The objective of this study is to examine the short and long-term effect of myofascial trigger point injections with either a local anesthetic or saline in patients with chronic low back pain presenting with myofasical pain syndrome.

Inclusion Criteria:

• CLBP of non-malignant origin, with or without accompanying leg pain, including patients with history of previous back surgery or trauma
• MPS as evident by at least one active MTP, located medial or lateral to the posterior iliac crest involving the gluteus maximus or medius, quadratus lumborum and erector spinae muscles
• While not precluding the participation in the study, MTP in other areas will not make patients eligible
• Pain lasting for at least six months

Exclusion Criteria:

• Any current motor weakness, but not sensory loss or abnormal reflexes in the lower limbs
• Any injection or nerve block in the low back in the last 6 months
• Local or systemic infection
• Bleeding disorder or the use of anticoagulation medications
• Known allergy to local anesthetics
• Poor understanding of written and spoken English or French