Evolution of the human hip. Part 1: the osseous framework

Abstract

Extensive osseous adaptations of the lumbar spine, pelvis, hip and femur characterize the emergence of the human bipedal gait with its 'double extension' of the lumbar spine and hip. To accommodate lumbar lordosis, the pelvis was 'compacted', becoming wider and shorter, as compared with the non-human apes. The hip joint acquired a much more extended position, which can be seen in a broader evolutionary context of verticalization of limbs. When loaded in a predominantly vertical position, the femur can be built lighter and longer than when it is loaded more horizontally because bending moments are smaller. Extension of the hip joint together with elongation of the femur increases effective leg length, and hence stride length, which improves energy efficiency. At the hip joint itself, the shift of the hip's default working range to a more extended position influences concavity at the head-neck junction and femoral neck anteversion.

Figure 1.

Steps in verticalization of limbs, placing the limbs under the trunk. (A) Reptile, (B) non-cursorial mammal and (C) cursorial mammal, from [6].

Figure 2.

Double extension of the hip and spine: a vertical femur and lumbar lordosis (from [10]).

Figure 3.

A long femur indeed: anterior view of a femur of a rhinoceros (graviportal, left), human and giraffe (cursorial, right). Scale is identical for all three femora.

Figure 4.

The Ardipithecus pelvis at 4.4 mya was already more human- than chimpanzee-like. Three pelves in lateral (top row), anteroposterior and axial views (bottom row). From left to right: Chimpanzee (Pan troglodytes), Ardipithecus ramidus of 4.4 mya and Homo sapiens (A. ramidus adapted from [24], with permission).

Figure 5.

Concavity in non-human apes and humans. (A) gorilla, (C) chimpanzee, (C and D) human. The non-human apes uniformly have large concavity and more so anteriorly than posteriorly. Some humans (C) have only small concavity anteriorly, others have larger anterior concavity (d), but virtually all humans have large concavity posteriorly (C, D). View is perpendicular to the superior femoral neck, from [26], with permission.