Short Right Leg Syndrome Assessment - Structural Leg Length

 

Honestly, I am still a student of this topic. Do not expect full Osteopathic text book assessment protocols on the subject here. 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 things with great accuracy...eyeballing rooflines, gutters, posts and structures...measuring twice, cutting once to the fraction of a millimetre. 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.

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 very 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 upwards...a functional difference...or it could be bones of the pelvis and legs 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 but owing to compensating postural distortion through the pelvis do not accurately reflect precise structural leg length differences to the millimetre. Together with confirming observations of Cardinal Signs and Signature Traits, comparative examination gives confidence a leg length discrepancy is present.

 

The most accurate measurement is made by modern scanning technologies of bone length or x-ray of the hips in a frontal standing position. A less accurate 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. However, where acute symptoms are present and treatment is required, is it necessary to know the exact structural leg length difference? Choice of an adjusting heel lift thickness is not a function of leg length difference. There is no formula for determining the adjusting height. It is more a trial and error process to determine what amount the subject's body is prepared to accept to relieve stress through the pelvis. It is typically between 3 and 5mm. Realigning the body of a mature adult to a perfectly symmetrical state to level the hips and straighten the spine is not possible and attempting to do so would cause pain and injury.

• Standing, viewed from the front, subject's left ASIS superior to the right. This is typically in the 5 to 10mm range.


• 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 ASIS. The nett effect indicating comparative leg lengths...typically the ankles are essentially even with the right malleolus fractionally superior to the left (0.5-1mm) and a greater discrepancy at the pelvis with the left ASIS superior to right (10-20mm). These are typical observations, high range instance will exhibit differences greater than this. High range cases are not common. Owing to the presence of a unilateral anteriorly rotated left hip this test is only indicative of a structural leg length discrepancy but does not accurately reflect the magnitude.

• Supine, raise knees forming a triangle with hip, knee and ankle, feet flat on table top. Should one hip be superior 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...we want the base of each triangle to be the same length. The longer leg will typically be higher by 5 to 10mm. Where the left knee projects beyond the right knee inferiorly it is a sign the left femur is longer than the right. This is only viewable by the practitioner and hidden from the subject's view. Where the leg length difference is equally divided between the femur and tibia, there will be little or no inferior projection...the left kneecap simply stands tall over right. In low range cases it is often not easy to sight a significant difference. 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. Again, owing to compensating distortion through the pelvis, these observations are only indicative of a leg length discrepancy and do not accurately reflect the magnitude.

•  Crude measurements of leg length can be made against the wall or door frame 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 do not normally attempt to do this. It is difficult to do with accuracy and when I have attempted to do so, I would judge the accuracy to be not much better than +/-5mm. Where the leg length discrepancy is typically between 5 and 20mm, this degree of inaccuracy makes the measurement’s usefulness questionable...particularly in lower range cases and where determining the size of a corrective heel lift is not a function of the structural leg length difference. Comparative assessments of the legs side by side can be sufficiently revealing and useful. Nevertheless, use of a tape measure across the length of the bones without pelvic distortion confusing the issue can be reassuring.

• Frontal X-Ray of the subject’s hips, standing upright gives indisputable evidence measurable with great accuracy. 

 

•  Affecting a structural discrepancy might be functional foot and ankle issues of excessive pronation on one side adding or subtracting to the difference. A collapsed arch, flat footedness and a J'ing ankle are indicators. 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. It is possible there can be a combination of both functional effect and structural leg length difference at play.