Impingement is the compression and irritation of tissue as it travels through a bony space in your shoulder called the subacromial space. The tissues that travel through this space include bursa, rotator cuff tendons, biceps tendon, and ligament.It often causes pain on the front or side of your shoulder, especially when the arm is elevated. This condition may also be diagnosed according to which tissue is affected, ie. rotator cuff. Your therapist will assess your shoulder and create a treatment plan to resolve your symptoms.