Radius

The forearm contains two long bones. In the anatomical position (with the palms facing forward), the radius is on the thumb side and the ulna is on the little-finger side. The radius is narrow at the top and wide at the bottom, while the ulna is the reverse: wide at the top and narrow at the bottom. The two bones form a pair with their wider ends at opposite ends.

At its upper end, the radius meets the elbow. Its uppermost part is a round, disc-shaped head (the radial head), with a narrow neck (the radial neck) just below it. The tendon of the biceps brachii, which bends the arm and rotates the forearm outward, attaches to a prominence below the neck called the radial tuberosity. On the outer side of the lower end is a pointed styloid process, where the brachioradialis muscle attaches.

The radius forms joints at four locations.

The middle two joints make pronation and supination possible. With the palm facing up, the two bones lie parallel. When the palm turns down, the radius crosses over the ulna to form an X shape.

• During twisting movements. The radius rotates around the ulna whenever you turn a doorknob, open a bottle cap, or turn a screwdriver.
• On the thumb side of the wrist. The spot on the palm side of the wrist near the thumb where you can feel a pulse is where the radial artery passes over the radius.
• When bearing weight. During movements that load the wrist, such as push-ups, downward-facing dog in yoga, and bench presses, the end of the radius bears a substantial amount of the load.
• When you fall onto your hand. Landing on your hand during a fall concentrates the impact at the wrist end of the radius, which is known as a common site of fractures near the wrist.
• At a young child's elbow. A sudden pull on a child's hand can cause the radial head to slip slightly out of its ligament, so it is best not to yank a child's hand when walking together.

• The radius and the radial nerve. Although their names are similar, the radial nerve is a nerve. It winds around the back of the upper arm and travels downward, controlling the muscles that straighten the elbow and wrist. It passes close to the radius but does not pass through the bone.
• The wrist bones and the end of the radius. Of the eight carpal bones that make up the wrist, the scaphoid and lunate bone meet the end of the radius. These are separate bones that articulate with it.
• The little-finger side of the wrist. The triangular fibrocartilage complex lies between the end of the ulna and the wrist bones. This area is discussed separately under Triangular fibrocartilage complex injury.

• Loosen up the wrist and forearm. Extend your arm forward and slowly practice alternating between turning your palm up and down. Gentle stretches that bend and extend the wrist can also help.
• Warm up before putting weight on your wrists. Before exercises that involve placing your hands on the floor, try circling your wrists and gently pressing through your palms to help your body adapt.
• Strengthen the forearm muscles. Wrist flexion and extension exercises with a light dumbbell let the muscles share the load on the wrist. A good balance between the wrist flexors and wrist extensors can make the wrist feel more comfortable.
• Consider wrist guards or gloves in slippery conditions. On snowy paths or during roller sports, equipment that protects the wrists during a fall can help.

• The wrist is swollen and looks misshapen after a fall
• A catching sensation or pain when rotating the wrist does not go away
• Pressing on the outside of the elbow hurts, and rotating the forearm is uncomfortable
• A child is reluctant to move their arm and appears to be in pain

In these situations, an X-ray assessment at an orthopedic clinic is common.