The inability to fully straighten the arm after a fall, known as loss of elbow extension, signals a serious structural problem within the joint. This symptom is usually caused by a mechanical or functional block preventing the bones from achieving normal alignment, rather than just pain or muscle guarding. Because the elbow is a complex hinge joint stabilized by bone, ligaments, and tendons, this specific symptom requires immediate professional evaluation to prevent long-term disability.
Structural Damage: Fractures and Dislocations
The most direct cause of a blocked elbow joint is a physical disruption of the bony architecture. A fall onto an outstretched hand transmits force up the forearm, resulting in fractures that physically prevent full extension. A frequent injury is a radial head fracture, involving the rounded end of the radius bone near the elbow. Displaced fragments can jam the joint, making any attempt to straighten the arm painful and impossible beyond a certain point.
Another severe bony injury is an olecranon fracture, a break in the prominent tip of the ulna bone at the back of the elbow. This injury is disruptive because the olecranon is the attachment point for the triceps muscle, the primary muscle responsible for straightening the arm. A fracture means the triceps cannot effectively pull the bone to extend the elbow, resulting in a functional loss of extension against gravity. In children, a supracondylar fracture of the humerus, the bone just above the joint, is a common injury from a fall that makes arm extension impossible.
A dislocation, where the elbow bones are forced out of normal alignment, represents a serious structural failure. The humerus separates from the radius and ulna, causing the joint to become visibly deformed and locked in a bent position. Even a simple dislocation causes massive soft tissue disruption and a profound inability to move the limb. In complex cases, the dislocation is accompanied by fractures, such as the radial head, which severely compromises joint stability and movement.
Soft Tissue Injuries Limiting Range of Motion
Severe damage to the soft tissues surrounding the elbow can prevent the arm from straightening, even without a broken bone. A complete tear, or rupture, of the triceps tendon detaches the muscle from the olecranon, eliminating the primary power source for extension. The injured person experiences profound weakness and cannot actively push the arm straight against gravity, even if the bones are intact.
Severe sprains (Grade III injuries) involve a complete tear of stabilizing ligaments, such as the ulnar or radial collateral ligaments. Their rupture can lead to joint instability and posterolateral rotatory instability. This instability causes joint surfaces to temporarily shift out of position during attempted movement, preventing full extension. The body often responds to this damage with a protective muscle spasm and intense pain, guarding the joint from further movement.
Internal Swelling Causing Mechanical Blockage
A significant reason for the inability to fully extend the elbow is the rapid accumulation of fluid inside the joint capsule. Trauma causing a fracture or severe ligament damage can lead to hemarthrosis, which is bleeding into the joint space. Since the elbow joint is a tightly confined space, the presence of blood or inflammatory fluid quickly increases internal pressure. This accumulation physically occupies space within the capsule, creating a mechanical block that limits the bones’ ability to move through their full range of motion. The pressurized capsule prevents the joint from fully opening, which is why even simple, non-displaced fractures can result in a dramatic loss of extension immediately following the injury.
Urgent Medical Steps and Professional Diagnosis
The acute inability to straighten the arm after a fall requires immediate professional attention. Attempting to force the arm straight can cause further damage to nerves, blood vessels, or bone fragments. The most important immediate step is to immobilize the arm in the position of comfort, typically with a sling, and avoid all attempts at movement.
Diagnostic Imaging
Once medical attention is sought, a physician will perform a physical examination and order diagnostic imaging. An X-ray is the standard initial step to check for fractures and dislocations. If the X-ray is negative but symptoms persist, a more detailed assessment may include a Computed Tomography (CT) scan for complex bone fragments. A Magnetic Resonance Imaging (MRI) scan may also be used to visualize soft tissue damage like ligament or tendon tears.
Initial Home Care
For initial home care, modified RICE principles should be followed: rest, ice, compression, and elevation. Avoid applying heat, as this can increase swelling and internal pressure in the acute phase.