The inability to fully straighten the arm after a fall is a serious sign of significant trauma to the elbow joint. This symptom, often accompanied by intense pain, suggests a structural disruption, mechanical blockage, or severe internal swelling requiring immediate medical attention. The elbow is a complex hinge joint involving the humerus, ulna, and radius. Any injury preventing full extension means the intricate alignment or surrounding soft tissues have been compromised. Attempting to force the joint straight can cause further damage.
Structural Injuries Preventing Arm Extension
The most direct reason the arm cannot straighten is a physical obstruction within the joint, typically caused by a fracture or dislocation. These injuries create a mechanical blockage where a misaligned bone or fragment stops the hinge motion of the elbow.
A common structural cause is a radial head fracture, often resulting from falling onto an outstretched hand. The impact drives the radius against the humerus, breaking the radial head, which is essential for bending and forearm rotation. A displaced radial head fracture physically impedes smooth joint movement, preventing full extension or causing extreme pain.
An olecranon fracture directly interrupts the elbow’s extensor mechanism. The olecranon is the pointy bone at the back of the elbow where the triceps muscle attaches. When fractured, the triceps pulls the broken bone fragment away from the joint. If the fracture is displaced, the continuity needed for the triceps to pull the arm straight is lost, resulting in an inability to extend the elbow against gravity.
A full elbow dislocation, where the ulna and radius separate from the humerus, also prevents arm straightening. The joint components are misaligned, making extension impossible until the joint is reduced (put back into place). Severe tears to ligaments, such as the ulnar collateral ligament (UCL) or lateral collateral ligament (LCL), can destabilize the joint, compromising or physically preventing full extension.
How Severe Swelling Limits Movement
Beyond mechanical obstruction, severe swelling—the body’s immediate response to trauma—can also prevent full arm extension. This restriction is caused by pressure and a protective neurological mechanism, even if no bone fragment is blocking the joint.
Significant trauma causes joint effusion, which is the accumulation of fluid within the elbow capsule. If blood is involved, this is called hemarthrosis. The increased volume and pressure inside the joint physically limit the space available for the bones to move, preventing full extension. Movement is painful when attempting to compress the fluid-filled capsule.
Pain inhibition is a separate, protective neurological reflex that restricts movement. Pain signals cause surrounding muscles, particularly the biceps, to involuntarily spasm or guard the area. This muscular tension prevents the arm from relaxing into a straightened position, creating a functional restriction. This protective response contributes significantly to the immediate loss of range of motion.
Immediate Steps After Injury and Medical Triage
The inability to straighten the arm after a fall must always be treated as a medical emergency requiring professional evaluation. Until you reach a medical facility, focus on stabilizing the injury and managing swelling and pain.
Do not attempt to forcefully straighten the arm or “pop” the joint back into place, as this risks causing damage to nerves, blood vessels, or soft tissues. Initiate the immediate care protocol: RICE (Rest, Ice, Compression, Elevation).
- Rest the limb.
- Apply ice wrapped in a cloth for short periods.
- Gently compress the area, avoiding excessive pressure.
- Elevate the elbow above the heart to reduce swelling and pressure.
The arm should be temporarily immobilized in a comfortable position, often using a sling, to prevent accidental movement that could displace a fracture or cause further strain.
Diagnosis
Upon arrival, triage starts with a physical examination to assess neurovascular status, checking for sensation, pulse, and movement in the hand and fingers. Diagnostic imaging determines the exact cause of the blockage. Standard X-rays identify fractures, dislocations, and alignment issues. For complex cases, a CT scan may visualize comminuted fractures, and an MRI may evaluate soft tissue damage, such as ligament tears.
The Path to Regaining Full Range of Motion
The ultimate goal after treating the injury is to restore the elbow’s full range of motion, beginning after the initial repair and healing phase. Treatment involves a period of immobilization, followed by a dedicated rehabilitation program.
For fractures, treatment may involve casting, splinting, or surgery to fix bone fragments with plates and screws. Dislocations require immediate closed reduction to realign the joint, sometimes followed by surgery if ligaments are torn and the joint remains unstable. Regardless of the initial treatment, the elbow is prone to stiffness, and regaining terminal extension is often the most difficult part of recovery.
Physical therapy is the cornerstone of rehabilitation, focusing on gradually and safely restoring movement to the stiff joint. Therapists guide the patient through range-of-motion exercises, differentiating between active motion (using your own muscles) and passive motion (using a therapist or device to gently push the joint). Specific techniques, such as joint mobilization, encourage the joint capsule and surrounding tissues to stretch and allow for full extension.
While significant functional recovery is expected, a minor loss of terminal extension (sometimes 10 to 15 degrees) is a common outcome, especially after complex injuries. A consistent approach to rehabilitation minimizes the risk of long-term stiffness and helps ensure the best possible functional result.