The Popping Elbow / Unstable Elbow / Elbow Posterolateral Instability

The Popping Elbow

Some patients complain of elbow instability.

Elbow instability is a “looseness” in the elbow joint that may cause the joint to catch, jam, pop, or slide out of place during certain arm movements.

It most often occurs as a result of an injury ā€” typically, a previous elbow dislocation.

This type of injury can damage the bone and ligaments that surround the elbow joint and work to keep it stable.

What is LUCL?

The lateral collateral ligament (LCL) complex of the elbow joint consists of:

  • the annular ligament
  • the radial collateral ligament
  • the lateral ulnar collateral ligament (LUCL)

elbow-ligament-reconstruction-1 (1)

The radial collateral ligament originates from the lateral epicondyle and terminates indistinguishably in the annular ligament, which stabilizes the proximal radioulnar joint.

The LUCL originates from the lateral epicondyle, blending with fibers from the annular ligament but arching superficial and distal to it.

This ligament is the primary restraint to varus stress and is deficient in posterolateral rotatory instability of the joint.

Injury to the LUCL causes Posterolateral Rotatory Instability of the Elbow

Posterolateral rotatory instability of the elbow is a three-dimensional displacement pattern of abnormal external rotatory subluxation of the ulna coupled with valgus displacement on the humeral trochlea.

  • This pattern causes the forearm bones to displace into external rotation and valgus during flexion of the elbow.
  • Injury to the lateral ulnar collateral ligament allows abnormal supination of the ulna on the humerus.
  • The radial head, being locked in the sigmoid (radial) notch of the proximal ulna by the annular ligament, subluxates posterior to the capitellum.
  • The abnormality is usually posttraumatic and presents with locking, snapping, clicking, catching, and recurrent dislocation of the elbow.

An easier way to understand it is to see this video:

The patient often complains of difficulty pushing off and out of a chair using the affected upper limb.


MRI scans can help to show the ligament injury:


LCL Elbow Injury LUCL Injury 1


Surgical treatment involves reconstructing the LUCL ligament. I use the hamstring tendon to do this procedure:



For more information of this injury and treatment, please contact Dr HC Chang at +65-683 666 36 or email us at

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