Cubital tunnel syndrome (CTS) is a common nerve entrapment. The ulnar nerve alongside the outside of the elbow travels down and around the elbow in a trough or tunnel called the cubital tunnel. Pressure on the nerve from inside or outside the tunnel can cause painful symptoms. Numbness, tingling, and weakness of the hand and fingers are also common.
Doctors aren't sure the exact cause of CTS. It could be increased pressure by the wall of the cubital tunnel affects the nerve. It could be stretching of the nerve itself. Perhaps both factors occur together. A few studies have shown increased pressure from the angle of the elbow. Increased elbow flexion decreases the amount of space in the tunnel for the nerve.
A recent study from Japan suggests compression from outside the tunnel is part of the problem. During surgery for eight patients with CTS they measured the pressures inside the cubital tunnel. Pressure was measured at three separate locations with the elbow in two different positions.
The results of this study support the idea that pressure inside the tunnel affects the nerve and leads to CTS. Surgery to move the nerve away from the tunnel is advised.