There usually is an acute onset of moderate to severe lameness during exercise. Horses pulling up lame after a jump or following a stumble are suspect for this problem. Swelling develops fairly quickly in the upper third of the back of the cannon and may appear as swelling around the DDF, making differential difficult from palpation alone. However, injury to the DDF in this region is uncommon.

Occasionally a more insidious onset occurs that improves with rest but worsens with exercise. Swelling is minimal and pain may be difficult to detect. The ICL becomes suspect when nerve blocks eliminate everything from the fetlock down but a high cannon block alleviates the lameness.

In the acute and insidious cases ultrasound will confirm injury to the ICL. The ICL should be compared with the opposite leg and signs of involvement include enlargement, loss of definition of the borders, or hypoechoic or irregular areas within the ligament.

Acute injuries treated with anti-inflammatory therapy, wrapping to control swelling, stall rest, and controlled walking once the acute inflammation subsides for three months have a good prognosis. Though three months may seem like a long time compared with other similar injuries, horses put back to work sooner with confirmed ICL lesions often have recurrence of lameness. Continued work and delay of stall rest may result in further damage with concurrent damage to the DDF or adhesions forming to the surrounding soft tissues and a permanent lameness.