Radius: anatomy, function and treatment


The radius is the thickest and shortest of the two long bones in the forearm. It is located on the lateral side of the forearm parallel to the ulna (in anatomical position with the arms hanging at the sides of the body, palms facing forward) between the thumb and the elbow. The radius and ulna rotate around each other, allowing the wrist to rotate. Together, along with the humerus, they form the elbow joint.

The radius is often considered the larger of the two long bones in the forearm because it is thicker than the ulna at the wrist but thinner at the elbow. The ulna is about an inch longer than the radius in most people, but it varies considerably in length.

Of the two bones in the forearm, the probability of fracture of the radius is greater than that of the ulna. In children, more than 50% of all forearm fractures affect only the radius, 6% only the ulna, and 44% both. Radial fractures are also very common in adults. Men and women have similar cases of radius fractures until their mid-40s, when they become much more common in women than in men.


The radius is a long bone, one of the four types of bones in the body. The long bone is a dense, strong bone that is longer than it is wide. The trunk is known as the diaphysis and the end of the long bone is the pineal gland. The shaft is hollow, with a space inside called the medullary canal. The bone marrow is located in the medullary canal.


The radius is 8 to 10.5 inches long in adults. It averages 9.5 inches for men and 8.8 inches for women . The distal epiphysis of the radius (the end furthest from the wrist) is, on average, about an inch wide. The proximal pineal gland (ends at the elbow) is about half as long.

As described above, the radius is a typical long bone with dense hard bone along the axis (axis). Cancellous bone is present at the ends of the radius, which hardens with age.

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The radius is located in the forearm, the part of the arm between the elbow and the wrist. In the anatomical position with the arms straight and the palms extended forward at the level of the hips, the radius is parallel and lateral (outside) of the ulna. In a resting position, for example, when you keep your hands on the keyboard, the distal (far) ends of the radius and ulna intersect the radius at the vertex of the ulna.

The proximal end of the radius forms the lateral (outer) edge of the elbow at the distal end of the humerus. The distal end of the radius is attached to the wrist just in front of the thumb.

Rotation of the radius and ulna allows the wrist to be rotated at the distal radial joint. The radius provides stability to the hinge joint at the elbow joint and allows movement at the radius-shoulder joint, but the ulna and humerus do most of the work. There is some movement between the proximal end of the radius and the elbow joint, called the proximal radius joint.

The radius and ulna are connected by a sheet of thick fibrous tissue called the interosseous ligament or interosseous membrane. A smaller ligament connects the proximal ends of the radius and the ulna. It is known as the oblique cord or oblique ligament, and its fibers run in the opposite direction to the interosseous ligament.

Anatomical variations

In some cases, the radius may be short, underdeveloped, or absent. One type of radial anatomy is proximal radioulnar synostosis, in which the bones of the radius and ulna fuse, usually in the proximal third (the third, closest to the elbow). This condition can be congenital. But this can happen in rare cases after a bone injury, such as a dislocation.


The radius allows movement of the arms and, in particular, provides a full range of motion for the hand and wrist. The radius and ulna work together to provide a lever for elevation and rotation when manipulating objects. When crawling, the radius can also help provide mobility.

The radius provides support for the body weight when using the arms when crawling and lifting body weight, such as during push-ups. The radius has seven muscle attachment points for support of the instep, biceps brachii, superficial flexor of the fingers, circular pronator, long flexor of the thumb, humerus and pronator quadratus.

Related conditions

The most common disorder of the radius is a fracture. The radius, although shorter and slightly thicker than the ulnar, is broken more often. It would appear that more force would be exerted on the longer ulna during falls or other mechanisms of injury. However, it is the radius of the radius that is one of the most common fractures among all age groups. The weight distribution when landing from the ground, when the patient breaks the fall with the hands down, exerts the greatest pressure on the radius. A fracture of only the radius, only the ulna, or both bones of the forearm is possible.

Distal radius fractures are the most common type of radius fracture. Elderly and pediatric patients are at greater risk than younger adult patients when they fall on an outstretched arm (sometimes called a FOOSH injury ) . Elderly patients are at risk for radial head fractures, which refers to the proximal end of the radius that is part of the elbow.

Pediatric patients are more likely to have incomplete fractures, often called green rod fractures , due to the flexibility of the immature bone. Preadolescent patients are also at risk of damaging the epiphyseal plate (growth plate). Damage to the growth plate can lead to permanent deformation .

Regardless of the type or severity of the radius fracture, you should expect symptoms that are common to all long bone fractures. Pain is the most common symptom of any fracture and the only symptom that can be considered universal. Pain after falling onto an outstretched arm can lead to pain in the wrist, forearm, or elbow. All of this may indicate a fracture of the radius.

Any other signs or symptoms of a fracture may or may not be present. Other signs and symptoms of a fracture include deformity, tenderness, crepitus (a grinding or grinding sound from the ends of broken bones), swelling, bruising, and loss of function or sensation .

Radiation fractures are not life threatening and do not require emergency care, not even a visit to the emergency room. Often times, a visit to the doctor can start the process of diagnosing and treating a radiation fracture if the doctor can order an X-ray.


Treatment and rehabilitation of the radius after a fracture depends on the severity and location of the injury. Treatment begins with immobilization of the fracture site. The ends of the bone must return to the correct anatomical position (called a contraction) to promote proper healing. If the bone is not inserted in the correct position, new bone growth can lead to permanent deformity .

The type of reduction and immobilization required depends on the type and location of the fracture. Severe fractures may require surgical immobilization, while minor fractures may be immobilized through manipulation and application of a cast or splint. In many cases, slings are also needed to improve immobilization as the patient moves through life during the several weeks required for healing. fracture.

After immobilization, long-term rehabilitation includes physical therapy . The physical therapist can teach the patient to perform stretching and strengthening exercises that apply adequate pressure to the correct areas after the fracture. Physical therapy will work to improve elbow and wrist strength and range of motion . Physical therapy for the shoulder may also be required due to immobilization of the injured arm. The inability to use the forearm means that the patient is also likely to have little shoulder movement.

Surgical treatment or reduction of severe fractures may require more than one operation to fully repair the injury. Each surgery requires a healing period and the patient may require physical therapy to return to preoperative functions. For some injuries, several months may elapse between surgeries, which will require rehabilitation after each procedure.

Rehabilitation of a radius fracture can take two to three months to fully recover to the pre-injury condition. It is important to follow physical therapy and be aware of all exercises and treatments. Long breaks between classes or no exercise outside of the physical therapy room can prevent healing or even lead to a new injury.

Frequently asked questions

  • The proximal refers to the part of the body that is closest to the point of attachment and the distal is furthest from the point of attachment. They act as opposites to each other.

    For example, the shoulder is close to the body and the hand is distal.

    Here's another way to remember the difference:

    • Proximal – Proximity (near)
    • Distal – Distance (far)

  • The radius is long-boned. There are four types of bones in the human body.

    • Long bone: longer than wide
    • Short bone: Approximately the same width as the length.
    • Flat bone: provides structure, like the cranial bones of the skull.
    • Irregular bone: it is not long, short or flat, these bones have very specific functions that can only appear once or twice in the body. An example is the cheekbone (cheekbones).

  • The shaft is the term used to define the axis of a long bone, such as the radius. The space within the diaphysis is called the medullary canal, which is filled with bone marrow. The end of a long bone is called the pineal gland.

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