Short Right Leg Syndrome Assessment - Structural Leg Length

 

On the totem pole of therapeutic occupations, I am pretty much at the bottom of the pole. However, I have spent much time since I was a boy measuring, cutting and assembling...eyeballing rooflines, gutters, posts and structures...measuring twice, cutting once to the fraction of a millimetre. I have studied mathematics and physics at both secondary and tertiary level achieving the distinction of a 98.3 Tertiary Entrance Ranking in this country. The human body is tricky and does hide things but the fundamental issue of structural leg length discrepancy in the vast majority of the population is undeniable. I am totally perplexed why it is not included in medical assessment protocols. Over a five year period suffering progressive lower limb deterioration following a lumbro-sacral injury, I was examined and treated by nine medico's and therapists. Not one examined structural leg length. This is typical.

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A common mistake examining leg length is confusing functional and structural differences. Examining a subject's relative ankle positions in supine on the treatment table reveals little about leg length. Should they be uneven, we are not able to make any statement about why there is a discrepancy without further examination. The difference could be due to distortion through the pelvis or torso pulling one side up...a functional difference...or it could be the leg's bones are different lengths...a structural difference. Measuring the length of a rod or length of timber can only be done measuring the distance between both ends. Determining which of two pieces is longer can be easily done lying them side by side and comparing the relative position of both ends. This gives an assessment of structural length.

 

The following tests and observations are indicative of comparative structural leg lengths and differentiate between low and high range cases. Together with confirming observations of Cardinal Signs and Signature Traits, comparative examination gives confidence a leg length discrepancy is present.

 

The most accurate measurement might be made by modern scanning technologies of bone length or x-ray of the hips in a frontal standing position. I have little experience with this. Chiropractic practice is to x-ray the pelvis and extrapolate an estimate of structural leg length from several measurements observed there. My observation of several cases left me unimpressed in that little care was taken to ensure good alignment of the subject when taking the x-ray. Slight sway to either side introduces large errors in the outcome. A measurement can be made with tape measure and square in standing position from floor to top of the Greater Trochanter against a wall or door frame. I have been able to make this measurement with an accuracy of +/-2mm. Where leg length discrepancies are typically in the range of 10mm and 20mm, this method taken into account with other confirming signs is sufficiently accurate for treatment purposes.

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I consider 10mm to 15mm to be lower range. Above 15mm is high range and will usually demonstrate greater symptomatic effects. Greater than 20mm is very high range. I have only sighted five cases at 25mm or above in ten years. Very low range cases, say less than 5mm, are uncommon. They still generate obvious Cardinal Signs but may be difficult to detect without scanning equipment. I have sighted one naturally short left leg case. The presentation of Cardinal signs was reversed and she carried her babies on the right hip.

 

​• Standing, viewed from the front, compare the subject's left and right ASIS. The left is typically 3mm to 10mm superior to the right. This may be difficult to observe for those with little experience in construction and assembly. This skill is learned through practice on the job. Cases with the higher number of 10mm are usually exception cases where the First Cardinal Sign of anterior rotation of the left hip has not occurred. Owing to the vagaries of hip rotation side to side, this observation is an indication only and not an accurate reflection of leg length discrepancy.

• Standing, viewed from the rear, the subject's right gluteal fold inferior to the left. I rarely use this observation...I would rather not go there in an initial consultation with a new client and it does not add to information gleaned from the other observations and tests described here.

• Supine, legs straight at the knees, compare the relative positions of the left and right malleolus and then the relative positions of the left and right Greater Trochanter pressing down superiorly to find their upper edge. The nett effect indicating comparative structural leg lengths...typically the ankles are essentially level with the right malleolus fractionally superior to the left (0.5-1mm) and a greater discrepancy at the pelvis with the left Greater Trochanter superior to right (10-20mm). These are typical observations, high range instance will exhibit differences greater than this. High range cases are not common.

 

•  Where the flesh about the hip is too thick to clearly identify the boney landmark at the Greater Trochanter, a fall back examination is comparing relative positions of the left and right ASIS in supine. This observation in supine will differ from the standing assessment due to the weight of the body pressing up through the Gluteal region does unwind anterior rotation at the left hip to some degree. This test is indicative of a structural leg length discrepancy but does not accurately reflect the magnitude unless it is an exception case with matching hip alignment in the Sagittal plane. Using the bony landmark at the Greater Trochanter is preferable to the ASIS because it eliminates the vagaries of hip rotation from examination.​

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•  Supine, raise knees forming a triangle with hip, knee and ankle, feet flat on table top. The object here is to compare the height of each triangle once setting the base of each to an equal length. Should one hip be superior (pelvic tilt Frontal plane) in the supine position, adjust the foot position of that leg superiorly by an equivalent amount and compare the height of the triangle at the knee's. Additionally, rotation through the torso/pelvis in the Transverse plane elevating one hip at the ASIS over the other and adjust to a level position. Thin bolstering might be best for this purpose.

 

•  Two observations can be made at the apex of the triangle at the knees. Firstly, the knee of the longer leg will may be higher by 5mm. Secondly, placing a line through the apex will indicate whether one knee is projecting further down the table. It is possible for the height at the apex to be even but one knee projects further down the table. A combination of elevation and projection down the table is possible. Where we know that at the hip, the left is elevated over the right and we are now adding to this projection down the table at the knee, it is clearly evident one leg is structurally longer than the other. Variations from case to case in terms of height at the apex or extension down the table are common due to variation in discrepancy between Femur and Tibia bones. This test confirms the straight leg comparison result and is also a concrete way of bringing it to the subject’s attention there is a leg length discrepancy...by raising their head slightly they have an ideal view of the bent knees. 

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•  Measurement of leg length can be made against the wall or door frame in standing position of distance from sole of foot to top of the Femur at the Greater Trochanter utilising a carpenter’s square and pencil to mark the height. I have been able to achieve an accuracy of +/-2mm. I do not normally attempt to do this in clinical practise. Perhaps I should do so but it adds to an already lengthy initial assessment and treatment session. It might be nice to know and may be necessary to convince a sceptical client. Comparative assessments described above suffice to confirm leg length discrepancy indicated by the presence of Cardinal Signs and determine whether it is a high or low range case.

 

​•  Evidence from frontal x-ray of the subject’s hips, standing upright gives questionable evidence. The slightest sway to the left or right away from centre significantly distorts relative heights and is really only useful if stance is centred. I have no experience attempting to use this method that is commonly employed by Chiropractors. I am aware of several cases where incorrect conclusions on structural leg length were made from this limited x-ray method. I have recently sighted full body x-ray images made at a Sydney hospital giving a full range of observations on structural and functional leg lengths, hip and spinal alignment which gives an outcome with great certainty.

 

•  Affecting a structural discrepancy might be functional knee, foot or ankle issues on one side adding or subtracting to the leg length discrepancy. A collapsed arch, flat footedness and a J'ing ankle are indicators will marginally reduce length. This is a functional component that has frequently been addressed with orthotic inserts prescribed by a Podiatrist or Physiotherapist. Leg length discrepancy is typically overlooked. In fact, I have sighted multiple cases where varying types of orthotics have been prescribed on one side only. Typically on the longer leg which more frequently experiences pain and dysfunction. The use of a single orthotic device adding a few millimeters height to the already longer leg can have catastrophic outcomes. 
 

•  Where structural leg lengths are near even and hip positions are level it is possible tightness and distortion through the torso can elevate one hip creating an equivalent discrepancy at the ankles. This functional parallelogram effect does not indicate a leg length discrepancy exists. In clinical practice, there is usually a combination of both functional and structural leg length discrepancies at play.