This is a common term used for shoulder pain. Shoulder impingement in itself is not a diagnosis, but a syndrome that refers to a specific presentation of shoulder symptoms and signs which are the results of various conditions.
The term impingement refers to catching or rubbing. In the shoulder, this applies to pain that originate as a result of rubbing of the shoulder tendons (the rotator cuff) against the tip of the shoulder blade (acromion).
Shoulder impingement is common in middle aged men but can occur in women too. It usually presents with spontaneous onset of pain over the shoulder or in the upper arm. This pain is worse when raising the arm to the side, over-head or when reaching backwards. Patients may sometimes have pain at night too. Weakness and stiffness may also be a feature.
Conditions that lead to narrowing of the space between the tendons and the acromion will present with impingement syndrome. These conditions include acromial bony spurs, osteophytes from an arthritic acromio-clavicular joint (ACJ), rotator cuff tendon tears, calcific tendonitis, labral (cartilage) tears, instability, etc. It is important to identify the cause when planning treatment.