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Rady Children's Specialists

Elbow Instability (Medial Ulnar Collateral Ligament Injury)

Instability, or looseness, of the elbow is the result of an injury to the ulnar collateral ligament, or UCL. The UCL is on the inner side of the elbow and attaches the bump  (medial epicondyle) of the arm bone to the bigger of the two forearm bones (ulna).

This ligament is most commonly injured in throwing athletes but can be injured in any athlete that uses the elbow to bear weight (wrestling or gymnastics) or who has sustained an elbow dislocation. The injury is uncommon in patients who are still
growing (because injury to the growth plate is more common) but can occur.


Symptoms of elbow instability include:

  • Pain on the inner side of the elbow with throwing or pushing up from a seated position.
  • Swelling at the elbow.
  • A sense of looseness when bearing weight on the elbow.
  • Decrease in ability to throw the ball as fast or as accurately.


Symptoms, athletic (throwing) history, and an exam of the elbow will most likely  lead to the diagnosis. X-rays can rule out a fracture, but an MRI will be important to  assess the ligaments and look for loose bodies in the joint. The MRI should be done
with dye to better assess the structures in the elbow joint (including the UCL).


Treatment of an UCL injury can be conservative if the tear is incomplete. This  involves stopping all throwing (including any throwing outside organized sports) and  resting the elbow. Physical therapy may improve the strength of the muscles around
the elbow.

A complete tear, or a partial tear that does not respond to conservative treatment,  usually requires surgery. Another option is to stop baseball or the offending sport, as  this type of elbow instability usually does not affect daily activities. If stopping  playing is not a viable option, reconstruction of the ligament can be performed – this  procedure is known colloquially as the “Tommy John” surgery. If you decide to have  the surgery, you will need to refrain from pitching for a year. Many people who have  the surgery make a successful return to pitching.