Investigations of Abnormal Scapular Kinematics During Humeral Elevation in Subjects With Shoulder Impingement or Rotator Cuff Tendinopathy

1Associate Professor, Program in Physical Therapy, Department of Physical Medicine and Rehabilitation, The University of Minnesota, Minneapolis, MN. 2Doctoral Graduate, Program in Rehabilitation Sciences, Department of Physical Medicine and Rehabilitation, The University of Minnesota, Minneapolis, MN; Co-owner, Reynolds Rehab Physical Therapy, Minneapolis, MN. Address correspondence to Dr Paula M. Ludewig, Program in Physical Therapy, MMC 388, 420 Delaware St SE, Minneapolis, MN 55455. E-mail: Ludew001@umn.edu houlder pain and associated glenohumeral joint movement dysfunctions are common and debilitating conditions.12,84,117 The most frequently occurring problems include shoulder impingement and associated rotator cuff disease or tendinopathy, which can progress to rotator cuff tears,24,84 as well as glenohumeral joint instability and adhesive capsulitis. With the exception of adhesive capsulitis, the majority of these shoulder complaints are related to The pathogenesis of rotator cuff tendinopathy is not precisely known and is somewhat controversial; however, a multifactorial etiology is likely.81,106 Proposed mechanisms include (1) anatomic reductions in the available space beneath the coracoacromial arch or within the supraspinatus outlet area leading to subacromial impingement,129 (2) intrinsic tendon degeneration from eccentric overload, ischemia, aging, or inferior tissue properties,106 and (3) scapular or humeral movement alterations compromising the rotator cuff tissues through subacromial or internal impingement.84 There is evidence in an animal model for eccentric overuse, or eccentric overuse combined with reduced available subacromial space (subacromial impingement), as a factor resulting in the development of rotator cuff tendinopathy.106 Such factors are likely of greatest interest to physical therapists, as rehabilitation programs are often directed at correction of posture or movement deviations believed to reduce the subacromial space, or directed at improvement of tissue properties through stretching and strengthening. Regardless of initial etiology, movement deviations that further compromise the subacromial space or contribute to internal impingement are presumed undesirable in the presence of a rotator cuff or long head of the biceps tendinopathy. The majority of rotator cuff tears are believed to be a progression of cumulative trauma from occupational or athletic activities that involve frequent use of the arm at, or above, shoulder level. The point prevalence of shoulder pain in certain sports or occupations can reach 40% or higher.31,41,68 Shoulder impingement has been defined as compression, entrapment, or mechanical irritation of the rotator cuff structures and/or long head of the biceps tendon either beneath the coracoacromial arch (subacromial) or between the undersurface of the rotator cuff and the glenoid or glenoid labrum (internal). Repetitive impingement is one of multiple proposed mechanisms for the development of rotator cuff disease, as well as progression to partial or full-thickness rotator cuff tearing.87,106