This arthritis affects a joint at the top of your shoulder. It's where the shoulder blade's bony protrusion (called the "acromion") meets the clavicle. This joint acts as a pivot point when you raise your arm above your head.

This is a disease of the nervous system. The proper name is "amyotrophic lateral sclerosis," but most people know it as "ALS" or "Lou Gehrig's disease." With it, your nerve cells begin to break down and die. ALS is a progressive disease. That means its effects get worse over time. There is no cure. Eventually, ALS results in death.

The hip joint is one of the largest weight-bearing joints in the body. This ball-and-socket joint allows the leg to move and rotate while keeping the body stable and balanced. Let's take a closer look at the main parts of the hip joint's anatomy.

The knee is the body's largest joint. It's the place where three bones meet: the tibia, the femur and the patella. The knee is a "hinge" joint. It allows the leg to bend in one direction only. Let's take a closer look at the main parts of the knee's anatomy.

The shoulder is a complex structure made of three separate joints. They work together to give the shoulder a tremendous range of motion. Let's take a closer look at the main parts of the shoulder's anatomy.

These are warm or painful sensations caused by an injury to the brachial plexus. This is a network of nerves that passes through your shoulder. They travel down your arm and to your hand.

This is an irritation or swelling of the trochanteric bursa. This small, fluid-filled sac is found on the outer side of the femur. It acts as a cushion for the iliotibial band, a thick tendon in your leg.

Pain, numbness and tingling in your hand may be from carpal tunnel syndrome. It happens when the area around the main nerve to your hand is too tight. The nerve is called the median nerve. And the small space in your wrist where it passes is called the carpal tunnel.

This group of disorders involves the brain. It affects movement, balance and posture. It can cause other serious issues.

This movement disorder causes your neck muscles to contract. Your head may turn or tilt. This can happen in brief spasms, or it can be a constant contraction. You can't control it, and it may be painful. Cervical dystonia can disrupt your daily life.

This is a type of chronic, long-lasting, pain. In most cases, it develops in an arm or a leg that you have previously injured. With CRPS, you may have unexplained pain that won't go away. It may be severe, and it may spread.

This condition, also called "ulnar nerve entrapment," happens to the ulnar nerve in your elbow. This nerve travels along the inner side of your elbow and down to your hand. It's the nerve that makes the jolt you feel when you bump your "funny bone." With this condition, your ulnar nerve is compressed, stretched or irritated.

This movement disorder involves muscle contractions you can't control. You might experience cramping or twisting. You might make slow, repetitive movements. It can affect one or more parts of your body. Dystonia can be painful. And it may make daily tasks hard to do.

This is a disorder of the nervous system that we call "GBS." With it, your immune system mistakenly attacks your peripheral nerves. These are the nerves that link your brain and spinal cord to the rest of your body. They control things like sensation and movement. When they are damaged, you can have severe problems.

This condition, commonly called tennis elbow, is an inflammation of the tendons that connect the muscles of the forearm to the elbow. The pain is primarily felt at the lateral epicondyle, the bony bump on the outer side of the elbow.

This is a bacterial infection you get from a tick bite. It can spread through your body, causing flu-like symptoms. In some people, it can cause problems that last a long time.

This condition, commonly called golfer's elbow, is an inflammation of the tendons that connect the muscles of the forearm to the elbow. The pain is primarily felt at the medial epicondyle, the bony bump on the inner side of the elbow.

This type of arthritis, also called "degenerative joint disease," is a breakdown of the cartilage in your hip joint. As this protective cartilage wears away, bone rubs against bone. Bony growths called "bone spurs" may form in the joint. Pain from osteoarthritis can keep you from being as active as you like.

Knee pain may keep you from being as active as you like. And it may come from a gradual breakdown of your knee's cartilage. That's a protective tissue on the ends of your bones. In a healthy knee, the bones glide smoothly against each other. But in a knee with osteoarthritis, cartilage begins to wear away. Bone rubs against bone. Bony bumps we call "bone spurs" may form.

If you have an infection in a bone, you have osteomyelitis. It's a serious condition that can cause part of your bone to die. And, the infection can spread to other parts of your body.

Plantar fasciitis is an irritation of the plantar fascia. This thick band of connective tissue travels across the bottom of the foot between the toes and the heel. It supports the foot's natural arch. It stretches and becomes taut whenever the foot bears weight.

This condition involves the radial nerve in your elbow. The radial nerve passes down your arm to your hand. Its branches travel into your thumb, forefinger and middle finger. With this condition, your radial nerve is compressed, stretched or irritated.

This is a painful pinching of soft tissues in your shoulder. It happens when these tissues rub and press against a part of your shoulder blade called the "acromion." This can irritate your rotator cuff tendons, and also a soft sac called the "subacromial bursa."

This is a pain or weakness from an irritated nerve in your shoulder. It's called the "suprascapular" nerve. It travels from the neck down through your shoulder.

This is a label given to a group of disorders. In these disorders, nerves or blood vessels are compressed in the space between your collarbone and the underlying rib. This space is called the "thoracic outlet."