Impingement is a term used to describe the pain associated with a pinching of tissue underneath the acromial process of the scapula (shoulder blade) when the arm is raised above the shoulder. It classically affects older people, over the age of 50, with underlying arthritis, but can occur in younger people who have a pronounced hook shape to their acromion. Classic impingement gets worse with time and leads to swelling of the underlying bursa called bursitis.
Pain when the arm is used overhead is the classic symptom and typically becomes worse with more activity.
The doctor will begin by performing range of motion tests. If motion is restricted, the doctor may inject lidocaine to see if the pain is eliminated or lessened. The reduction in pain results in a positive impingement test. To confirm these results, the doctor may perform an ultrasound or MRI. Sometimes the doctor will use x-rays to see if a bone spur is present.
Workers and athletes who repetitively perform overhead movements should warm up and strengthen their shoulder muscles with proper exercises. Learning about the warning signs of early impingement may help to prevent additional tissue damage.