Table 2.

Main Characteristics of the Included Systematic Reviews

Author	Type	Topic	Outcome Measures	Results	Limits	AMSTAR
Alsubheen et al (2019)34	Systematic review (8 RCT) 225 patients	-Mobilization techniques Exercises -Electrotherapy -Patient education -Corticosteroid injection -MUA -Suprascapular nerve block	VAS, ROM, SPADI, CSS, ASES, SST	Very low-quality evidence that a combination of physiotherapeutic interventions can improve shoulder function and ROM	-Heterogeneity of the interventions. -No agreement on a univocal rehabilitation protocol. -Duration of the intervention not specified.	8/11
Blanchard et al (2010)35	Systematic review (6 RCT) 407 patients	Corticosteroid injections alone or with physiotherapeutic interventions: -passive/active mobilizations -active exercise -strengthening exercise -electrotherapy	VAS, ROM, SPADI, SDQ	-Corticosteroid injections have greater effect in the short term compared with physiotherapeutic interventions -Both physiotherapeutic interventions and corticosteroid injections alone were more effective than the control groups	They selected RCTs that did not include a precise staging of the disease nor a control group.	7/11
Eljabu et al (2018)36	Systematic review of 6 articles (retrospective study, case series and RCT) 786 patients	Intra-articular injections of cortisone and stretching exercise programs	CSS, SST, VAS, DASH, ROM	Standardized non-operative treatment programs are an effective alternative to surgery in most cases	Low quality of the selected articles and the differences among treatment protocols	5/11
Favejee et al (2011)37	Systematic review (18 RCT) Pz?	-Oral steroids -Steroid injection -Physiotherapy -Acupuncture -Suprascapular nerve block	ROM, VAS	-Strong evidence for the efficacy of laser therapy and steroid injections for the treatment of FS pain in the short term -Moderate evidence in favor of short- and long-term mobilization techniques and medium-term steroid injections for ROM recovery -Moderate evidence was highlighted for the effectiveness of relaxation alone and in addition to active physiotherapy in the short term -Moderate evidence in the short term was found for the effectiveness of oral steroids	Lack of an unambiguous definition of frozen shoulder Differences in the selection criteria Heterogeneity of the interventions	7/11
Grant et al (2013)38	Systematic review of 22 articles (case series and retrospective cohort studies) 1000 patients	- MUA -Arthroscopic capsular release	ROM	No clear difference in shoulder ROM or patient-reported outcomes when comparing a manipulation under anesthesia to an arthroscopic capsular release	Low-quality of the evidence provided.	7/11
Jain et al (2014)39	Systematic review (39 articles) Pz?	-LLLT -High-grade posterior Mobilization -Mobilization-with- movement -Occupational therapy -Continuous passive motion -Cyriax approach -US	VAS, ROM, CSS, DASH, ASES, HAQ, SF-12, SDQ, SPADI, SRQ	-Therapeutic exercises and mobilization are strongly recommended for reducing pain, improving ROM and function in patients with stages 2 and 3 of frozen shoulder. While high grade posterior mobilization along with self exercises is recommended for improving passive external rotation and abduction ROM, high grade mobilization and mobilization with movement along with self exercises are recommended for improving function. -Low-level laser therapy is strongly suggested for pain relief and moderately suggested for improving function but not recommended for improving ROM.	Methodological limitations: only 12 studies were considered high quality, the results must be viewed in perspective of the good methodological quality of the individual studies	5/11
Lowe et al (2019)40	Systematic review (30 articles) Patients?	-Joint mobilization and upper extremity cycle ergometer vs ultrasound and exercises -Static progressive stretching plus multimodal intervention vs multimodal intervention -Shortwave diathermy, passive mobilization, and home exercise -Intra-articular corticosteroid injections	VAS, ROM, SPADI, ASES	High-grade mobilization may be more effective than low-grade mobilization	Only 4 trials were evaluated as being at low risk of bias	7/11
Noten et al (2016)41	Systematic review (12 articles) 810 patients	-High-intensity techniques beyond the pain threshold -Cyriax approach -Mulligan technique -Maitland technique -Angular mobilization, translational mobilization -Spine mobilizations combined with glenohumeral stretching and both angular and translational mobilization	VAS, LIKERT	-Mobilization techniques have beneficial effects -The Maitland technique and spine mobilizations combined with glenohumeral stretching and both angular and translational mobilization seem to be recommended	-High risk of bias of the articles examined -The studies were overly heterogeneous.	5/11
Page et al (2014)29	Systematic review (19 articles) 1249 patients	-LLLT -PEMF -US -Phonophoresis -Shortwave diathermy -Interferential current	SPADI, ROM, VAS, CSS	LLLT plus exercise for 8 weeks appears more effective than exercise alone in terms of pain and function.	Lack of information about patient’s follow-up	10/11
Page et al (2014)42	Systematic review (32 articles) 1836 patients	-PNF -Mulligan technique -Maitland technique -TENS -Cyriax approach -Stretching -MUA -Anterior and posterior glide mobilizations -Bare-handed exercises -Dumbbell exercises	VAS, SPADI, ROM	A combination of manual therapy and exercise may not be as effective as corticosteroid injection in the short-term	Lack of information about patient’s follow-up	9/11
Saha et al (2019)43	Systematic review (2 articles) 100 patients	US either alone or in combination with non-electrotherapeutic treatment/s	ROM, VAS	It is hard to unequivocally state that the continuous mode of US treatment is beneficial in improving the ROM	-Lack of large multicentric well-conducted RCT -Sample too small	5/11
Sun et al (2016)44	Systematic review (9 RCT) 214 patients	-Steroid injection Phisiotherapy, such as -Active glenohumeral motion -Extracorporeal shockwave therapy -Ice and hot pack, ultrasound -PNF -Transcutaneous electrical nerve stimulation -ROM exercises -Maitland technique -Stretching -Codman exercises -Infrared irradiation	SPADI, ROM, VAS, SDQ	Steroid injections are more effective in the management of related disability, while physiotherapy treatment in ROM improvement	Heterogeneity among the analyzed studies	7/11
Tedla et al (2019)45	Systematic review (10 articles) 403 patients	PNF techniques	SPADI, ROM, SST, VAS	PNF is superior in decreasing pain and reducing disability, increasing ROM, and improving function	Heterogeneity among the analyzed studies	7/11
Uppal et al (2015)46	Systematic review (9 articles) 419 patients	-Physiotherapy -Both oral and intra articular steroid -Hydrodilatation -MUA -Arthroscopic capsular release	OSS, VAS, LIKERT, CSS, ASES	It cannot be determined which is the most effective treatment.		5/11

Abbreviations: RCT, randomized controlled trial; MUA, manipulation under anesthesia; VAS, Visual Analogue Scale; ROM, range of motion; SPADI, Shoulder Pain and Disability Index; CSS, Constant-Murley Shoulder Score; ASES, American Shoulder and Elbow Surgeon score; SST, Simple Shoulder Test; SDQ, The Shoulder Disability Questionnaire; DASH, Disability of the Arm, Shoulder and Hand scale; LLLT, low-level laser therapy; US, ultrasound therapy; HAQ, The Health Assessment Questionnaire Disability Index; SF-12, The Short Form (12) Health Survey; SRQ, The Shoulder Rating Questionnaire; LIKERT, Likert scale; PEMF, Pulsed Electromagnetic Field Therapy; PNF, Proprioceptive Neuromuscular Facilitation; TENS, Transcutaneous Electrical Nerve Stimulator; OSS, Oxford Shoulder Score.