The diagnostic label of subacromial impingement syndrome is a common diagnosis of shoulder pain and was introduced by Neer1 in 1972. Subacromial impingement syndrome is an “umbrella” term that encompasses a number of pathoanatomic alterations in patients with similar clinical presentation.2 Considering the aforementioned, rotator cuff related shoulder pain (RCRSP) has been proposed as a more adequate term for painful conditions attributed specifically to the rotator cuff.3 Although it is now suggested that the use of special and provocative tests for the diagnosis of RCRSP should be abandoned,4 these tests are still commonly used in clinical practice.5

Patients with RCRSP typically present with pain during active elevation of the arm. The “painful arc” is considered a hallmark sign of RCRSP, and has been classically described to occur between 60° and 120° of arm elevation.6 However, the presence of pain below and above the “painful arc” is often seen clinically. The source of pain during arm elevation is unknown but is often presumed to be caused by compression of the subacromial structures.7 Several investigations have assessed the impact of humeral elevation on subacromial proximities.8 Studies generally report minimal acromiohumeral distance to occur in the range of 70° to 120° of arm elevation.9 But, this metric does not reflect proximity to the rotator cuff tendons as it is a bone-to-bone measurement. Other studies have identified the smallest distances between the insertion of the rotator cuff tendons and the coracoacromial arch to occur at lower angles of arm elevation, between 40° and 758–11

This calls into question if the “painful arc” is useful to help clinicians during clinical management in patients with shoulder pain. While for some individuals most activities of daily living or work (such as cooking, making the bed, typing, driving, washing the floor, cleaning surfaces, gardening, etc.) are performed at lower ranges of arm elevation, for others, many daily professional activities (such as washing walls and windows, brick laying, painting walls and ceilings, etc.) are performed at higher levels of arm elevation. Therefore, it is possible that people who experience the onset of pain at different ranges of arm elevation may have distinct functioning of the upper limbs. Demographic characteristics (e.g. age) and clinical characteristics (e.g. chronicity of symptoms) of the condition may also impact upper extremity functioning to some extent.12 The clinical presentation and functioning of patients with shoulder pain may be affected by several factors that occur with both aging and duration of symptoms, such as shoulder degenerative alterations,13,14 strength decline,12 and high relative effort during functional tasks.12 Information regarding other possible clinical and demographic contributors to upper extremity disability may provide a better understanding of the evaluation and decision-making processes for treating individuals with RCRSP.

The objectives of this study were to: 1) determine and characterize the association between the angular onset of pain during arm elevation and upper-limb self-reported functioning, 2) verify whether demographic and clinical characteristics contribute to this association, and 3) investigate whether these characteristics differ considering distinct ranges of angular onset of pain in individuals with RCRSP.

The characteristics of the participants and between-group comparisons are presented in Table 1. A total of 252 individuals were included in the study. Dunn post-hoc analysis revealed a substantial difference in age between the 60° – 120° and the >120° groups (median difference: −5 years; 95%CI: −8, −1). Majority of the individuals (65.4%) presented angular onset of pain above 120° of arm elevation, 31.7% presented angular onset of pain between 60° - 120° of arm elevation and 2.8% below 60° of arm elevation (Fig. 1).

Fig. 1.

Distribution of the participants according to the Disabilities of arm, shoulder and hand (DASH) score and angular onset of pain during arm elevation. Orange circles: <60°; Blue triangles: 60° - 120°; Green squares: >120°. The bold blue line indicates the regression line estimated for the data. The gray area represents the standard error of the regression line.

(0.16MB).

Considering the comparison of DASH score between each category of the angular onset of pain, the score was lower in individuals with angular onset of pain above 120° of arm elevation when compared to those with the onset of pain between 60° – 120° (median difference: −10.8 points; 95%CI: −15.0, −6.7). There was no difference between the other categories (Fig. 2).

Fig. 2.

Boxplots from Disabilities of arm, shoulder and hand (DASH) score and the angular onset of pain during arm elevation in individuals with rotator cuff related shoulder pain.

(0.14MB).

The relationship between the angular onset of pain and the DASH score was further analyzed using a stepwise multivariable linear regression. Table 2 shows that 31% (Adjusted R2 = 0.30) of the variance in the final model was explained by male sex, age, the dominant side affected, duration of symptoms, and the angular onset of pain during arm elevation.

The results of this study demonstrated that most individuals with RCRSP presented with an angular onset of pain above 120° of arm elevation in the sagittal plane, and similar functioning as the few participants with angular onset of pain below 60°. Male sex, lower age, non-dominant side being affected, and longer duration of symptoms were found to be associated with better functioning as assessed by the DASH score. These variables were able to explain only 31% of DASH score variance.

