A strict anatomical definition of leg length (LL) is the length of the femur + tibia. Due to the bipedal nature of the human species, “leg length” often is measured as: (femur + tibia + the height of the foot, from the tibia-talus articulation to the ground). Alternatively, the phrase “lower limb length” may be use to denote this linear dimension. In this paper, we use “leg length” to denote any of the measurements described below in section 3. We do so because in a living human being it is difficult to measure anatomical LL. The maximum length of the femur is measured from its head, at the proximal end, to its medial condyle, at the distal end. In life, the femur and pelvic bones overlap and the head of the femur is difficult to assess due to its articulation within the acetabulum. A high degree of body fatness may make these bony landmarks difficult, or, impossible, to access. Consequently, LL is often defined by an easier to measure dimension such as iliac height (IH) and subischial leg length (SLL). It is also possible to measure an estimate LL via the combination of thigh length (TL) and knee height (KH). Some studies employ only one of these measures as the indicator of LL.
Each of these measurements can be transformed in ratios, generally in relation to total stature and sitting height (SH) to give indications of body proportions. In this article we discuss the sitting height ratio (SHR), relative subischial leg length (RSLL), and the knee height ratio (KHR).