Hip: What to Know

Your hip joints are ball-and-socket joints positioned where your thigh bone meets your pelvis. The hip joint is involved in many types of movement. It is also one of the largest joints in the body, bearing nearly all of your weight. 

What Are Hips?

The scientific name for the hip joint is the acetabulofemoral joint. This joint permits a wide range of motion in your legs and helps with walking, squatting, jumping, going up and down stairs, sitting, and any other motion that involves raising or lowering your leg.

In general, ball-and-socket joints such as the hips have the most mobility out of any joint of the body.

What Do Hips Do?

This joint allows you to flex and extend your legs, rotate your legs in and out, and move your legs toward or away from your midline, although it doesn't only allow for a particularly large range of motion. It also serves to stabilize the connection between the upper and lower body.

Humans' unique pelvis and hip joints allow us to walk upright. As we evolved from quadrupeds (animals that walk on four feet) to bipeds (animals that walk on two feet) our pelvises and hip joints had to evolve, too. While walking upright is a significant advantage, our more narrow pelvis makes things like giving birth more difficult.

Where Are the Hips Located?

Hip anatomy is complex. The area is an intricate network of bones, cartilage, muscles, ligaments, tendons, and nerves.

Hip Bones. The bones of the hip consist of the top of the femur and the pelvis. Two sections of the pelvis are important to the hip joint. The acetabulum is the socket that the top of the femur fits into, and the sacrum supports the lower spine while serving as a connection point for many muscles and ligaments that also support the hips. 

Hip Muscles. The muscles of the hip help with motion and stabilization, and some do both. More than 15 muscles help your hips move, but the following are some of the largest and most important:

• Gluteus maximus: This connects at the ilium, the largest part of the pelvis, and at the sacrum. It helps you to extend and externally rotate your legs. It is important for getting up from a seated position, running, and walking uphill. It also provides support to the pelvis, helping you to do things like balancing on one leg.
• Gluteus medius: This is the primary muscle that helps with hip abduction (moving your leg away from your midline). It also helps to stabilize you when you need to temporarily balance on one leg while walking or running. It lies between the gluteus maximus and gluteus minimus.
• Gluteus minimus: This is the smallest glute muscle, and it is attached to the ilium. It helps with abduction but mostly works to stabilize your hips during such movements.
• Psoas major: This large and important muscle attaches to your spine on one end and the inner pelvis on the other. This muscle is complex and important. It connects the upper body and lower body and stabilizes that connection. It also connects the front of the body to the back. At the hip joint, the psoas helps you to raise and lower your leg, externally rotate your hip, and stabilize the hip when moving it to a minute degree.
• Iliacus: The iliacus connects the ilium of the pelvis and the sacrum. It helps with extending your leg and rotating it externally.
• Piriformis: This connects to the sacrum and helps you to lift your leg and rotate it. It is essential for shifting your weight from side to side while walking.

Hip Nerves. The nerves of the hip are important, supplying sensation to your legs and helping with walking and daily movement. They include the:

• Obturator nerve: Provides sensation for a portion of the thigh and motor input for several important hip muscles
• Genitofemoral nerve: Provides sensation to the genital area
• Lateral femoral cutaneous nerve: Provides sensation to the lateral thigh
• Femoral nerve: Provides sensation to portions of the leg and directs movement of the psoas and other important muscles
• Posterior femoral cutaneous nerve: Provides sensation to the back of your thigh
• Sciatic nerve: In some people, this nerve passes over the piriformis muscle. In others, it passes through the muscle. It is responsible for moving your hamstrings.