Joints are easily damaged by injury, inflammation, and degeneration

Common Joint Injuries

Sprains and dislocations are the most common trauma-induced joint injuries, while cartilage injuries are especially problematic and common among athletes.

Cartilage Tears

Most commonly involve the knee menisci, but articular cartilage in other joints can also be damaged, especially in young athletes.

How Do Meniscus Tears Occur?

When a meniscus experiences compression and shear stress at the same time.

Why Do Cartilage Tears Rarely Heal on Their Own?

Cartilage is avascular (has no blood vessels), so it receives limited nourishment and usually cannot repair itself.

What Are the Consequences and Treatments of Cartilage Tears?

Torn cartilage fragments can cause a joint to lock or bind.

Damaged cartilage may be removed through arthroscopic surgery.

Partial meniscus removal reduces joint stability; complete removal increases the risk of early osteoarthritis.

A meniscal transplant may replace irreparably damaged cartilage in younger patients.

Sprain

An injury in which ligaments supporting a joint are stretched or torn. Common locations include the ankle, knee, and lumbar spine.

Why Do Sprains Heal Slowly?

Ligaments have a poor blood supply (are poorly vascularized), so partially torn ligaments repair slowly. Sprains are often painful and can limit movement.

What Are the Three Treatment Options for Completely Torn Ligaments?

Sewing the torn ends together (difficult because ligaments contain many fibrous strands).

Replacing with a graft, such as a piece of tendon (commonly used for the ACL).

Immobilization and time, which can work as well as surgery for some ligaments (such as the medial collateral ligament).

Dislocation

An injury in which bones are forced out of their normal alignment. It is often accompanied by sprains, inflammation, and difficulty moving the joint. Common locations include the jaw, shoulder, fingers, and thumbs.

How Are Dislocations Treated, and Why Can They Reoccur?

Reduction – A physician returns the displaced bones to their proper positions.

Subluxation – A partial dislocation of a joint.

Repeat dislocations occur because the initial injury stretches the joint capsule and ligaments, leaving the joint less stable.

Bursitis

Definition: Inflammation of a bursa, usually caused by a direct blow or friction.

Examples:

Housemaid’s knee (water on the knee): Inflammation of the prepatellar bursa from falling on the knee.

Student’s elbow (olecranon bursitis): Inflammation of the bursa near the olecranon from prolonged leaning on the elbow.

Treatment: Anti-inflammatory injections; needle aspiration can remove excess fluid and relieve pressure.

Tendonitis

Definition: Inflammation of tendon sheaths, typically caused by overuse.

Symptoms and treatment: Similar to bursitis.

Arthritis

Definition: A group of over 100 inflammatory or degenerative diseases that damage joints.

Common symptoms: Joint pain, stiffness, and swelling.

Acute arthritis: Usually caused by bacterial infection and treated with antibiotics.

Chronic arthritis: Includes osteoarthritis, rheumatoid arthritis, and gouty arthritis

Osteoarthritis (OA)

Definition: The most common type of chronic arthritis; a degenerative, “wear-and-tear” condition involving the breakdown of articular cartilage.

Most common in older adults, more often affects females, and is associated with aging.

What Happens to the Joints in Osteoarthritis?

Joint use and years of compression and friction can trigger enzymes that break down articular cartilage.

In OA, cartilage is destroyed faster than it can be replaced.

Cartilage becomes softened, rough, pitted, and eroded.

Exposed bone thickens and forms osteophytes (bony spurs), which enlarge bone ends and restrict movement.

Poorly aligned or overworked joints are at greater risk.

What Are the Symptoms and Commonly Affected Joints in Osteoarthritis?

Stiffness upon waking that improves somewhat with activity.

Crepitus: A crunching or grinding noise as rough joint surfaces rub together.

Commonly affects the cervical and lumbar spine, fingers, knuckles, knees, and hips.

How Does Osteoarthritis Progress, and How Is It Treated?

Usually slow-progressing and irreversible.

Symptoms may be managed with mild pain relievers, such as aspirin or acetaminophen, and moderate activity to maintain joint movement.

