Structural Leg Length Tests Demonstrating SRLS
• Standing, viewed from the front, subject's left ASIS superior to the right.
• Standing, viewed from the rear, the subject's right gluteal fold inferior to the left.
• 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 an anteriorly rotated left hip this test is only indicative of a leg length difference but does not accurately reflect the magnitude.
• Supine, raise knees forming a triangle with hip, knee and ankle, feet flat on tabletop. 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. The longer leg will typically be higher by 5 to 10mm. Where the left ASIS is elevated above the right ASIS yet the left knee projects beyond the right knee inferiorly 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...left will simply stand tall over right kneecap. 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 difference...by simply raising their head slightly they have an ideal view of the knee height discrepancy.
• Frontal X-Ray of the subject’s hips, standing upright gives indisputable evidence measurable with great accuracy.
• Where structural leg lengths near even and hip positions level it is possible tightness and distortion through the torso can elevate one hip creating an equivalent discrepancy at the ankles. This parallelogram effect does not indicate a leg length difference exists. It is possible there can be a combination of both parallelogram effect and structural leg length difference at play.