The direct answer to whether carpal tunnel syndrome (CTS) causes fingers to lock up is no. This confusion highlights the difference between two distinct hand conditions. Carpal tunnel syndrome is a nerve disorder resulting from the compression of the median nerve as it passes through the narrow passageway in the wrist called the carpal tunnel. This compression causes symptoms related to nerve function, such as numbness and weakness, rather than a mechanical restriction of movement. The locking sensation is a symptom of a different pathology involving the tendons and their sheaths.
Classic Symptoms of Carpal Tunnel Syndrome
The symptoms of carpal tunnel syndrome stem directly from the median nerve being squeezed within the wrist. This nerve compression causes numbness and a “pins and needles” sensation in the areas the median nerve supplies: the thumb, index finger, middle finger, and the thumb-side half of the ring finger. The little finger is unaffected because the ulnar nerve provides its sensation.
Symptoms often develop gradually and tend to worsen at night, frequently waking the person who needs to shake out the hand for relief. As the condition progresses, muscle weakness and atrophy can occur. This weakness is noticeable in the thenar muscles at the base of the thumb, making fine motor tasks like buttoning a shirt or gripping small objects difficult. The discomfort felt with CTS is typically described as a deep ache, pain, or burning sensation in the wrist and hand that can sometimes radiate up the forearm.
The Real Cause of Finger Locking
The sensation of a finger catching, clicking, or locking in a bent position is caused by Stenosing Tenosynovitis, commonly called Trigger Finger. This is not a nerve problem but involves the mechanical gliding of a tendon. Flexor tendons, which control the bending of the fingers, pass through a series of fibrous tunnels, or pulleys, that keep them close to the bone.
Trigger finger occurs when the flexor tendon or its protective sheath becomes inflamed and thickened, often forming a small nodule. The tendon’s path is then constricted, especially at the entrance of the A1 pulley, located at the base of the finger in the palm. When the finger attempts to straighten, this thickened section gets stuck trying to pass back through the narrowed pulley, causing the characteristic catching or locking. The finger may then suddenly snap straight with an audible click.
How Carpal Tunnel and Trigger Finger Differ
The difference between carpal tunnel syndrome and trigger finger lies in the anatomical structure affected. Carpal tunnel syndrome is a compressive neuropathy involving the median nerve within the wrist, which affects sensation and muscle control.
Trigger finger, conversely, is a form of tenosynovitis, which is an inflammation of a tendon and its sheath. This condition affects the mechanical movement of the finger, causing physical snagging or locking. Despite their distinct pathologies, these two conditions are sometimes confused because they both cause pain and dysfunction in the hand and wrist. They can also occur simultaneously in the same person, often due to shared underlying risk factors like diabetes or rheumatoid arthritis.
Diagnosis and Treatment Options
Diagnosis is obtained through a physical examination and medical history. For carpal tunnel syndrome, a doctor may perform specific tests to check for median nerve irritation, and a nerve conduction study is often used to confirm the degree of nerve compression. Trigger finger diagnosis is typically made through a clinical exam, where the physician can feel the catching or a tender nodule at the base of the affected finger.
Treatment options for both conditions initially focus on non-surgical approaches. For carpal tunnel syndrome, conservative measures include wearing a wrist splint, particularly at night, and sometimes corticosteroid injections to reduce inflammation around the nerve. Trigger finger is often treated with rest, splinting to keep the finger extended, or a corticosteroid injection directly into the tendon sheath to decrease swelling. If conservative treatments fail to provide lasting relief, surgical intervention may be recommended. This involves releasing the ligament in CTS or cutting the A1 pulley in trigger finger to relieve the underlying obstruction.