Acquired and adaptive changes in the throwing athlete: implications on the disabled throwing shoulder.

The throwing shoulder continues to be one of the most actively studied and poorly understood aspects of sports medicine. The act of throwing itself transfers tremendous power throughout the kinetic chain, resulting in forces experienced in the shoulder that can exceed its physiologic limits. These forces over time lead to many adaptive changes in the bone, capsule, and muscular structures of the shoulder girdle. An understanding of these acquired changes is critical to differentiate between normal or protective adaptation and pathologic change. The purposes of this article were to elucidate the adaptive and acquired changes, which commonly develop in the throwing shoulder, to explain how these changes contribute in both protective and pathologic roles, and to apply these principles into a deeper understanding of the care of the disabled throwing shoulder.