hindlimb

The hindlimb is the posterior limb of a tetrapod. In humans and other mammals it comprises the thigh, leg, and foot, extending from the hip to the toes. The main bones are the femur, patella, tibia, fibula, tarsals, metatarsals, and phalanges, organized into the thigh, leg, and foot.

Muscle groups act on the hindlimb to move and stabilize the leg: gluteal muscles and hip flexors in the thigh; the quadriceps and hamstrings span the knee; the gastrocnemius, soleus, and deep plantarflexors control the ankle and foot. Nerve supply is mainly via the sciatic nerve and its branches; arterial blood is delivered by the femoral and popliteal arteries, among others.

Function and locomotion: Hindlimbs bear weight, provide propulsion, and enable various gaits such as walking and running. In bipeds, they are the primary locomotor limbs, while in quadrupeds they work with the forelimbs to propel the body. Adaptations include the arching of the foot for energy storage and efficient push-off; limb length and joint angles vary with mode of locomotion. In birds and many other vertebrates, hindlimbs are adapted for locomotion on land or perching, with variations that reflect ecological demands.

Development and variation: In embryology, hindlimbs develop from hindlimb buds in the lateral plate mesoderm, patterned by signaling centers such as the apical ectodermal ridge and zone of polarizing activity. Across tetrapods, hindlimbs show a wide range of proportions and specializations related to locomotor strategy and habitat.