Table 1. Summary of included randomized controlled trials.

Study	Country	Population	Groups	Outcomes	Follow ups	Surgical Interventions	Conservative/No Interventions
Brox 1999 [24]	Norway	Patients with rotator cuff disease for at least three months	Surgery + Ex. n = 45 (29 men, 16 women), Age 48.0 years Exercise n = 50 (22 men, 28 women), Age 47.0 years	-Pain -Function	3, 6 months & 2.5 years.	Arthroscopic surgery (bursectomy and resection of the anterior and lateral part of the acromion and the coracoacromial ligament). Postoperative rehabilitation was started on the first postoperative day. Physiotherapy was started within the first week. The exercises prescribed by the surgeon were performed against low resistance and repeated many times. Patients visited a physiotherapist where they lived, so several physiotherapists were engaged, and somewhat different approaches used. Unrestricted activities were usually allowed after four to six weeks.	To eliminate gravitational forces and to start the exercises the arm was suspended in a sling fixed to the roof. Relaxed repetitive movements (first rotation, then flexion—extension, and finally abduction-adduction) were performed for about an hour in a daily training session. Patients were supervised twice weekly. On the other days they followed the same exercise programme at home. Resistance was added gradually to strengthen the short shoulder rotator and the scapular stabilising muscles. The training continued for three to six months, with the supervision gradually being reduced.
Rahme 1998 [25]	Sweden	Patients with subacromial impingement syndrome	Surgery + physiotherapy n = 21 Physiotherapy n = 18 (19 males, 23 females), age 42.0 years	-Pain	6 months & 1-year.	Open anterior acromioplasty according to Neer. Attention was paid to the portion of the acromion that may extend beyond the anterior border of the clavicle. Followed by physiotherapy.	Information on functional anatomy/ biomechanics, advice on how to avoid wear and tear positions, unload movements of the shoulder, normalize scapulohumeral rhythm, postural awareness, strengthening of the shoulder muscles and endurance training.
Haahr 2005; 2006 [26–27]	Denmark	Patients with subacromial impingement	Surgery + Physiotherapy n = 41 (12 males, 29 females), Age 44.3 years Physiotherapy n = 43 (14 males, 29 females) Age 44.5 years	-Pain -Function	3, 6 months, 1 year, & 4–8 years.	The treatment consisted of bursectomy with partial resection of the antero-inferior part of the acromion and the coracoacromial ligament. Two experienced surgeons undertook all procedures and recorded their findings on a predetermined proforma. Before discharge, the patient was instructed in performing light movements of the arm within the limits of pain. Stitches were removed by general practitioners after 10 days. At the same time, the patient was instructed by a physiotherapist to carry out increasingly active exercises, including exercises for strengthening the rotator cuff muscles	The treatments started with application of heat, cold packs, or soft tissue treatments. This was followed by active training of the periscapular muscles (rhomboid, serratus, trapezoid, levator scapulae, and pectoralis minor muscles) and strengthening of the stabilising muscles of the shoulder joint (the rotator cuff). This was done within the limits of pain. During the first two weeks the patient was seen three times weekly, during the next three weeks twice weekly, and during the last seven weeks once weekly. The patients were encouraged to continue to do active exercises at home on a daily basis. After carrying out the full programme for at least 12 weeks, the patients were encouraged to continue the programme two to three times a week.
Ketola 2009; 2013; 2017 [28–29,31]	Finland	Patients with shoulder impingement syndrome	Surgery + Exercise n = 70 (29 men, 41 women) Age 46.4 years Exercise n = 70 (23 men, 47 women) Age 47.8 years	-Pain -Disability	1, 2, 5 & 10 years	Arthroscopic decompressions. An interscalenic or supraclavicular brachial plexus block was applied for regional anaesthesia. Bony landmarks were palpated and marked. Glenohumeral stability and passive range of movement were tested. The arthroscope was introduced through a standard posterior portal and a systematic recording of the articular cartilage, labrum and ligaments, biceps tendon, and the intra-articular rotator cuff was performed. The same standard portal was used to reach the subacromial space. Debridement and decompression were done through an anterolateral portal by shaver and / or vaporiser. If the coracoacromial ligament felt tight or thick, it was released. Acromioplasty was then performed, starting anteriorly and progressing posterolaterally with a burr drill. The range of movement was tested under arthroscopic visualisation to check for any local impingement, plus, similar exercises as the other group. NSAIDs was allowed as needed. Subacromial corticosteroid injections were permitted.	Information was first given by a trained physiotherapist. A home programme was individually planned for each patient according to the same principles. The aim was to restore painless and normal mobility of the shoulder complex and to increase the dynamic stability of the glenohumeral joint (supra- and infraspinatus, teres minor, and subscapular muscles) and the scapula (trapezoid, rhomboid, serratus anterior, and pectoralis minor muscles).29 Elasticated stretch bands and light weights were used in training, which was based on long painless series and repetitions aiming at tendon strengthening. The sessions were performed at least four times a week using nine different exercises with 30 to 40 repetitions three times. As the self-assessed ability and strength improved, resistance was increased, and repetitions diminished. NSAIDs was allowed as needed. Subacromial corticosteroid injections were permitted.
