Abduction: Joint movement away from the midline of the body.

Active range of motion: The degree of movement a patient can voluntarily achieve in a joint without assistance.

Adduction: Joint movement toward the middle line of the body.

Arthroplasty: Joint replacement surgery.

Arthroscopic surgery: A surgical procedure involving a small incision and the insertion of an arthroscope, a pencil-thin instrument that allows for visualization of the joint interior. Small surgical instruments are inserted via additional incisions to remove or repair ligaments and other joint structures.

Articular cartilage: Smooth, white tissue that covers the ends of bones where they come together at joints, allowing them to glide over each other with very little friction. Articular cartilage can be damaged by injury or normal wear and tear.

Clubfoot: A congenital condition that causes the foot and lower leg to turn inward and downward.

Congenital condition: A condition present at birth.

Contracture: A fixed or permanent tightening of muscles, tendons, ligaments, or the skin that prevents normal movement of the body part.

Crepitus: A crackling, popping noise heard on joint movement. It is considered normal when it is not associated with pain.

Dislocation: A joint injury that forces the ends of bones out of position; often caused by a fall or a blow to the joint.

Extension: Joint movement causing the straightening of limbs (increase in angle) at a joint.

Flexion: Joint movement causing the bending of the limbs (reduction of angle) at a joint.

Foot drop: The inability to raise the front part of the foot due to weakness or paralysis of the muscles that lift the foot.

Fracture: A broken bone.

Gout: A type of arthritis that causes swollen, red, hot, and stiff joints due to the buildup of uric acid, commonly starting in the big toe.

Joints: The location where bones come together.

Kyphosis: A curving of the spine that causes a bowing or rounding of the back, leading to a hunchback or slouching posture.

Ligaments: Strong bands of fibrous connective tissue that connect bones and strengthen and support joints by anchoring bones together and preventing their separation.

Lordosis: An inward curve of the lumbar spine just above the buttocks. A small degree of lordosis is normal, but too much curving is called swayback.

Muscle atrophy: The thinning or loss of muscle tissue that can be caused by disuse, aging, or neurological damage.

Open fracture: A type of fracture when the broken bone punctures the skin.

Osteoarthritis: The most common type of arthritis associated with aging and wear and tear of the articular cartilage that covers the surfaces of bones at the synovial joint.

Osteoporosis: A disease that thins and weakens bones, especially in the hip, spine, and wrist, causing them to become fragile and break easily.

Passive range of motion: The degree of range of motion a patient demonstrates in a joint when the examiner is providing the movement.

Rheumatoid arthritis: A type of arthritis that causes pain, swelling, stiffness, and loss of function in joints due to inflammation caused by an autoimmune disease.

RICE: A mnemonic for treatment of sprains and strains that stands for: Resting the injured area, Icing the area, Compressing the area with an ACE bandage or other device, and Elevating the affected limb.

Rotation: Circular movement of a joint around a fixed point.

Scoliosis: A sideways curve of the spine that commonly develops in late childhood and the early teens.

Skeletal muscle: Voluntary muscle that produces movement, assists in maintaining posture, protects internal organs, and generates body heat.

Sprain: A stretched or torn ligament caused by an injury.

Strain:  A stretched or torn muscle or tendon.

Synovial fluid: A thick fluid that provides lubrication in joints to reduce friction between the bones.

Synovial joints: A fluid-filled joint cavity where the articulating surfaces of the bones contact and move smoothly against each other. The elbow and  knee are examples of synovial joints.

Tendons: Strong bands of dense, regular connective tissue that connect muscles to bones.