While in PT school, most of us were made aware of faulty movement patterns we might exhibit. Our professors used us as examples to demonstrate patterns that we could expect to see on patients in the real world. Scapular dyskinesia, knee valgus, overpronation, and many other movement "faults" were often highlighted in ortho lab. By graduation, we became faulty-movement snipers--adept at spotting compensations or imbalances, not only in the controlled environment of the PT clinic but also out in the world. Gathering, grouping, and interpreting information from watching the way people move is essential to our profession’s unique approach to healthcare and guides the way we treat.
Learning to observe
One memorable instance of learning to look for faulty movements involved my friend Brian. During a ther-ex lab, one of our professors noticed that he exhibited a motion not dissimilar to this:
Soon, the whole class was gathered behind Brian, oohing and ahhing at his scapular dyskinesia. Brian, understandably, was concerned. Unable to even see his own scapulae, he must have imagined something grotesque to cause such a reaction from our eager-to-learn class. Determined not to live with such an affliction, it thereafter became common to observe Brian performing scapular depressions and serratus punches for hours at the gym.
Let’s take a step back
I use Brian’s dyskinesia and his subsequent obsession with it as an example of how our education, although producing the desired effect of training us to pick up signs, can also render us myopic to the purpose and nature of an examination finding.
When examining a patient's faulty movement patterns, I find it helpful to consider these 3 questions:
- How related is a phenomenon to a given pathology?
- What is the nature of this relation (correlation, causation, and which direction if causal)?
- Is treating the phenomenon beneficial in treating the pathology?
How many people with shoulder pain actually have scapular dyskinesia?
One would think that the most basic question would be the easiest to answer, but in fact, there is a dearth of published epidemiological data that has investigated the co-incidence of scapular dyskinesia and shoulder pain. The population studied may influence the estimated rates. In one study following 246 high school baseball players, the injury rate in the throwing arm was actually lower in subjects with identified scapular dyskinesia, which was described as either subtle or obvious using a video analysis method.
Conflictingly, a study using the same classificatory method on 206 professional handball players found a significant association between “obvious” scapular dyskinesia and shoulder injury, but only a non-signficant effect with “subtle” dyskinesia. A study following 120 rugby players also found a significant correlation between both previous injury and current pain, but used the Kibler classification.
Chicken or egg?
The classic assumption is that scapular dyskinesia is a risk factor or a direct cause of shoulder injury, although more recent scapular summits and surveys of experts are more reluctant to define the directionality of the relationship. The baseball, rugby, and handball studies described above were all prospective, with a scapular assessment performed at baseline and injuries tracked over one or more seasons. As described above, their disparate findings and heterogeneity do little to elucidate a causal role of scapular dyskinesia in shoulder injuries. Regrettably, scapular assessments in subjects that got injured, but previously had normal scapular movement, were also not performed or reported.
The ethical concerns of inducing pain have obviously precluded the testing of the hypothesis that shoulder pain can cause dyskinesia. Two studies hypothesized that the removal of pain via the injection of an anesthetic into the subacromial space would normalize scapular kinematics in subjects with subacromial pain compared to control groups consisting of matched healthy subjects and the opposite (non-painful) side, respectively.
Counterintuitively, both studies actually yielded results in which scapular dyskinesia increased following the removal of pain (and, it should be noted, likely the removal of any sensation from the subacromial space). Specifically, both cohorts ended up demonstrating significantly increased scapular anterior tilt and one of them resulted in increased scapular internal rotation as well.
What is the treatment effect of scapular exercises?
Given the complex relationship between scapular dyskinesis and shoulder pain, how important is it that we include treatments intended to fix scapular mechanics with shoulder patients? Is there clear evidence that the tools Brian and my classmates were given to address this problem even work?
There is certainly enough evidence published to justify the inclusion of scapular-focused treatment. Scapular-focused treatment, in general, is successful at producing clinically meaningful improvements in pain and function. There is also evidence suggesting a significantly greater treatment effect than just modalities. However, in another study which compared scapular strengthening exercises to modalities and light ROM, there was no significant difference between the groups with pain.
If a treatment approach that includes or emphasizes correcting scapular movement is effective at reducing patients’ shoulder pain, one would expect a corresponding reduction in scapular dyskinesia. However, results from the handful of studies that measure kinematics and/or muscular activation of the scapula are conflicting. While a case-control study found a normalization of both posterior tilt, upward rotation, and serratus activation after a 10-week motor control program, an RCT and a cohort study--both with larger populations--found that scapular exercises actually increased anterior tilt or resulted in no change in scapular movement, respectively.
Conclusion
The appeal for “more methodologically sound studies” has become a truism in literature reviews, but the lack of evidence to support the notion that scapular dyskinesia is a feature, cause, or an impairment to be corrected in shoulder pain is a valuable conclusion in itself. At the very least, it is a good example of how we shouldn’t overestimate our finely-tuned observation skills without careful consideration of the relationship between a phenomenon and a pathology. My own weighing and interpretation of the research has had the additional effect of me choosing not to perform a test (i.e. screening for scapular dyskinesia) if it won’t influence the way I treat.
References
Myers JB, Oyama S, Hibberd EE. Scapular dysfunction in high school baseball players sustaining throwing-related upper extremity injury: a prospective study. J Shoulder Elbow Surg. 2013;22(9):1154-9.
Clarsen B, Bahr R, Andersson SH, Munk R, Myklebust G. Reduced glenohumeral rotation, external rotation weakness and scapular dyskinesis are risk factors for shoulder injuries among elite male handball players: a prospective cohort study. Br J Sports Med. 2014;48(17):1327-33.
Kawasaki T, Yamakawa J, Kaketa T, Kobayashi H, Kaneko K. Does scapular dyskinesis affect top rugby players during a game season?. J Shoulder Elbow Surg. 2012;21(6):709-14.
Ettinger L, Shapiro M, Karduna A. Subacromial Injection Results in Further Scapular Dyskinesis. Orthop J Sports Med. 2014;2(8):2325967114544104.
Worsley P, Warner M, Mottram S, et al. Motor control retraining exercises for shoulder impingement: effects on function, muscle activation, and biomechanics in young adults. J Shoulder Elbow Surg. 2013;22(4):e11-9.
Mcclure PW, Bialker J, Neff N, Williams G, Karduna A. Shoulder function and 3-dimensional kinematics in people with shoulder impingement syndrome before and after a 6-week exercise program. Phys Ther. 2004;84(9):832-48.
Park SI, Choi YK, Lee JH, Kim YM. Effects of shoulder stabilization exercise on pain and functional recovery of shoulder impingement syndrome patients. J Phys Ther Sci. 2013;25(11):1359-62.
Struyf F, Nijs J, Mollekens S, et al. Scapular-focused treatment in patients with shoulder impingement syndrome: a randomized clinical trial. Clin Rheumatol. 2013;32(1):73-85.