Can become disabling, especially when the hips or knees are affected.

What Are the Characteristics of Rheumatoid Arthritis (RA)?

Definition: A chronic inflammatory disorder that can occur at any age, but usually begins between ages 30 and 50.

Affects 3 times as many females as males and about 1% of the population.

Causes tenderness and stiffness, often affecting several joints bilaterally (on both sides of the body).

Commonly affects the small joints of the fingers, wrists, ankles, and feet.

Has flare-ups and remissions; may also cause anemia, osteoporosis, muscle weakness, and cardiovascular problems.

What Causes Rheumatoid Arthritis?

RA is an autoimmune disease, meaning the immune system attacks the body's own tissues.

The initial trigger is unknown; bacteria and viruses are suspected.

The immune system may mistake molecules in the joints for foreign substances and attack them.

How Does Rheumatoid Arthritis Damage the Joints?

Inflammation begins in the synovial membrane.

Inflammatory cells and chemicals enter the joint and cause tissue damage.

Synovial fluid accumulates, causing swelling.

The synovial membrane thickens into a pannus, abnormal tissue that attaches to and erodes articular cartilage.

Scar tissue forms between the bone ends and may eventually ossify (turn into bone).

What Is Ankylosis?

Ankylosis: The fusion of bone ends after scar tissue between them ossifies.

Immobilizes the joint and can cause bent, deformed fingers.

Not all RA cases reach this stage, but all involve restricted movement and significant pain.

How Is Rheumatoid Arthritis Treated?

Anti-inflammatory drugs: Steroidal and nonsteroidal medications reduce pain and inflammation.

Immunosuppressants: Slow the immune system's autoimmune reaction.

Biologic agents: Block inflammatory chemicals, including tumor necrosis factor (TNF).

These treatments can greatly slow joint destruction.

Joint replacement: May restore function in severe cases.

What Causes Gouty Arthritis, and What Are Its Symptoms?

Definition: A form of arthritis caused by urate crystals depositing in joint tissues.

Cause: Excess uric acid in the blood due to overproduction or slow excretion.

Uric acid is a normal waste product of nucleic acid metabolism.

Needle-shaped urate crystals trigger inflammation and extremely painful attacks.

The first attack usually affects one joint, commonly the base of the great toe.

What Are the Risk Factors, Complications, and Treatments for Gout?

More common in males, who generally have higher uric acid levels.

Genetic factors are involved; gout can run in families.

Untreated gout: Can cause bone ends to fuse, immobilizing the joint.

Treatment and prevention: Medications can stop or prevent attacks; drink plenty of water and avoid excessive alcohol and purine-rich foods (such as liver, kidneys, and sardines).

Lyme Disease

Cause: An inflammatory disease caused by spirochete bacteria transmitted through bites from infected ticks.

Symptoms: Joint pain and arthritis (especially in the knees), skin rash, flu-like symptoms, and foggy thinking.

If untreated: May cause neurological disorders and irregular heartbeat.

Diagnosis: Difficult because symptoms vary between individuals.

Treatment: Antibiotics, which work best when started soon after infection.

How Do Joints Develop and Change With Age?

Joints develop alongside bones from embryonic mesenchyme.

By week 8, synovial joints resemble adult joints, and synovial fluid is being secreted.

During childhood, joint size, shape, and flexibility change with use. Active joints develop thicker capsules and ligaments and larger bony supports.

With aging, ligaments and tendons shorten and weaken, intervertebral discs become more likely to herniate, and osteoarthritis becomes more common.

Rheumatoid arthritis also becomes more common during middle age.

How Can Exercise Help Prevent Age-Related Joint Problems?

Regular, moderate exercise through the joints' full range of motion (stretching and aerobics) helps:

Maintain ligament and tendon flexibility.

Keep cartilage nourished.

Strengthen muscles that stabilize joints.

Excessive or abusive joint use can promote early osteoarthritis.

Swimming and pool exercises reduce stress on weight-bearing joints because of water's buoyancy.

Preventing joint problems is easier than correcting them later.