Table 1.

Characteristics of included studies

Study	Review	Sample size (n)	Groups	Follow-up (weeks)
Atkinson [38]	Pharmacological	83	4	12
Barendse [27]	Injection	28	2	8
Brinkhaus [52]	Complementary	298	3	8
Chrubasik [32]	Complementary	210	3	4
Chrubasik [33]	Complementary	88	2	6
Coats [39]	Pharmacological	293	2	4
Foster [25]	Injection	31	2	3, 8
Freeman [30]	Injection	57	2	26
Frerick [31]	Complementary	319	2	3
Geurts [29]	Injection	80	2	13
Haake [19]	Complementary	1,161	3	26
Katz [40]	Pharmacological	118	2	12
Keitel [34]	Complementary	150	2	3
Leeuw [18]	Non-medical	73	2	26
Manchikanti [35]	Injection	120	2	13, 26, 52
Manchikanti [36]	Injection	75	3	13, 26, 52
Mendelson [41]	Complementary	154	2	18
Pauza [42]	Injection	56	2	26
Peloso [44]	Pharmacological	336	2	13
Ruoff [43]	Pharmacological	318	2	13
Sherman [20]	Non-medical	96	3	12
Smeets [24]	Non-medical	212	3	52
Soriano [37]	Non-medical	71	2	2
van der Roer [21]	Non-medical	102	2	52
van Kleef [26]	Injection	31	2	8
van Wijk [28]	Injection	81	2	13
Witt [22]	Complementary	2,623	2	13
Yelland [23]	Non-medical	88	4	52