De Quervain’s tenosynovitis is caused by inflammation of the tendons that run along the thumb side of the wrist, specifically the abductor pollicis longus (APL) and extensor pollicis brevis (EPB) tendons. These tendons pass through a narrow tunnel called the first dorsal compartment, and when they become irritated or inflamed, the sheath around them thickens and restricts smooth movement, leading to pain and swelling near the base of the thumb.
The primary cause of this inflammation is **overuse or repetitive strain** of the thumb and wrist. Activities that involve frequent gripping, pinching, lifting, or twisting motions—especially those that require the thumb to move away from the hand or extend—can repeatedly stress these tendons. This chronic overuse causes friction within the tight tunnel, leading to irritation, swelling, and eventually tenosynovitis.
Common scenarios that often lead to this condition include:
– **Repetitive hand and wrist motions** such as texting, typing, or using a computer mouse extensively.
– **Lifting or carrying heavy objects**, especially with the thumb extended upwards, like lifting a child or heavy bags.
– **Occupational tasks** that require frequent thumb movements, such as gardening, knitting, or assembly line work.
– **Sports activities** involving gripping or wrist twisting, like golf or racket sports.
– **New mothers** frequently develop De Quervain’s tenosynovitis due to the repetitive lifting and holding of their babies, combined with hormonal changes that may affect tendon sheaths.
Besides overuse, other factors can contribute to the development of De Quervain’s tenosynovitis:
– **Anatomical variations**: Some people have a naturally narrower first dorsal compartment tunnel, making the tendons more prone to irritation.
– **Inflammatory conditions**: Diseases like rheumatoid arthritis can cause inflammation in the tendon sheaths.
– **Injury or trauma**: Direct injury to the wrist or thumb can trigger inflammation.
– **Hormonal changes**: Pregnancy and postpartum periods are linked to increased risk, possibly due to fluid retention and hormonal effects on connective tissues.
The inflammation causes the tendon sheath to thicken and sometimes develop nodules, which restrict tendon gliding and cause a characteristic “sticking” or catching sensation when moving the thumb. This leads to pain that can be sharp or aching, often worsening with thumb and wrist motion, especially when pinching or grasping objects. Swelling and tenderness are common near the base of the thumb, and sometimes the pain radiates up the forearm. In some cases, there may be a feeling of weakness or numbness due to irritation of nearby nerves.
In summary, De Quervain’s tenosynovitis results from repetitive or sustained thumb and wrist movements that cause friction and inflammation of the tendons passing through a tight anatomical tunnel. This inflammation leads to pain, swelling, and difficulty moving the thumb, often triggered by overuse, certain activities, anatomical factors, or hormonal changes.
