The orthopedic surgeon plays several roles in shoulder rehabilitation. The first is to understand the basic principles of the kinetic chain. The biomechanical model for striking and throwing sports is an open-ended kinetic chain of segments that work in a proximal-to-distal sequence.1,2 The proximal segment contributions are key components of the sequential activation of body segments that is necessary to accomplish any athletic activity. The kinetic chain harmonizes the interdependent segments to produce a desired result at the distal segment. The goal of the kinetic chain activation sequence is to impart maximum velocity or force through the distal segment (the hand) to the ball, racquet, or other implement. The shoulder does not function in isolation but as a link in the kinetic chain activity that optimizes shoulder function. Alterations in any of the kinetic chain links can affect the shoulder, and alterations in the shoulder can affect the other kinetic chain links. The ultimate velocity of the distal segment is highly dependent on the velocity of the proximal segments. The proximal segments accelerate the entire chain and sequentially transfer force and energy to the next distal segment.^2–5 Because of their large relative mass, the proximal segments are responsible for most of the force and kinetic energy that are generated in the kinetic chain.¹ As a result, lower extremity force production is more highly correlated with ball velocity than is upper extremity force production.⁶

This interaction creates two implications for shoulder rehabilitation. First, the evaluation and identification process preceding shoulder treatment and rehabilitation should include more than just local shoulder structures. The evaluation process should result in a complete and accurate diagnosis of all of the altered structures throughout the kinetic chain. Second, optimum restoration of shoulder function requires that all the kinetic chain segment interactions are reestablished to meet the individual’s needs that existed before injury.

The second role of the orthopedic surgeon is to establish the complete and accurate diagnosis of the anatomic, biomechanical, and physiologic alterations that may be present in shoulder injury and dysfunction. This may seem obvious but is sometimes difficult to implement unless the entire kinetic chain is screened for alterations. Nonetheless, the actual shoulder injury is the primary factor that determines treatment and rehabilitation. This may involve tendon injury or tear, instability, or joint internal derangement, whose overt clinical symptoms can be evaluated by standard diagnostic methods. However, both nonovert local and distant alterations are frequently associated with shoulder clinical symptoms and dysfunction.

The most common local alterations are decreased shoulder internal rotation,⁷ which creates altered glenohumeral translations,^7,8 altered strength or strength balance,⁷ and alterations in scapular motion and position (scapular dyskinesis).^7,9–11 Inappropriate scapular motion can disrupt the normal smooth coupling of scapulohumeral movement in voluntary activation and is present in most patients with shoulder impingement. Distant alterations include lumbar muscle inflexibility and muscle weakness,¹² as well as hip and knee inflexibility.¹³ Because these alterations are common findings in shoulder injury, they need to be assessed through a screening process in the clinical evaluation. This requires a clinical evaluation approach known as “victims and culprits,” in which the site of symptoms is the “victim,” but the “culprits” may include alterations at other sites.