Shoulder impingement/instability overlap syndrome.

Impingement syndrome is one of the most common shoulder problems seen by the orthopedist. Multidirectional instability is less common but can present with impingement symptoms. Patients having impingement symptoms due to multidirectional instability have a syndrome called "impingement/instability overlap." The purpose of this study is to retrospectively review 50 consecutive patients with a condition we have coined "impingement/instability overlap" syndrome. We discuss the criteria, by history and by physical examination, for inclusion in this category and the results of treatment. Our study shows that when the primary cause (instability) is treated with rehabilitation and/or surgery, the secondary symptoms, impingement and pain, can be alleviated. Conversely, if subacromial decompression is done to treat the secondary impingement, the primary symptoms, instability and pain, persist. Instability should be considered the primary etiology in any patient having impingement symptoms, especially in the younger patient (< 35 years old). Rehabilitative and surgical treatment should address the pathologic instability.