Primary outcome – subgroups. Best efficacy for optimal dose and administration of each intervention within 4 weeks after treatment start. Mean difference over placebo for pain measured on a 100 mm visual analogue scale (VAS) is shown as columns, and error bars indicate 95% confidence limits. The horizontal dotted lines indicate subjective thresholds for mean perceptible improvement (lowest), mean slight improvement (middle) and mean important improvement (top). Abbreviations: LLLT (Low Level Laser Therapy), TENS/IF (Transcutaneous Electrical Nerve Stimulation and Interferential Currents), EA (Electro-acupuncture).