Home / Conditions / Cubital tunnel syndrome
The ulnar nerve — the one you hit when you catch your funny bone — runs through a shallow groove behind the elbow. When it is compressed there, the little and ring fingers go numb.
The same nerve can be compressed at the elbow, at the wrist, or where it leaves the neck, and the symptoms overlap. One question separates them better than any other: is the back of the hand numb as well as the palm side? The branch supplying the back of the hand leaves the nerve well above the wrist, so it escapes anything trapping the nerve at the wrist itself.
| Cubital tunnel at the elbow | Guyon’s canal at the wrist | Nerve root at the neck | |
|---|---|---|---|
| Back of the hand | Numb as well | Normal | Often numb, and further up the forearm too |
| What provokes it | A bent elbow — sleeping, phone calls, leaning on a desk | Pressure on the palm — cycling, tools, a crutch | Neck movement, coughing, straining |
| Where it aches | Inner elbow and along the inner forearm | The hand only | Down from the neck and shoulder blade |
| Tapping the funny bone | Sends a shock to the little finger | No effect | No effect |
| Weakness pattern | Grip and finger spreading, sometimes the ring and little fingers curling | Finger spreading, with feeling often intact | Can include muscles above the hand |
This is a different nerve from the one in carpal tunnel syndrome. If the thumb, index or middle fingers are the numb ones, the problem is almost certainly not here — see carpal tunnel syndrome instead. The two can occur in the same arm, which is worth examining for rather than assuming.
At the elbow the ulnar nerve sits in a shallow groove behind the bony bump on the inner side, covered by little more than skin and a band of tissue. There is no muscle over it. That is why knocking it is so memorable, and why resting the elbow on an armrest or a car door presses directly on a nerve.
What a picture cannot show is what happens when the elbow bends. The groove flattens and narrows, and the nerve is stretched around the outside of the joint at the same time. Hold the elbow bent for hours — asleep, or with a phone to your ear — and both effects add up.
This explains the pattern people describe: waking with a dead hand, symptoms during a long call, nothing much during the day. It is also why the first treatment is about elbow position rather than medication.
Wasting is the finding that changes the timetable. When the muscle between the thumb and index finger has visibly hollowed, the nerve has been under pressure long enough to lose fibres. Sensation often recovers after that; the muscle bulk frequently does not. It is the one finding that turns a watch-and-wait into a decision.
Most people improve without an operation, and the first steps are about keeping the elbow straighter rather than taking anything.
Not resting it on desks, armrests or car doors; using a headset instead of holding a phone; raising the chair so the elbow sits more open at a keyboard. Simple, and enough on its own for a fair number of people.
The elbow curls up during sleep whatever you intend, so a splint holding it loosely straight is the single most useful thing for night symptoms. A towel wrapped round the elbow and taped does the same job if a splint is uncomfortable. An elbow pad helps where the problem is pressure rather than bending.
Where symptoms persist or the muscle is weakening, the nerve is given more room. That may mean releasing the tissue over the groove, or moving the nerve to the front of the elbow so it is no longer stretched when the joint bends. Which one depends on the examination — particularly whether the nerve slips out of its groove — and on what is narrowing the space.
Night symptoms and aching usually settle first. Numbness improves more slowly and may not go entirely, and strength takes months rather than weeks. Operating before the muscle wastes gives the best chance of a full recovery, which is the reason not to leave it indefinitely.
It is the same nerve. The funny bone shock is what happens when the ulnar nerve is struck directly, because it lies just under the skin behind the elbow with no muscle protecting it. Cubital tunnel syndrome is that nerve under steady pressure rather than a single knock.
The elbow bends during sleep, which both narrows the groove and stretches the nerve around the joint. Hours in that position is enough to bring on numbness, and it is why a night splint often helps more than anything taken by mouth.
No. Carpal tunnel affects the median nerve at the wrist and the thumb, index and middle fingers. This is the ulnar nerve at the elbow and the little and ring fingers. Both can be present in the same arm, so it is worth checking rather than assuming.
Mild cases often do, particularly once the elbow stops being bent or leant on for long stretches. What does not reliably recover is muscle that has already wasted, which is why persistent numbness is worth assessing rather than waiting out.
Most people do not. Surgery is considered when symptoms persist despite splinting and changing elbow position, when the numbness has become constant, or when the muscles are weakening.
No. Bring any nerve conduction study or X-ray reports, and a note of which fingers are affected and whether the back of the hand is numb too.
Carpal tunnel syndrome · Radial tunnel syndrome · Tennis elbow · Cervical radiculopathy · Neuropathic pain · Wrist pain
Be ready to say which fingers go numb, and whether the back of the hand is numb as well. That one answer narrows it considerably.
