Ulnar nerve dislocation (at elbow)

Last revised by Yuranga Weerakkody on 26 Dec 2021

Ulnar nerve dislocation (or it if occurs to lesser degree ulnar nerve subluxation) at the elbow is an uncommon cause of pain and paresthesia in the ulnar nerve distribution. It occurs if the ulnar nerve subluxes and then dislocates over the anterior aspect of the medial epicondyle during flexion and extension of the elbow. 

Ulnar nerve dislocation to thought to occur in around 16% of normal individuals 1 with hypermobility reported in as much as 37% of normal individuals 8.

As the elbow is flexed or extended, the ulnar nerve dislocates over the anterior aspect of the medial epicondyle. A "snap" may be heard or felt. This motion may eventually result in ulnar neuropathy with characteristic pain and paresthesia along the ulnar nerve distribution.

Some suggest the probable cause being a congenital laxity of supporting ligaments 4.

A subluxed nerve can be more vulnerable to injury than normally positioned nerves.

Ulnar nerve dislocation is separate entity from snapping triceps syndrome, which is more uncommon. The nerve may dislocate in snapping triceps syndrome as well.

Ultrasound is the imaging modality of choice since it can dynamically image the relationship between the ulnar nerve and medial epicondyle during elbow flexion and extension.

To evaluate 2-3:

  • the transducer is placed transversely over the medial epicondyle, over the entrance to the cubital tunnel
  • the patient flexes the elbow
    • there is normally some movement of the ulnar nerve toward the apex of the medial epicondyle
    • dislocation occurs if there is translation of the ulnar nerve over the medial epicondyle
    • a snap may be heard or felt with the movement
  • evaluation of the ulnar nerve distal to the neuropathy may reveal a swollen and hypoechoic nerve, characteristic ultrasound findings in ulnar neuropathy.
  • ulnar neuropathy may be seen on standard elbow MRI, but a diagnosis of ulnar nerve dislocation can only be suggested with elbow MR in both the flexed and extended positions

Possible differential considerations include

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Cases and figures

  • Case 1: on ultrasound
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  • Case 2: ultrasound with cine loop
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