Cubital tunnel syndrome is an entrapment neuropathy, or nerve compression syndrome, a condition caused by compression, traction or friction, of the ulnar nerve at the elbow. Nerve compression is also known as a trapped nerve. The ulnar nerve travels from the shoulder down the length of the arm to the hand. Along its course it may become compressed at several sites. At the elbow the ulnar nerve passes through the cubital tunnel. Ulnar nerve compression most commonly occurs at the level of the cubital tunnel. The ulnar nerve provides motor and sensory innervation to the forearm, and hand and its compression can cause the numbness and other symptoms associated with cubital tunnel syndrome. In many cases the cause is unknown.