The carpal tunnel is a narrow passageway on the palm side of your wrist, about the width of your thumb. When the median nerve running through this tunnel gets compressed, the result is carpal tunnel syndrome, a condition affecting roughly 5% of the global population. It causes numbness, tingling, and weakness in specific fingers of the hand.
The Anatomy of the Carpal Tunnel
Your wrist bones form a curved floor and walls, with a tough band of tissue called the flexor retinaculum acting as the roof. The bones forming the boundaries include the scaphoid and trapezium on the thumb side, and the pisiform and hook of the hamate on the pinky side. This creates a rigid channel with very little room to spare.
Nine tendons pass through this tunnel, all responsible for bending your fingers and thumb. The median nerve travels alongside them in a shallow position just beneath the roof of the tunnel, sitting on top of the tendons that control your index and middle fingers. Because the tunnel is surrounded by bone and rigid ligament, there’s no way for it to expand. Any swelling inside the tunnel puts pressure directly on the nerve.
What Happens to the Nerve Under Pressure
Even mild compression changes how the median nerve functions. At low pressures, tiny blood vessels inside the nerve start losing flow, which starves nerve fibers of oxygen. Slightly more pressure disrupts the nerve’s internal transport system, the mechanism that moves nutrients and signals along the length of the nerve fiber. At higher levels of compression, the protective insulation around nerve fibers (called myelin) begins to distort and break apart.
This damage doesn’t require a sudden injury. A persistent, low-grade increase in pressure causes fluid to leak from blood vessels inside the nerve, creating swelling that raises the pressure even further. It becomes a self-reinforcing cycle: compression causes swelling, swelling increases compression, and the nerve progressively loses its ability to send clear signals to your hand. That’s why symptoms often start mild and worsen over months or years.
Who Gets Carpal Tunnel Syndrome
Women develop carpal tunnel syndrome at significantly higher rates than men, making up about two-thirds of all cases. The condition peaks in adults over 40, though it can appear at any age. A large study of over one million people in Taiwan found that rheumatoid arthritis carried the strongest association with carpal tunnel syndrome, followed by gout, high blood pressure, diabetes, obesity, and kidney disease. In younger adults under 40, underactive thyroid and vitamin B6 deficiency were additional risk factors, and the relative impact of all these conditions was stronger in the younger group.
Pregnancy is another common trigger, likely because of fluid retention that increases pressure in the tunnel. Repetitive wrist motions, particularly in combination with forceful gripping, can contribute as well, though the relationship between keyboard use and carpal tunnel syndrome is less straightforward than many people assume.
How Carpal Tunnel Syndrome Feels
The hallmark symptom is numbness and tingling in the thumb, index, middle, and ring fingers. The little finger is not affected, because it receives its nerve supply from a different nerve entirely. This distinction is one of the most reliable clues that the median nerve is the source of the problem.
Many people first notice symptoms at night, waking up with a numb or “pins and needles” sensation and shaking their hand to restore feeling. This happens because most people sleep with their wrists bent, which narrows the tunnel further. Over time, the tingling may appear during the day, especially while gripping a steering wheel, holding a phone, or doing any activity that keeps the wrist flexed. In advanced cases, the muscles at the base of the thumb can weaken and visibly shrink, making it harder to grip objects or pinch things between your thumb and fingers.
How It’s Diagnosed
A doctor can often identify carpal tunnel syndrome through two simple physical tests. Phalen’s test involves holding your wrists in a fully flexed position for 60 seconds. If this reproduces your tingling or numbness, it correctly identifies carpal tunnel syndrome about 85% of the time. Tinel’s sign, where the doctor taps over the nerve at the wrist, is slightly less sensitive at 62% but highly specific at 93%, meaning a positive result strongly suggests the diagnosis.
When the diagnosis is uncertain or surgery is being considered, a nerve conduction study measures how quickly electrical signals travel through the median nerve. Slower-than-normal conduction across the wrist confirms compression and helps determine severity.
Treatment Without Surgery
For mild to moderate cases, a wrist splint worn at night is the first line of treatment. The splint holds your wrist in a neutral position, preventing the flexion that compresses the nerve while you sleep. Research shows that six weeks of nighttime splinting produces meaningful improvement in symptom severity and nerve function. Extending splinting beyond six weeks did not provide additional benefit in clinical studies.
Corticosteroid injections into the carpal tunnel can reduce inflammation and provide temporary relief, often lasting weeks to months. These are particularly useful for people whose symptoms are related to a temporary condition like pregnancy. Activity modification, including reducing repetitive gripping or sustained wrist flexion, can also slow progression.
Ergonomic Adjustments That Help
If you work at a desk, keyboard positioning matters more than most people realize. Cornell University’s ergonomics guidelines recommend placing your keyboard below seated elbow height, with the back edge of the keyboard tilted slightly away from you. This keeps your wrists in a neutral position rather than bending them upward, which is what happens with most standard keyboard setups that tilt toward the user. A slightly reclined sitting posture with your elbows at an open angle promotes better blood flow to the forearms and hands.
When Surgery Is Needed
If symptoms persist despite conservative treatment, or if nerve conduction studies show significant damage, carpal tunnel release surgery is the definitive treatment. The procedure cuts the ligament forming the roof of the tunnel, permanently relieving pressure on the nerve. Two approaches exist: open surgery, which uses a small incision in the palm, and endoscopic surgery, which uses one or two tiny incisions and a camera.
Both methods produce equivalent long-term outcomes. At three months and beyond, grip strength, sensation, and pain scores are the same regardless of technique. The differences are in early recovery. Patients who undergo the endoscopic approach return to work an average of 6 to 8 days sooner, and they experience better grip strength, pinch strength, and hand dexterity in the first three months. Scar sensitivity and wound complications like infection and scar tenderness are also less common with endoscopic surgery.
Serious complications are rare with either method. In a meta-analysis of nearly 28,000 cases, structural damage to nerves, arteries, or tendons occurred in 0.19% of endoscopic surgeries and 0.49% of open procedures. Endoscopic surgery does carry a slightly higher rate of temporary nerve irritation (1.45% vs. 0.25%), though these episodes resolve on their own. Overall patient satisfaction tends to be higher with the endoscopic approach.
What Recovery Looks Like
Most people can return to desk work or light daily activities within one to two days after surgery. Jobs that involve physical labor typically require a few weeks before full duty is possible. Returning to sports, heavy lifting, or gym workouts generally takes four to six weeks. Numbness and tingling often improve quickly after surgery, sometimes within days, though full nerve recovery can take longer depending on how compressed the nerve was before the procedure. People who had severe, long-standing symptoms may not recover complete sensation, which is one reason earlier treatment tends to produce better outcomes.