The ulnar nerve is one of the three large nerves that crosses the elbow (the others are the median and radial nerves). The ulnar nerve passes across the elbow on the medial (inside) side. It lies very near to the medial ulnar collateral ligament. As it crosses the elbow joint, it enters a small tunnel referred to as the cubital tunnel. This tunnel is made up of bone on one side and ligament on the other. Because this space is tight, it is a common place where the nerve can become compressed. This compression is often referred to as “cubital tunnel syndrome,” and it can lead to nerve-related problems such as pain, weakness, numbness, and even muscle atrophy.  

While nerve compression is one cause of ulnar nerve symptoms, nerve instability (meaning the tunnel is too loose and the nerve moves more than it should) can also cause similar symptoms.