Extensor tendonitis is a condition characterized by inflammation or irritation of the extensor tendons. Tendons are strong, fibrous cords that connect muscles to bones, facilitating movement. Extensor tendons specifically enable the straightening of fingers, the extension of wrists, and the lifting of toes and the front of the foot. These tendons are commonly found on the back of the hands, wrists, and the top of the feet. When these tendons become irritated, they can swell and cause pain, making everyday movements difficult.
Primary Mechanisms of Injury
Extensor tendonitis primarily develops through two fundamental pathways: overuse and repetitive strain, or sudden acute injury. Overuse and repetitive strain involve cumulative stress on the tendons over time. Repeated motions or sustained activities can lead to microscopic tears within the tendon fibers. This accumulation of tiny injuries overwhelms the tendon’s natural healing capacity. The continuous stress results in irritation and inflammation, causing the tendon to swell and become painful.
While inflammation is often present, chronic tendon issues may involve degeneration of the tendon tissue, a condition sometimes referred to as tendinosis or tendinopathy. In tendinosis, the collagen fibers within the tendon can deteriorate, becoming disorganized and less effective at transmitting force. This degenerative process can occur even without significant inflammation.
Conversely, extensor tendonitis can also arise from a sudden or acute injury. This might include a direct impact, a sudden forceful movement, or an unaccustomed load placed on the tendon. For example, jamming a finger can cause the thin extensor tendons to rip from their bone attachment. Such acute incidents can immediately damage the tendon tissue, leading to pain and dysfunction.
Activities and Contributing Factors
Many specific activities and pre-existing conditions can increase the likelihood of developing extensor tendonitis. Repetitive activities are a leading cause, as they place continuous stress on the extensor tendons. Common examples include prolonged typing or using a computer mouse, playing musical instruments like the piano or guitar, and engaging in sports that involve repetitive hand or foot movements such as tennis, golf, baseball, or running. Occupations requiring sustained standing, walking, or manual labor like gardening, landscaping, woodworking, or painting also frequently contribute to the condition.
Improper technique or poor ergonomics significantly increase tendon strain. Incorrect posture, such as prolonged sitting in the same position, or poorly designed workspaces can place undue stress on tendons in the wrist and hand. For instance, a non-ergonomic keyboard can contribute to extensor tendonitis in the hands, while ill-fitting or excessively tight shoes can irritate extensor tendons on the top of the foot.
Inadequate warm-up or conditioning before physical activity also plays a role in injury development. Starting exercises or sports without properly preparing muscles and tendons can increase the risk of strain and injury. A proper warm-up increases blood flow and muscle temperature, making tendons more pliable and less susceptible to tears. Weak supporting muscles or a sudden increase in activity level without gradual progression can also overload tendons.
Certain equipment, or a lack thereof, can contribute to tendonitis. Poorly fitted shoes, especially those with tight lacing that press down on the top of the foot, are a common factor for ankle extensor tendonitis, particularly in activities like dancing, running, skiing, and skating. Similarly, using old or inappropriate sports equipment can increase risk.
Anatomical or biomechanical issues can predispose individuals to extensor tendonitis. Natural variations in foot structure, such as flat feet or high arches, can place additional strain on foot tendons. Underlying medical conditions can also impact tendon health, making them more vulnerable to injury. These include autoimmune diseases like rheumatoid arthritis, certain types of arthritis such as gout or osteoarthritis, and metabolic conditions like diabetes or thyroid disorders. Tendons can also become less elastic and more susceptible to injury with age, as changes in collagen production and organization within tendons lead to decreased flexibility and a slower healing capacity.