Extensor tendonitis is characterized by inflammation and irritation of the extensor tendons, the tissues responsible for straightening a joint. These tendons are located on the back of the hand and wrist, allowing you to lift your fingers and hand, and across the top of the foot, enabling you to lift your toes and ankle upward. Pain and swelling occur when damage interrupts the tendon’s smooth, gliding motion. Understanding the causes, which range from mechanical stress to biological processes, is essential for effective management and prevention.
The Role of Repetitive Strain and Overuse
The most frequent cause of extensor tendonitis is the mechanical breakdown of tendon tissue from repeated stress over time. Constant, low-level strain without adequate recovery leads to an accumulation of microscopic tears, initiating an inflammatory response. This occurs when the volume of activity exceeds the tendon’s ability to repair itself.
In the hands and wrists, this injury affects individuals performing high-volume, repetitive tasks. Examples include extensive computer keyboard and mouse use, gripping tools, playing musical instruments, or engaging in sports like rowing or racquet sports. These repetitive extension and flexion cycles cause friction and strain on the tendons as they pass through their sheaths.
Extensor tendonitis in the foot is common among runners and those who stand for prolonged periods. The tendons on the top of the foot constantly work to lift the toes during the swing phase of walking or running. Activities like high-impact jumping or long-distance running place continuous stress on these tendons, leading to gradual inflammation and pain.
How Poor Technique and Ergonomics Contribute
While the volume of activity drives overuse, poor technique and setup significantly accelerate tendon damage. Poor ergonomics involves positioning the body or equipment unfavorably, forcing tendons to work at awkward angles or under unnecessary load. This mechanical disadvantage places excessive strain on the tendons even during normal activity.
For hand and wrist extensor tendons, a common issue is maintaining the wrist in an extended position while typing or using a mouse. This posture compresses the tendons and requires extensor muscles to be constantly engaged, increasing friction and reducing blood flow. Gripping objects too forcefully, such as a pen or tennis racket, also creates high tension in the extensor muscles that stabilize the wrist.
In the foot, poor technique often relates to footwear and gait mechanics. Shoes that are too tight, especially in the toe box, or shoelaces tied too tightly across the top of the foot can directly compress and irritate the extensor tendons. Improper foot strike while running or training on inclined surfaces, which demands greater toe-lifting, can also overload the tendons.
Acute Injuries and Underlying Systemic Conditions
Extensor tendonitis is not always the result of gradual wear and tear; it can be triggered by a single, sudden event or stem from internal body processes. An acute injury, such as a direct blow to the hand or foot, or an unexpected sprain, can immediately damage the extensor tendon fibers. This sudden trauma causes immediate inflammation and pain, bypassing the slow progression of overuse.
Systemic diseases also increase susceptibility to extensor tendon irritation by promoting widespread inflammation. Rheumatoid arthritis, an autoimmune disorder, can target the lining surrounding the tendons (tenosynovium), causing inflammation that mimics tendonitis. Gout, another inflammatory condition, can deposit uric acid crystals into the tendon tissues, leading to painful irritation.
In rare cases, specific medications can compromise tendon integrity. The class of antibiotics known as fluoroquinolones, including ciprofloxacin and levofloxacin, increases the risk of tendon problems and rupture. These drugs are thought to affect the metabolism of tendon cells, potentially causing the breakdown of collagen and weakening the tissue.