Table 1 Inclusion and exclusion criteria

Participants were required to have a new LBP episode within the previous 3 months.

Chronic LBP (>  3 months duration)

At least 18 years of age

Previous chiropractic, medical, or physical therapy treatment for the current LBP episode

Speak/understand English

Radicular features including leg pain distal to the knee, numbness/weakness of the lower leg, or positive nerve root tension/neurological signs

Minimum levels of self-reported pain (3 on 0–10 scale)

Current use of prescription pain medications

Minimum levels of self-reported disability (20 on 0–100 scale)

Contraindications to spinal manipulation, including:

• Previous history of metastatic cancer

• Severe osteoporosis

• Fracture or instability

• Prolonged anticoagulant or oral steroid use

Agree to be randomized

Agree to attend 2 office visits per week for 4 weeks

Agree to cooperate with follow-up data collection

Agree to have blood drawn