The ulnar collateral ligament is a complex structure comprising three bands which run proximal to distal from the medial epicondyle to the ulna.
The main component and that most often injured is the anterior band.
Occasionally plain films will demonstrate a spur at the sublime tubercle, a sign of chronic traction.
Coronal fat saturated intermediate images are the most useful for diagnosis.
Full thickness tears are more common than partial thickness tears.
The precise location of injury depends on the population under study.
Much of the literature in North America relates to tears at the ulnar insertion.
This is principally due to the prevalence of throwing sports particularly baseball which is practiced from a young age.
In other populations humeral attachment and mid substance tears are more common.
The ulnar collateral ligament has its proximal insertion deep and distal to the common flexor origin.
The distal attachment is to the sublime tubercle of the ulna.
Like the collateral ligaments of the knee, the external relation is fat, consequently on fat saturated images any fluid lateral to the collateral ligament should be regarded with suspicion.
The ligament should also been a well demarcated low signal line between its insertions
Partial thickness tears have been well described in the literature most commonly at the ulnar insertion.
Many injuries involve the deep surface of the ligament which may become separated from the underlying ulna.
The injury is best appreciated by MR arthrography where contrast is seen to extend around the margin of the ulna, deep at the ligament.
Contrast extending more than 2-3mm should be regarded as abnormal and indicative of a partial tear,
although such a finding is more common in the older asymptomatic population.
Contrast extending around the margin of the ulna forms an appearance which has been likened to a ‘T’ lying on its side and hence this is sometimes referred to as the T sign.
Lower grade injuries can also be detected as fluid lying medial to the ulnar collateral ligament with intact fibres.
Several other entities are associated with ulnar collateral ligament tear.
One of these is termed poster medial impingement or valgus extension overload syndrome.
This is an impingement injury of the medial aspect of the olecranon against the lateral aspect of the posterior portion of the medial epicondyle.
It arises as a consequence of excess motion related to laxity of incompetence of the ulnar collateral ligament.
Boxing is a common sporting association