Farfaras 2014; 2018 [11,30]	Sweden	Patients with subacromial impingement syndrome	Open acromioplasty + Physiotherapy n = 15 (7 males, 8 females) age 52.4 years Arthroscopic acromioplasty + Physiotherapy n = 19 (7 males, 12 females) age 48.9 years. Physiotherapy n = 21 (13 males, 8 females) age 49.9 years	-Function	31 months (~2.5 years) & Min. 10 years (range 10–17 years)	Open acromioplasty was performed according to Rockwood and Lyons with the patient in the beach chair position. The procedure started with an anterior, lateral 5-cm skin incision. The deltoid muscle was split and detached from the anterior third of the acromion and the acromioclavicular joint capsule. After exposing the anterior edge of the acromion, the tendinous anterior third of the acromion was elevated dorsally prior to removing bone. This manoeuvre exposed the coracoacromial ligament. An osteotome was used to remove the anterior edge and the lateral portion of the undersurface of the acromion. The removed bone included the attachment of the coracoacromial ligament. The piece of bone was about 6–9 mm wide and 20 mm long. Proximal to the coracoid, the coracoacromial ligament was cut. Palpation of the undersurface of the acromion was performed to detect any fragments of bone or prominences. The undersurface of the acromioclavicular joint was palpated and inspected. If osteophytes were present, they were excised. No acromioclavicular joint resections were performed. Finally, the medial flap of the deltoid was sutured to the capsule of the acromioclavicular joint, and the lateral flap was sutured to the origin of the deltoid before closure of the wound. Arthroscopic acromioplasty was performed according to Ellman with the patient in the lateral decubitus position. A traction device was applied to the arm, and a tension to the arm corresponding to 40 N was applied. The shoulder was in 10° of flexion and 40° of abduction. The bony landmarks of the shoulder (the acromion, the clavicle, the acromioclavicular joint, the coracoid and the coracoacromial ligament) were marked with a pen. A portal for the arthroscope was created on the dorsal side of the shoulder. The gleno-humeral joint was first evaluated for cartilage changes, disorder of the biceps tendon, labrum and the rotator cuff. Using the same arthroscopic portal, the subacromial space was visualised and a bursectomy was performed with a shaver introduced from a lateral portal. A resection of the anterior edge of the acromion of about 5–8 mm was then carried out, followed by a resection of about 5–8 mm of the anterior–inferior third of the undersurface of the acromion all the way to the acromioclavicular joint.	Physiotherapy group received treatments according to the method described by Böhmer. The purpose of the treatment is to let the patients find their normal kinematics of the shoulder, without experiencing pain. The gravitational forces on the arm were removed by suspending the arm in a sling fixed to the ceiling. The training programme started with rotational movements of the arm. As soon as the patient was able to perform these motions without pain, flexion/extension movements were added, followed by abduction/adduction exercises. The training programme postulates everyday practice of at least 60 min. The load was gradually increased in order to strengthen the rotator cuff and the scapula-stabilising muscles. In the final stage of the programme, the patients replaced some exercises with corresponding leisure activities. The programme was performed twice a week under the supervision of a physiotherapist and the rest of the days at home for a period of three to six months. In order to secure similar treatment, all the patients were trained at five local physiotherapy centres by physiotherapists using the same standardised protocol.
Paavola 2018[10]	Finland	Patient with shoulder impingement syndrome	Arthroscopic subacromial decompression + post-operative care including exercise n = 59 (17 males, 42 females) Age 50.5 years Diagnostic arthroscopy (placebo surgery) + post-operative care including exercise n = 63 (17 males, 46 females), Age 50.8 years Exercise Therapy n = 71 (24 males, 47 females) Age 50.4 years	-Pain -Function	3,6 months, 1 & 2 years	Arthroscopic subacromial decompression procedures involved the debridement of the entire subacromial bursa and resection of the bony spurs and the projecting anterolateral undersurface of the acromion, was carried out with a shaver, burr, and / or electrocoagulation. Post-operative care consisted of one visit to an independent physiotherapist, blind to the group assignment, for guidance and instructions for home exercises. Diagnostic arthroscopy involved examination of the glenohumeral joint and subacromial space with the use of standard posterior and lateral portals and a 4 mm arthroscope with the patient under general anaesthesia, usually supplemented with an interscalene brachial plexus block. We did an intraarticular and subacromial assessment of the rotator cuff integrity.	Exercise therapy–Supervised, progressive, individually designed physiotherapy was started within two weeks of randomisation, using a standardised protocol that relied primarily on daily home exercises as well as 15 visits to an independent physiotherapist
Beard 2018 [9]	United Kingdom	Patients with subacromial pain	Arthroscopic subacromial decompression + physiotherapy n = 106 (52 males, 54 females), Age 52.9 years Investigational arthroscopy (placebo surgery) + physiotherapy n = 103 (51 males, 52 females), Age 53.7 years No treatment n = 104 (52 males, 52 females), Age 53.2 years	-Function -Pain	6 and 12 months	Arthroscopic subacromial decompression was done according to routine practice under general anaesthetic. It involved removal of bursa and soft tissue within the subacromial space, release of the coraco-acromial ligament, and removal of the subacromial bone spur through posterior and lateral portals. Investigational arthroscopy (placebo surgery) was also done under general anaesthetic through a posterior portal. Patients underwent routine investigational arthroscopy of the joint, rotator cuff tendons, and subacromial bursa, with the operation done in exactly the same manner as decompression. A lateral skin incision was made to simulate a lateral portal, but no instruments were introduced through this incision. The intervention did not involve surgical removal of any bone, bursal tissue, other soft tissue or release of the coracoacromial ligament. The procedure involved inspection and irrigation of the glenohumeral joint (arthroscopy) and the subacromial bursa (bursoscopy).	No treatment (monitoring) involved patients attending one reassessment appointment with a specialist shoulder clinician, 3 months after entering the study but with no planned intervention. The patients in the no-treatment group had no prescribed physiotherapy or steroid injections.