Shoulder impingement syndrome is one of the most common causes of shoulder pain, which is one of the most common musculoskeletal disorders [1]. Shoulder impingement or shoulder pain syndrome is the painful entrapment of the soft tissues between the acromion and the humeral head [2]. It could be caused either by narrowing of the shoulder outlet or thickening of its contents (supraspinatus tendon, subacromial subdeltoid bursa, joint capsule, etc.) [3]. The one-month prevalence of shoulder pain is between 16 and 30% [4]. Mainly there are two types of causes of shoulder pain syndrome, either there will be a reduction in the subacromial space or thickening of the contents of the shoulder outlet (supraspinatus tendon, glenohumeral ligaments, and subacromial subdeltoid bursa) [5]. For the evaluation of shoulder impingement syndrome, Neer and Hawkins tests are being used for a long. However plain X-ray, computed tomography, magnetic resonance imaging and ultrasound are being used for its evaluation as imaging modalities [6].

Dynamic sonography is progressively being used for the evaluation of shoulder impingement syndrome [7]. The moment of the supraspinatus and subacromial subdeltoid bursa could be observed in real-time while passing underneath the acromion during arm abduction [8]. No other imaging modality can evaluate structure in real-time during a physiologic moment [9, 10]. The sensitivity and specificity of ultrasound are high enough to be used as a gold standard for the assessment of shoulder impingement syndrome [7, 11]. Dynamic ultrasound proved as a helpful tool in the detection of various abnormalities of the painful shoulder especially impingement syndrome [12]. In cases of full-thickness tear, the sensitivity and specificity of ultrasound are very high 100% and 97%, respectively, whereas slightly low in partial-thickness tears [13]. The reproducibility of the radiation-based modalities is better, however, having a high potential for bioeffects [14]. In contrast to other imaging modalities, ultrasound is a non-invasive, inexpensive, readily available, relatively quick procedure, with no special preparation required, and safe for the diagnosis of musculoskeletal disorders [15, 16]. However, sonoelastography has been increasingly used to investigate musculoskeletal disorders [17].

The severity of the shoulder impingement syndrome is linked with the range of shoulder moment restrictions. Therefore, the severity of the shoulder impingement syndrome is classified in different severity grades ranging from Grade-0 to Grade-3. Neer classification of shoulder impingement was done as: acute inflammation, edema, hemorrhage in the rotator cuff in patients younger than 25 years was termed as Grade-1, fibrosis, and tendinitis of the rotator cuff usually between 25 and 40 years was termed as Grade-2, while mechanical disruption of the rotator cuff tendons, changes in the coracoacromial arch and osteophytes along the acromion in patients more than 40 years was Grade-3 [4]. The management plane of the shoulder impingement syndrome is generally based on the degree of functional disturbance, and the extent of structural damage [18, 19]. In the current study, the interobserver agreement is checked on the degree of functional disability categorized into four grades.