Table 1 Characteristics of the included studies

Chiu (2002) [39]; China

Subjects with mechanical neck pain

27.0 (9.5)

12 (57%)

Cibulka (2017) [40]; USA

Healthy adults with mild neck pain gathered through flyers, email, and word of mouth

22.8 (3.5)

23 (62%)

Cleland (2006) [41]; USA

Patients with mechanical neck pain referred to physical therapy at the Rehabilitation Services of a hospital

41 (12.9)

18 (82%)

De Pauw (2020) [42]; Belgium

Patients reporting neck pain, recruitment by advertising on social media and distribution of flyers

28.0 (8.2)

17 (68%)

Dvir (2006) [43]; Israel

Patients injured in whiplash-type accidents

37.1 (9.9)

13 (52%)

Edmondston (2008) [44]; Australia

Subjects with postural neck pain, recruited through poster advertising and through a university physical therapy clinic

36 (11)

14 (67%)

Fletcher (2008) [45]; USA

Subjects with neck pain from a college campus and a community setting

33.6 (10.3)

15 (68%)

Ghorbani (2020) [46]; Iran

Participants with neck pain from the University of Medical Sciences, invited via word of mouth

25.9 (1.04)

13 (65%)

Gonçalves (2019) [47]; Portugal

Individuals with neck pain recruited from a private clinical practice and from the general population

43.6 (13.3)

26 (79%)

Grod (2002) [48]; Canada

Patients with chronic neck pain from two chiropractic offices

38.5 (NA)

11 (58%)

Hanney (2014) [49]; USA

Patients with mechanical neck pain who presented to clinics

48.9 (14.8)

14 (64%)

Harris (2005) [50]; USA

Subjects with neck pain

38 (10)

61%^a

Hoppenbrouwers (2006) [51]; Netherlands

Patients with neck pain from three physical therapy practices

43.0 (10.9)

15 (60%)

Hoving (2005) [52]; Netherlands

Patients with neck pain, referred by general practitioners for physical therapy

45.5 (9.2)

20 (63%)

Kristjansson (2004) [53]; Iceland

Female patients with chronic whiplash (grades I or II of Quebec Task Force classification) recruited from physiotherapy clinics

30.0 (8.8)^a

10 (100%)

Kristjansson (2010) [54]; Iceland

Subjects with non-traumatic neck pain

38.0 (8.3)

11 (61%)

Kumbhare (2005) [55]; Canada

Patients with WDA (grade II of Quebec Task Force classification) recruited from a hospital

39.9 (14.9)

49 (69%)

Law (2013) [56]; China

Patients with neck pain from the out-patient Physiotherapy Department of a hospital

44.52 (7.11)

17 (65%)

Lourenço (2016) [57]; Portugal

Students with idiopathic neck pain from a university

20.18 (1.84)

17 (77%)

Majcen Rosker (2021) [58]; Slovenia

Patients with chronic neck pain, referred by an orthopaedic surgeon

46.2 (4.8)

23 (72%)

Martins (2018) [59]; Portugal

Participants with neck pain recruited from the general population

36.8 (2.4)

28 (85%)

Murphy (2010) [60]; New Zealand

Subjects with chronic neck pain recruited through advertisements in local papers and word of mouth

44.8 (8.5)

11 (79%)

O'Leary (2005) [61]; Australia

Subjects with neck pain recruited by printed and electronic advertising within the University

27.9^a

75%^a

Pearson (2009) [62]; Canada

Patients with WAD recruited from a rehabilitation and return-to-work program and from advertisements in local newspapers

36.6 (10.8)

6 (43%)

Peolsson (2007) [63]; Sweden

Patients with chronic neck disorders from primary care and from private clinicians

intra-rater: 49 (11); inter-rater: 47 (8)

intra-rater: 9 (90) ; inter-rater: 6 (75)

Petersen (2000) [64]; USA

Subjects with present complaints of local cervical pain

40.2 (8.7)

13 (65%)

Piva (2006) [65]; USA

Patients referred to a University Spine Speciality Centre with a primary complaint of neck pain

41 (12)

18 (60%)

Pourahmadi (2018) [66]; Iran

Subjects with non-traumatic neck pain recruited by purposive and snowball sampling

31.12 (6.38)

20 (50%)

Rheault (1992) [67]; USA

Subjects with a history of cervical spine pathology

37.41 (14.1)

15 (68%)

Röijezon (2010) [68]; Schweden

Women with non-traumatic neck pain recruited by advertising in local papers and by information to job holders

48 (7)

16 (100%)

Roren (2009) [69]; France

Patients with neck pain from a rehabilitation department

54.7 (14.2)

23 (56%)

Schneider (2013) [70]; Canada

Patients with persistent neck pain, referred to a tertiary interventional pain management centre

46 (NA)

37 (66%)

Sebastian (2015) [71]; USA

Patients with a diagnosis of neck pain

Range 30-75y

NA

Shahidi (2012) [72]; USA

Participants with neck pain recruited from a university medical campus and surrounding community

34.9 (9.9)

9 (47%)

Stenneberg (2018) [73]; Netherlands

Patients with neck pain recruited from five primary care physical therapy practices

45.2 (15.3)

19 (73%)

Sterling (2002) [74]; Australia

Patients with chronic neck pain of traumatic or non-traumatic origin, recruited via written advertisement within a university

31.63 (11.5)

13 (68%)

Uddin (2013) [75]; Canada

Patients with mechanical neck disorder

45.43 (11.88)^b

81%^b

Vernon (1992) [76]; Canada

Subjects presenting to the problem case clinic of a chiropractic college teaching clinic (mechanical neck pain syndrome, whiplash-type cervical strain injury)

37.5 (8.6)

12 (50%)

Werner (2018) [77]; Switzerland

Subjects with neck pain (non-specific or WAD) attending the physiotherapy department of a hospital

40.1 (12.35)

13 (65%)

Williams (2012) [78]; United Kingdom

Patients following a whiplash injury, attending an Emergency Department

41 (14.8)

13 (68%)

Williams (2012) [78]; United Kingdom

Patients following a whiplash injury, attending an Emergency Department

38 (11.3)

19 (50%)

Ylinen (2004) [79]; Finland

Women with nonspecific chronic neck pain, recruited through local occupational health care services

44 (6)

21 (100%)

Youdas (1991) [80]; USA

Patients referred to a Clinic Department of Physical Medicine and Rehabilitation with orthopaedic disorders

59.1 (15.7)

39 (65%)