Greater disability was observed in individuals with the angular onset of pain between 60° – 120° of arm elevation in the sagittal plane. It is worthy to highlight that most activities assessed in the DASH questionnaire and most daily activities22 are performed in this range of motion. A recent study has suggested that the DASH questionnaire may not be appropriate to assess individuals with RCRSP who have onset of pain at higher ranges of arm elevation.23 This is because ceiling effect occurred in most individuals with the angular onset of pain above 120° of arm elevation.23 Clinicians should be careful when interpreting the DASH in individuals with RCRSP and pain above 120° of arm elevation in the sagittal plane.

Individuals with the angular onset of pain above 120° showed similar functioning as the few individuals with the angular onset below 60°. Interestingly, those are the ranges that put the supraspinatus tendon in closer contact to the glenoid (above 120°) and coracoacromial arch (below 60°).24 In our study, most individuals presented the angular onset of pain above 120° of arm elevation in the sagittal plane. Saini et al.24 demonstrated that deformation of the supraspinatus tendon against the glenoid occurred more frequently than against the coracoacromial arch. This is interesting data. Although we cannot make direct comparison, as compression may not be the source of pain or related to functioning, the current study may also suggest that individuals with RCRSP are more likely experiencing internal rather than subacromial impingement. Finally, these data call into question whether the “painful arc” is not being precisely described or is not representing RCRSP.

When using a stepwise multivariable linear regression, sex and dominance of the affected side were the most associated to the DASH score. However, these results should be interpreted with caution because the contribution of each covariate to the DASH score reaches the standard error of the measurement (4.6 points), but does not reach the minimum detectable change (10.8 points) of the DASH for individuals with upper-extremity musculoskeletal disorders.25 Being a man decreases the DASH score by 9.5 points, which means that men present better functioning than women. Cultural and occupational factors may contribute to explain this finding. One conceivable factor may be the presence of sex imbalance in domestic work.26 Women are more likely to look after the house, even if they have a full-time job, performing activities such as cleaning, cooking and others, adding to their everyday jobs and possibly overloading the shoulder over time. Physiological factors may also be considered, as men are capable to produce more strength27 and likely contribute to the findings.

In addition, according to the model obtained, having the non-dominant side affected also decreases the DASH by 6.15 points. When completing the DASH individuals rate their ability to complete specific activities regardless of which arm is used to perform them.28 However, many activities (e.g. opening a tight or new jar, writing, changing a light bulb overhead, etc.) are likely to be performed with the dominant side. As such, involvement of the dominant limb possibly leads to greater DASH total scores, i.e., greater disability. In contrast, Christiansen et al.29 have demonstrated that the side of the symptoms does not influence the DASH total score in individuals with rotator cuff disorders, but does influence the score by about 20% for some specific activities of the 30 items of the DASH.29 Therefore, clinicians are encouraged to look at individual activities of the DASH, and not only rely on the total score to seek possible influence of the affected side.

Age (young age - better functioning) and duration of symptoms (longer duration - better functioning) provided less important contributions to the DASH variance. This might be explained by the inclusion of mostly young adults, and of individuals with chronic symptoms (equal or greater than 6 months). Individuals experiencing persistent shoulder pain seem to have no signs of shoulder pain related to biomechanical impairments,30 and may have developed a compensatory strategy to cope with their own condition, which may justify the better use of the upper limb in daily activities. Further studies should consider a wider range of age and inclusion of individuals in the acute stage of the condition (less than 6 months) and also of other variables such as psychosocial factors like kinesiophobia and fear avoidance, for example.

The choice of the DASH questionnaire to assess functioning of the upper extremities in these individuals may have influenced the results of this investigation. Further studies should assess the influence of the angular onset of pain during arm elevation on functioning by using questionnaires more specific to the shoulder, such as the Shoulder Pain and Disability Index (SPADI) and the Western Ontario Rotator Cuff (WORC) Index. Future research should also include more individuals with the angular onset of pain below 60° to further clarify their functional abilities and limitations. Furthermore, adding variables related to psychological components (kinesiophobia, fear-avoidance, and pain catastrophizing) and other clinical measures (muscle strength, for example) commonly used to assess patients with RCRSP to the model may lead to a better explanation of the DASH variance and should be included in future studies. Our findings should not be generalized to all planes of arm elevation. Although the “painful arc” was originally described in the frontal plane, elevation of the arm is also commonly assessed in the scapular and sagittal planes in clinical practice as most of our activities are performed between these planes. Finally, clinicians should consider exercises addressing functional limitations of daily living activities because these are most compromised in patients with RCRSP and angular onset of pain between 60° and 120°.

The angular onset of pain during arm elevation in the sagittal plane is associated to self-reported functioning of the upper limbs in individuals with RCRSP. Individuals with RCRSP and angular onset of pain above 120° of arm elevation present better functioning than individuals with onset of pain between 60° and 120°, and similar functioning as those with onset of pain below 60°. Male sex, lower age, non-dominant side being affected, and longer duration of symptoms are also associated to better functioning as assessed by the DASH questionnaire. Most of the individuals with RCRSP presented the angular onset of pain above 120° of arm elevation, suggesting internal impingement.