Human Joints Explained

A Joint is Where Two Bones Come Together

Knee with rheumatoid arthritis
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Human joints are when ends of two bones come together. The joints hold them together and allow for movement of your skeleton.

Most of our joints are synovial joints and contain synovial fluid as lubrication. Muscles and ligaments provide movement and stability. All of the bones, except the hyoid bone in the neck, form a joint.

How Are Joints Categorized?

Joints are commonly categorized according to the motion associated with them.

Some of the joints are fixed, like those in the skull, allowing for no movement. Other joints, like those between the vertebrae of the spine, allow for some movement. Most of our joints are free-moving synovial joints.

The Two Main Types of Arthritis

There are two main types of arthritis, degenerative arthritis (e.g., osteoarthritis) and inflammatory arthritis (e.g., rheumatoid arthritis). When you have  osteoarthritis, the most common form of arthritis, the protective cartilage that covers the ends of the bones in a joint wears down over a period of years. Although osteoarthritis can affect any joint, it is most common in the knees, hips, hands, and spine.

Rheumatoid arthritis, by contrast, is an autoimmune disease and an inflammatory type of arthritis. The immune system goes awry and attacks the body's own tissues. It can develop at any age. Rheumatoid arthritis can also affect any joint in your body but typically involves your wrists, knuckles, and the middle joints of your fingers.

Gout is another example of inflammatory arthritis. Gout is actually more prevalent  than rheumatoid arthritis.

Common Joints Affected by Arthritis and Joint Pain

You have joints from your neck to your toes and arthritis can strike any of them. Here is the description of joints commonly affected by arthritis and pain.

  • Ball and Socket Joint: This type of joint allows for a wide range of rotation and movement. The shoulder and hip are ball and socket joints.
  • Condyloid Joint: This type of joint allows joystick-like movement but no rotation. There are condyloid joints in the jaw and fingers.
  • Gliding Joint: This type of joint allows bones to glide past each other. There are gliding joints in your ankles, wrists and spine.
  • Hinge Joint: This type of joint allows for movement much like that of a door hinge. The knee and ulna part of the elbow are hinge joints.
  • Pivot Joint: This type of joint allows bones to spin and twist around other bones. There are pivot joints in the neck and the radius part of the elbow.
  • Saddle Joint: This type of joint allows for back and forth and side to side motion but limited rotation. There is a saddle joint at the base of the thumb.

Improving the Health of Your Joints

There are a number of products available over-the-counter that promote better joint health. Can diet or dietary supplements really improve joint health?

Diet cannot cure arthritis. However, some studies have shown that there may be beneficial effects of fish oil supplementation, used as an adjunctive therapy in patients with rheumatoid arthritis. Fish oil is rich in omega-3 fatty acids which produce modest benefits and may reduce inflammation.

Sources:

Johns Hopkins Arthritis Center. Nutrition & Rheumatoid Arthritis. Cheryl Koch, CNSD. Updated by Rebecca Manno, MD, MHS 5/11/15.
http://www.hopkinsarthritis.org/patient-corner/disease-management/rheumatoid-arthrtis-nutrition/

Joint Index, Wheeless' Textbook of Orthopaedics. Last update 07/06/2011.
http://www.wheelessonline.com/ortho/joint_index

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