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The Complexity of the Hip Joint
The hip joint is one of the most important joints in the human body: It bears our body weight while we sit, stand, walk, or run. Fortunately, it is extremely flexible, and allows for a large range of motion — second only to the shoulder — while providing great stability.
Since the primary function of the hip joint is to bear your body's weight, four features of the joint increase its stability:
- The bones (the femur and the acetabulum) fit together solidly;
- The ligaments are strong and thick;
- The cartilage allows the joint to slide together smoothly; and
- The muscles, in conjunction with the ligaments, keep the joint together.
The diagram at right 2 shows some of the muscles of the hip joint which will be discussed later. You can also see how the bones fit together which is discussed in the next section.
The Bones of the Hip Joint
The hip is made up of just two bones:
- The femur (or femoral head); and
- The acetabulum (or hip socket).
The acetabulum forms a large cup that surrounds the ball of the upper thigh bone. Together, they make the joint very strong; this is referred to as a ball-and-socket-joint. The hip joint is also a synovial joint: the bones are surrounded by an articular capsule which is lined by a synovial membrane. As a ball-and-socket joint, as well as a synovial joint, the hip has a great deal of free motion.
Four Ligaments around the Hip Joint
The hip joint is reinforced by four ligaments: three are extracapsular (outside the articular capsule) and one is intracapsular (inside the articular capsule).
The three extracapsular ligaments are attached to the pelvis. All three strengthen the joint by preventing excessive range of movement and also become taut when the joint is extended in order to stabilize it. If we didn't have these ligaments, our legs would be like the legs of a rag doll 3 — constantly moving in awkward directions. The three extracapsular ligaments are:
The iliofemoral ligament is the strongest ligament in the human body and prevents excessive adduction and internal rotation of the hip.
The ischiofemoral ligament prevents medial (internal) rotation.
The pubofemoral ligament restricts abduction and internal rotation of the hip joint.
The intracapsular ligament is named ligamentum teres. It is attached to depressions in the acetabulum and on the femoral head. It is only stretched when the hip is dislocated and its primary job is to prevent further damage.
Muscles of the Hip Joint
Thick muscles surround the hip at the back (the buttocks) and by the thigh in the front. They fall into four categories:
- Gluteal group: includes the gluteus maximus, gluteus medius, gluteus minimus, and tensor fasciae latae. (See diagram at left below.) See also: The Glutes.
Adductor group: includes the adductor brevis, adductor longus, adductor magnus, pectineus, and gracilis. See also: The Adductors.
Iliopsoas group: includes the iliacus and psoas major. The two muscles together are referred to as the iliopsoas. (Refer to the diagram at the beginning of this article.) See also: The Hip Flexors
Lateral rotator group: consists of the externus and internus obturators, the piriformis, the superior and inferior gemelli, and the quadratus femoris. (See diagram at right above.)
The hip muscles provide movement of the hip joint in several directions: flexion and extension, lateral and medial rotation, and abduction and adduction. (To refresh your memory on the meaning of these terms, see Planes of Movement or Dictionary of Common Fitness Terms).
Cartilage of the Hip Joint
Articular cartilage covers the femoral head and the inside of the acetabulum. In some places, it is almost 1/4 of an inch. It is very tough and very slick which allows the surfaces to slide easily against each other.
What can go wrong?
When you and your bones are healthy, not much can go wrong with your hip. But we often injure our hip while doing activities. Unfortunately, you can strain, dislocate or fracture your hip bones.
Certain diseases can also weaken the hip joint, the two most common being osteoarthritis and osteoporosis. (See also: Exercise and Osteoporosis, and Exercise and Arthritis.
Treatment for hip problems obviously varies with the individual situation. For instance, a dislocated or broken hip needs immediate medical treatment. Rest, medication, physiotherapy, surgery, or a complete hip replacement may be other solutions, depending on the condition and its severity.
Taking care of Your Hip Joints
First, you want to keep your bones strong. There are two things you can do:
Be sure calcium and Vitamin D are a part of your diet. Low-fat dairy foods, canned fish such as salmon, and dark-green leafy vegetables are good sources of calcium. Your body uses Vitamin D to absorb the calcium. That can be accomplished with a 15-minute exposure to the sun twice a week. You can also get Vitamin D from eggs, fish, and cereal. If you feel that you're not getting enough calcium and Vitamin D through your food or sunshine (especially during the winter months), you should consider a supplement. (Vitamin D, when taken with calcium, will help calcium to be properly absorbed by the body.)
Be physically active. Weight-bearing exercises are especially important for the hip joint: walking, jogging, and many sports, not to mention aerobics class. Simple squats are also good for you and your bones.
And there are two things you should try to control or talk to your doctor about:
Check your medications for side effects. Some medicines can make bones weaker. If you are taking any medications, talk to your doctor about their side effects. If they can cause your bones to be weaker, discuss how you can counter-balance that.
Stop smoking. People who smoke have an increased chance of breaking a bone. It's a habit worth breaking if you can. See your doctor for assistance.
Keeping your bones healthy is vital for an extended independent life. Talk to your doctor to be sure you are doing the right things.
I am a BCRPA-certified fitness instructor in Vancouver, BC. I teach four classes at the West End Community Centre in Vancouver, BC, mostly designed for the older adult. The Inevitable Disclaimer: Everything published here expresses only my opinion, based on my training and research. What you do with the information is entirely your own responsibility. I am not liable for any injury you suffer that seems to be related to anything you read here. Always consult your doctor before beginning an exercise program. For other articles, return to the table of contents.
These three dots behave exactly like a footnote. Click on them and you will get more information about the topic. ↩
Diagram from Wikipedia. ↩
One of the creepiest episodes of Criminal Minds used an "unsub" who captured people and removed their bones to turn them into human puppets. Honestly, I could not watch it! ↩