A few years ago I got into an interesting conversation with a colleague about the importance of static posture in patients with impingement syndrome (SIS). She was convinced that the literature showed that posture was an important factor in subjects with SIS and I had a different perspective. After this conversation I started doing some poking around in the literature. As I put more and more time into this endeavor, and was unable to find a literature review on the topic, I decided to write one. This review was recently published in Physical Therapy Reviews and I encourage you to take a look.
After lots of searching and reading I found 9 articles which looked at posture in subjects with SIS. All 9 of these studies found no connection between SIS and posture. To make sure I was thorough I included 15 other studies which provided information on the subject but did not specifically look at self- selected resting posture in subjects with SIS. For example, they may have looked at asymptomatic subjects, subjects with neck/shoulder pain or non self-selected postures. These 15 studies had mixed results with 9 of them providing some support for the plausibility of a connection between SIS and posture. For example, Borstad et al found a relationship (in asymptomatic subjects) between pectoralis length and scapular mechanics similar to those seen in subjects with SIS. In a subsequent article they connected pectoralis length with postural findings such as kyphosis and scapular internal rotation. These two studies suggest a mechanism by which posture and SIS could be connected, however this connection has never been demonstrated in a symptomatic population.
To continue in my attempt to be thorough, I also included 7 studies which looked at treatments aimed at postural correction. Of those seven, only one looked specifically at postural correction in subjects with SIS. This study found that postural correction increased pain free ROM but did not change overall pain levels. The problem with this study is that they did not differentiate between shoulder complex motion and simply increased elevation due to contributions of thoracic extension. So it is possible that the subjects’ shoulders did not move more, rather they simply got more apparent elevation due to thoracic motion. There were 3 studies which indicated that exercise can have an effect on posture, however it is unclear if the changes were meaningful or long lasting.
Since finishing the search for my article, two additional noteworthy articles have been published on the topic. Both of these studies have the same lead author, Filip Struyf from Belgium. This study published in Int J Sports Med is the first prospective study I have found on the topic. This study followed 113 overhead athletes for 2 years and 25 (22%) of them developed shoulder pain. Baseline measurements of scapular dyskinesis, protraction, upward rotation, dynamic scapular control and acromial distance were not predictive of future shoulder pain. The second study published in Clin Rheumatol looked at stretching and motor control exercises versus stretching, muscle friction and eccentric cuff exercises for treatment of SIS. The group that performed the motor control exercises had the most improvement, however these improvements were not associated with changes in scapular measurements (upward rotation, forward shoulder posture, strength, motor control or pec minor length). This suggests that although the motor control exercises may have been helpful, their effect was not due to changes in posture or motor control.
Despite this lack of evidence for a connection between posture and SIS, there still seems to be strong beliefs in and out of our profession about the importance of posture. If we look at SIS as a disorder caused by abnormal mechanical pinching it does make a lot of sense that certain postures could increase this pinching. However, if we look at SIS as a more complex disorder that may not be strongly associated with pinching, it becomes easier to understand why posture may not play a large role in this disorder.