Intro to The Joint

We decided to get a little nerdy this month and explore THE JOINT. A joint is simply where 2 bones make contact in the skeletal system and allow movement of the human body. There are seven major joints in the body. Can you name all seven?

For purposes of trivia night or perhaps a crossword puzzle, bones are attached to one another by tissues called ligaments; muscles are attached to bones through tendons. Muscles stabilize joints. Muscle strength directly correlates with joint stability.

Joint Structure and Function

Joints are classified into 3 types: fibrous, cartilaginous, and synovial. Functionally, there are six types based on the type and degree of movement. These are:

• Ball and socket joint, example – shoulders
• Pivot joint, example – the neck
• Hinge joint, example – the knee
• Saddle joint, example – the thumb
• Condyloid joint, example – finger joints
• Plane joint or gliding joint, example – lower leg to ankle joint

Common Joint Disorders & Injuries

Osteoarthritis

Osteoarthritis is the most common joint disorder, developing from gradual cartilage damage and subsequent thinning. This condition is considered a “wear and tear” injury, more common in older than younger patients. Osteoarthritis is often seen with prior injury and long term high-impact stress on the affected joint. The degradation process itself does not cause pain; however, pain arises due to articular cartilage thinning, stimulating pain fibers in nearby areas. The joint's damage response is synovial fluid production, leading to swelling and inflammation that causes joint pain and stiffness. Compression of the underlying bone also results in pain, as bones are richly innervated.

Gout

Gout is an inflammatory arthritic condition arising from uric acid deposition within the joint resulting from overproduction or improper renal excretion and leads to uric acid precipitation within joints. The joint most affected is the big toe's metatarsophalangeal joint, a condition termed "podagra," and can also impact heels, ankles, finger, wrists, elbows, and knees. The pain in these joints can be excruciating.

Synovitis

Synovitis is inflammation of the synovial membrane that lines the synovial joints' articular capsules. Joint overuse is the most common cause of this condition in active, healthy people. Persistent synovitis in multiple joints may indicate rheumatoid arthritis, where the synovium is an autoimmune target. Rheumatoid arthritis can develop at any age and normally involves wrists, knuckles, and finger joints.

Sudden Injuries

Joint disorders can result from sudden injuries and include sprains and strains and dislocated joints. Sprains are stretched or torn ligaments. Strains are stretched or torn muscles or tendons. Dislocation is when a bone is pushed or pulled out of position and requires immediate medical attention.

Overuse

This can damage the soft tissue of the joint and results from working the joint too hard or doing the same thing over and over. Types of joint overuse injuries are: bursitis, tendinitis, and chronic strain.

Answer

The seven major joints in the body are: shoulders, hips, elbows, knees, wrists, ankles, and neck.

Extra credit: How many joints are typically in the human body? Please call the office if you need help with this one.