Lower Extremity: Definition and Anatomy

You lower extremity is a combination of parts:

• hip
• thigh
• knee
• leg
• ankle
• foot
• toes

There are over 30 bones in each of your lower extremities including:

Hip

• innominate (hip bone or pelvic bone)

Upper leg

• femur (thigh bone)
• patella (kneecap)

Lower leg

• tibia (shin bone)
• fibula (calf bone)

Midfoot/rearfoot

• tarsals, including:
  • talus (ankle bone), calcaneus (heel bone)
  • cuboid
  • navicular
  • medial cuneiform
  • intermediate cuneiform
  • lateral cuneiform

Forefoot

• metatarsals: although located in the middle of the foot, they’re typically considered part of the forefoot
• phalanges (toes): each toe has three bones except the big toe, which has two

The muscles in your lower extremity contract and relax to move skeletal bones and thus the body. Each of your lower extremities has more than 40 muscles.

Hip

There are 17 hip muscles, which can be sorted into four main groups:

• Gluteal muscles. These muscles help you stay upright and raise your thigh to the side, thrust your hips forward, and rotate your leg. This group includes the gluteus maximus (buttocks), gluteus minimus, gluteus medius, and the tensor fasciae latae.
• Abductor muscles. These muscles help you move the thighs together. This group includes the adductor brevis, adductor longus, adductor magnus, pectineus, and the gracilis.
• Iliopsoas muscles. The iliacus and psoas major help you flex your hips (bring your thighs to your abdomen).
• Lateral rotator muscles. This muscle group helps you move your thighs apart. The lateral rotator muscles include the externus and internus obturators, the piriformis, the superior and inferior gemelli, and the quadratus femoris.

Upper leg

The quadriceps include four muscles in the front of the leg that help extend the leg straight:

• vastus lateralis: on the outside of the thigh
• vastus medialis: on the inside of the thigh
• vastus intermedius: between the vastus lateralis and the vastus medialis
• rectus femoris: muscle attaches to the kneecap

The hamstrings include three muscles in the back that extend the thigh and flex the knee:

• biceps femoris
• semimembranosus
• semitendinosus

Lower leg

The calf muscles include three muscles that are critical for ankle, foot and toe movement:

• gastrocnemius: flexes and extends the foot, ankle, and knee
• soleus: important in walking and standing
• plantaris: acts with the gastrocnemius
• popliteus: initiates knee flexion/bending

Foot

Of the 20 muscles in each foot, the main ones are:

• tibialis anterior: moves foot move upward
• tibialis posterior: supports the arch and flexes the foot
• peroneals: move ankle and foot laterally
• extensors: raise toes at ankles for stepping forward
• flexors: stabilize toes against the ground

Your lower extremities are a complex combination of ligaments, tendons, muscles, bone, blood vessels, nerves, and more. Some important components of your lower extremities include:

Achilles tendon

Your Achilles tendon — the largest tendon in the body — connects the muscles in the back of your calf to your heel bone. When your calf muscle flexes, the Achilles tendon pulls on your heel so you can stand, walk, or run on your toes.

Femoral artery

Your femoral artery is the main arterial blood supply to your leg. It’s located in the front of your thigh.

Sciatic nerve

Your sciatic nerve branches from your lower back, through your hips and backside, and down each leg.

You might call the area between your hip and toes your leg, but a medical professional will call it your lower extremity, considering your leg as the area between your knee and your ankle.