To delineate the underlying mechanisms that contribute to chronic low back pain, by extending our knowledge on structural characteristics of the lumbar multifidus muscle using ultrasound muscle imaging, and by examining the association of structural features with functional performance, more precisely proprioceptive control.

Inclusion criteria for chronic low back pain group:

• Non-specific low back pain, during 3 or more months, without radicular leg pain
• Modified Low Back Pain Disability Questionnaire > 20%
• Indication for MRI of the lumbar spine
• No contra-indications for MRI
• Informed consent to participate

Inclusion criteria for healthy control group:

• No history of low back pain needing medical treatment or resulting in limited activity level
• Any low back pain in the previous 3 months
• Informed consent to participate

Exclusion criteria for all subjects:

• Pregnancy
• Previous trauma or surgery to spine, abdomen or pelvis
• Structural deformity (e.g. scoliosis)
• Neurological/neuromuscular/systemic disease
• Inability to lie prone for 20 minutes

Leuven and surroudings