At the elbow, the ulnar nerve (UN) may be the site of a static compression (by the cubital tunnel retinaculum and Osborne's ligament between the two heads of the flexor carpi ulnaris), or a dynamic compression, especially when the nerve is unstable (subluxation/dislocation outside the ulnar groove). The clinical basis for the diagnosis of ulnar neuropathy involves looking for subjective and objective signs of sensory and/or motor deficit in the ulnar nerve's territory in the hand, a pseudo-Tinel's sign, and doing manipulations to provoke UN irritation. The diagnosis is confirmed by electromyography and ultrasonography. In the early stages, patient education and elimination of flexion postures or repeated elbow flexion motions can provide relief. If this fails or signs of sensory and/or motor deficit are present, surgical treatment is proposed. If the nerve is stable, in-situ nerve decompression is typically done as the first-line treatment. If the nerve is unstable, anterior nerve transposition – generally subcutaneous – or more rarely, a medial epicondylectomy can be done. If surgical treatment fails, the patient's history is reviewed, and diagnostic tests can be repeated. Except in cases of a fibrotic scar, the main causes of failure are neuroma of a branch of the medial cutaneous nerve of the forearm, instability of the nerve and persistence of a compression point. In the latter two cases, surgical revision is justified and anterior nerve transposition or epicondylectomy can be proposed.