Physical Therapists often assess and compare scapular kinematics in individuals who present with shoulder pathology. We do this to develop a reference of movement for the “painful” limb. But in this practice, have you ever considered if scapular movement is truly “symmetrical” prior to pathology? A recent article published in Manual Therapy compared the 3-D scapular kinematics of dominant and non-dominant shoulders in “healthy” individuals and the results are quite interesting.
The researchers studied 14 young adults (13 right handed) who volunteered for inclusion. Each of the participants denied having upper quadrant pain over the past six months nor participated in asymmetric overhead sporting activities on a regular basis. The researchers utilized electromagnetic tracking to track and register the positioning and orientation of several sensors applied to the upper extremity. Kinematic data was then taken to assess scapular behavior during shoulder movements.
According to the researchers, this study showed that during rest and with activity (shoulder abduction), scapular positioning differs between dominant and non-dominant arms. ie. Side-to-side differences likely exist in healthy shoulders. But this isn’t the only study to demonstrate this—the authors cite several others and claim:
“The observation of asymmetric scapular positioning in this study was not surprising, given that most kinematic investigations demonstrated side-to-side differences in scapular position and motion of healthy populations”.
These findings are quite important to the practicing Therapist. We often assess symmetry at rest and with movement, but what does it really tell us? I would love to hear your thoughts….
Morais NV, Pascoal AG. Scapular positioning assessment: Is side-to-side comparison clinically acceptable? Manual Therapy 2013: 18; 46-53