Imaging sports related elbow injuries. Windows Vista Icons In Xp. Elbow instability is a looseness in the elbow joint that may cause the joint to catch, pop, or slide out of place during certain arm movements. It most often occurs. Ulnar Collateral Ligament Elbow Physical Therapy' title='Ulnar Collateral Ligament Elbow Physical Therapy' />The medial and ulnar collateral ligaments maintain the stability of the elbow. A tear in either of these ligaments can occur when stress is applied to the.