A joint injury at twenty can become arthritis at fifty

A joint is where two or more bones meet — shoulders, elbows, hips, knees,
knuckles, and the spine. But a joint is more than bone:

Joint disorders are diseases or injuries affecting any of that, and they come
in three kinds.

1. Diseases

These usually cause pain and leave joints stiff, red or swollen, and most are
chronic — long-lasting, sometimes permanent.

• Arthritis. Many types; osteoarthritis is the most common. Over time
  it can cause severe joint damage, and it affects people of all ages. **A
  joint injury when you are young may cause osteoarthritis later in life** —
  which is the sentence that connects this section to the next one.
• Lupus. An autoimmune disease affecting many parts of the body, causing
  joint and muscle pain; some types often cause arthritis.
• Sjögren's syndrome. An autoimmune disease of the glands that make
  moisture. The main symptoms are dry eyes and mouth, and it often causes
  joint pain too.

Treatments differ by disease, but most include medicines and therapies to
relieve pain and other symptoms.

2. Sudden injuries

• Sprains — stretched or torn ligaments.
• Acute strains — stretched or torn muscles or tendons, from a sudden
  movement such as lifting something heavy.
• Dislocated joints — the bones pushed or pulled out of position. **A
  dislocation is a medical emergency.**

Many sports injuries can be treated at home. Call your provider if you
have a lot of joint pain, swelling or numbness; cannot put weight on the
joint; or have pain from an old injury with new swelling, instability, or
something else abnormal.

3. Overuse

Overuse injuries damage the joint's soft tissues, and happen when the same
movements are repeated too hard for too long — playing a musical instrument,
playing sport, or work such as carpentry or painting.

• Bursitis. The bursa is a small fluid-filled sac padding the bones of a
  joint from the muscles, tendons and skin around them. In bursitis it becomes
  irritated and swollen with extra fluid. Overuse is the most common cause;
  injuries, infections and arthritis can also cause it.
• Tendinitis. An overused tendon swells and makes the joint painful to
  move.
• Chronic strain. Muscles or tendons stretching or tearing **slowly over
  time** from repetition, rather than in one moment.

The treatments for all three are usually the same: **rest, keeping the injured
joint higher than your heart, and medicine to reduce swelling**, plus gentle
exercise. Sometimes an injection into the joint. If none of that helps,
surgery.

Keeping joints healthy

**Getting enough physical activity is one of the most important things you can
do** to prevent or slow joint disorders. It strengthens the muscles around a
joint, and stronger muscles make the joint work better — the protection is
indirect, which is why "rest the joint" is the wrong long-term instinct.

Wear the right protective equipment for your sport, such as knee pads. If you
already have joint problems, ask your provider which activities suit you.

*Source: National Institute of Arthritis and Musculoskeletal and Skin
Diseases, via MedlinePlus.*