The instinctive human reaction to an unexpected loss of balance is to rapidly extend the upper limbs to cushion the impact with the ground. This common scenario is a major cause of injuries to the hand, wrist, and arm, particularly in orthopedic settings. Understanding this involuntary action is important because it accounts for a large percentage of all upper extremity fractures and dislocations. This trauma mechanism is grouped under a single acronym in medical practice.
The Mechanism of Injury
The term used to describe this specific event is FOOSH, which stands for “Fall Onto an Outstretched Hand.” This protective reflex is designed to keep the head and torso from striking the ground. However, it redirects the entire force of the fall through a single limb. The hand hits the surface first, often with the wrist hyperextended, immediately transferring the kinetic energy of the falling body up the arm.
The impact force travels from the small bones of the hand, through the wrist joint, and continues up the forearm bones—the radius and ulna—to the elbow and shoulder. The degree of injury depends on the angle of the wrist at impact, the speed of the fall, and the individual’s bone density. When the hand is extended, the radius, the larger of the two forearm bones, bears approximately 80% of the axial load, making it vulnerable.
Common Anatomical Consequences
The transfer of force through the FOOSH mechanism results in a predictable pattern of injuries, with the wrist being the most frequently affected joint. The most common injury is a distal radius fracture, which is a break in the larger forearm bone near the wrist. A specific type, known as a Colles’ fracture, occurs when the broken bone fragment is displaced backward (dorsally). This fracture is common, especially among older adults with lower bone density.
Another frequent wrist injury is a scaphoid fracture, involving one of the eight small carpal bones located on the thumb side of the wrist. Scaphoid fractures are concerning because the bone has a limited blood supply, increasing the risk of delayed healing or non-union. This can lead to complications like avascular necrosis, where bone tissue dies due to lack of blood flow.
The force can also travel further up the arm, causing injuries at the elbow and shoulder. At the elbow, a radial head fracture is a common outcome, involving the part of the radius bone that forms the elbow joint. Pain and limited rotation of the forearm can indicate this injury. In the shoulder, the impact may lead to a clavicle (collarbone) fracture or a dislocation of the shoulder joint, where the arm bone pops out of its socket.
Immediate Care and Medical Evaluation
Following a suspected FOOSH injury, immediate care should focus on stabilization and reducing swelling. The RICE protocol—Rest, Ice, Compression, and Elevation—can be initiated as a first response. The injured limb should be rested and kept immobile to prevent worsening the damage. Applying ice wrapped in a cloth for 15 to 20 minutes several times a day helps reduce pain and swelling, while elevating the arm above the heart minimizes fluid buildup.
It is important to seek a professional medical evaluation quickly, even if the injury appears minor. Many serious fractures, particularly scaphoid fractures, may not cause a visible deformity and can be mistaken for a simple sprain. A medical assessment begins with a physical examination to check for tenderness, swelling, and loss of motion.
Imaging tests are used to confirm the diagnosis and determine the extent of the damage. Standard X-rays are the primary tool for identifying fractures and dislocations. However, some subtle breaks, like certain scaphoid or radial head fractures, may require specialized views or follow-up imaging. Early and accurate diagnosis is necessary to ensure proper treatment, which may range from casting and splinting to surgical intervention for complex injuries.