Where Is the Radius Located in Your Arm?

Our forearm is a highly functional part of our body. There are two bones inside it, radius and ulna. Your radius rotates over your ulna when you extend your arm straight out with your palms facing down. But where is the radius located? Let’s find out:

Radius Bone Anatomy

The radius is one of the two main bones in the forearm. It runs parallel to the ulna and is located on the thumb side. It’s a long, prism-shaped bone that is crucial for arm and wrist movement.

1. Proximal End
   The proximal end of the radius has several important parts:
   • Head: A disc-shaped structure that connects with the humerus at the elbow joint, allowing smooth movement.
   • Neck: A narrow section that links the head to the radial tuberosity.
   • Radial Tuberosity: A bony bump just below the neck where the biceps muscle attaches, which helps bend the elbow.
2. Shaft
   The shaft is the long, central part of the radius. It is slightly curved and triangular in cross-section, with three borders (front, back, and interosseous) and three surfaces (front, back, and side). The shaft gets wider as it goes towards the distal end.
3. Distal End
   The distal end of the radius is wider and has several key features:
   • Ulnar Notch: A concave surface that connects with the head of the ulna to form the distal radioulnar joint.
   • Styloid Process: A prominent bony projection on the side, where wrist ligaments attach.
   • Carpal Articular Surface: This surface has two facets that connect with the scaphoid and lunate bones of the wrist, allowing wrist movement.

Where Is the Radius Located for Functionality?

The radius bone is crucial for the stability of the forearm and wrist. The following are its main functions:

• Facilitating Arm Movement
  The radius allows the forearm to rotate. It enables supination (palm facing up) and pronation (palm facing down). The radial head rotates within the annular ligament and the radial notch of the ulna, making these movements possible.
• Articulating with Other Bones
  The radius forms joints with the humerus at the elbow and the carpal bones at the wrist. At the elbow, it connects with the capitulum of the humerus, allowing the arm to bend and straighten. At the wrist, it connects with the scaphoid and lunate bones, enabling wrist movements like flexion, extension, and deviation.
• Supporting Muscles and Tendons
  Many muscles, tendons, and ligaments attach to the radius. The biceps brachii muscle attaches to the radial tuberosity, helping to bend the elbow. Other muscles, like the pronator teres and supinator, also attach to the radius, aiding various forearm and hand movements.
• Weight Bearing and Stability
  The radius supports the forearm’s weight and provides stability during activities like lifting or pushing. Its structure helps withstand forces during these movements, adding to the forearm’s strength.

Common Radius Bone Fractures

The forearm is a common site for bone fractures. Following are some common types of fractures involving the radius:

• Colles’ Fracture
  It is the most common type of radial fracture. It occurs from a fall onto an outstretched hand. The distal radius is fractured, and the wrist and hand are displaced backward. It produces a ‘dinner fork deformity.
• Fractures of the Radial Head
  It can happen when you fall on the outstretched hand. The radial head is pushed into the capitulum of the humerus, causing a fracture.
• Smith’s Fracture
  This fracture occurs when a person falls onto the back of the hand. Therefore, it is the opposite of a Colles’ fracture. In this, the distal fragment of the radius is displaced forward.

Wrapping Up

Radius bone fractures are common. Therefore, a constant or intense pain in your forearm can make you think, “Where is the radius located?” so you can figure out the fracture type on your own. However, an orthopedic doctor is the best option to look forward to. 

Visit Dr. Luo at Randy Y. Luo, MD, MBA. Our board-certified orthopedic surgeon specializes in hand and upper extremities to treat your hand and arm injuries effectively. Dial one of the following numbers for an appointment:

Houston: (713) 794-3307

Houston: (713) 799-2300

SugarLand: (713) 794-3457