The sudden inability to fully straighten your arm at the elbow signals a problem within the joint’s structure. This physical restriction, often accompanied by pain or a “locked” sensation, means the normal hinge mechanism of the elbow is blocked. The elbow is a hinge joint, and any mechanical or inflammatory disruption can severely limit its range of motion, particularly terminal extension. Causes range from immediate, high-energy trauma to gradual, chronic wear-and-tear conditions. Any persistent loss of motion requires professional medical evaluation.
Acute Injuries Causing Restriction
Acute injuries involve a sudden, traumatic event resulting in the immediate loss of full elbow extension. An elbow dislocation occurs when the forearm bones are forcibly shifted out of alignment relative to the humerus, creating a physical block. This high-energy event often causes significant tearing of supportive ligaments and the joint capsule, leading to severe pain and visible deformity. Even after realignment, patients commonly experience a loss of terminal extension, sometimes 10 to 15 degrees, due to soft tissue damage and subsequent scarring.
Fractures around the elbow, such as the olecranon, radial head, or supracondylar region, can also mechanically impede movement. Broken bone fragments or severe internal swelling can take up space within the joint capsule, preventing the final degrees of extension. A displaced olecranon fracture, for instance, directly compromises the mechanism responsible for straightening the arm.
Severe soft tissue injuries, like a complete distal biceps tendon tear, cause acute restriction. Although the biceps primarily flexes the elbow, a complete tear causes intense pain and swelling. The resulting loss of structural integrity and protective muscle guarding limits full extension.
Inflammatory and Overuse Conditions
Conditions developing gradually, often due to repetitive stress, cause restriction primarily through inflammation, swelling, and pain. Tendonitis, such as Golfer’s Elbow or Tennis Elbow, involves irritation of the tendons connecting the forearm muscles to the elbow. The resulting inflammation and pain cause surrounding muscles to involuntarily tighten in a protective spasm, making full straightening painful or impossible.
Olecranon bursitis is characterized by fluid accumulation in the bursa sac over the bony point of the elbow. When the bursa becomes irritated, it swells significantly. This fluid buildup creates a soft physical mass that mechanically restricts the final motion of extension.
Severe muscle strains or contusions, particularly to the triceps, can also limit movement. A significant tear or bruise leads to inflammation and pain. The body guards the injured area by holding the joint flexed, and the resulting swelling prevents the arm from being forced straight without intense discomfort.
Chronic Joint and Structural Issues
Long-term, structural changes inside the joint can physically block the elbow’s ability to straighten.
Osteoarthritis and Bone Spurs
Osteoarthritis, involving the degeneration of joint cartilage, is a common cause of chronic extension loss. As cartilage wears away, the body forms bony growths called osteophytes or bone spurs, often on the back of the joint. These osteophytes abut one another when the arm attempts to straighten, creating a firm, bony block that permanently restricts terminal extension.
Loose Bodies
Loose bodies, often called “joint mice,” are fragments of bone or cartilage that float freely within the joint space. These fragments frequently result from osteoarthritis or prior injury. Loose bodies can intermittently become lodged in the elbow’s hinge mechanism, causing sudden, sharp pain and a locking sensation that physically prevents full extension.
Post-Traumatic Contractures
Post-traumatic contractures are a permanent tightening of soft tissues following a fracture or dislocation. Immobilization causes the joint capsule and ligaments to thicken and shorten, restricting motion even after healing. This scarring and tightness, sometimes involving heterotopic ossification, acts as a mechanical restraint, making it impossible to regain the full, straight position.
Seeking Diagnosis and Treatment
The inability to straighten your arm requires prompt medical attention, particularly if the symptom appeared suddenly with severe pain, a visible deformity, or accompanying numbness and weakness. These signs may indicate an acute fracture, dislocation, or nerve/vascular compromise, necessitating immediate assessment in an urgent care or emergency setting. For less acute cases, a physician will perform a thorough physical examination, testing both active and passive range of motion and assessing joint stability.
Diagnostic imaging confirms the underlying cause of restricted extension. X-rays visualize bony structures, identifying fractures, bone spurs, and loose bodies. MRI or ultrasound provides detailed images of soft tissues, assessing tendon tears, ligament damage, bursitis, or inflammation.
Treatment depends on the diagnosis, but initial non-surgical approaches include rest, anti-inflammatory medications, and physical therapy to restore motion. For acute soft tissue issues, the RICE protocol helps manage pain and swelling:
- Rest
- Ice
- Compression
- Elevation
Chronic structural issues, such as bone blocks from osteophytes or problematic loose bodies, may require surgical intervention. Minimally invasive arthroscopy is often used to remove the physical impediment and restore the joint’s full range of motion.