. Until the blockage at the lumbro-sacral region is cleared, TCM treatment outcomes for this condition are never more than partial and temporary.

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Acute Right Lower Limb cases can experience Bladder meridian pain in the hamstring, insertion of the Biceps Femoris tendon to the Fibula behind the knee, calf and lateral aspect of the heel. Thickening and tightening through the limb can be prominent and attempts to release with direct massage treatment are painful and ineffective. Clearing blockage at the Iliac Crest at the right hip and QL’s of the right Lumbar spine will give immediate relief to the backline of the lower limb. Discussion of treatment for this and SRLS is covered separately.