Nucleus pulposus L5-S1

Looks like

The soft, gel-like core of the disc between L5 and S1 in the lower back, sitting slightly behind the disc's centre inside a ring of tough fibres.

What it does

Mostly water held in a gel; it spreads load evenly across the vertebrae and acts as the pivot on which this level bends.

Keeping it well

One of the two commonest levels for a slipped disc (sciatica): the S1 nerve is pinched, giving pain in the calf, sole and outer edge of the foot. Numb groin or bladder trouble is an emergency.

Related conditions

• Axial spondyloarthritis
• Bone metastases and spinal cord compression
• Cauda equina syndrome
• Gout
• Haemophilia & bleeding disorders
• Herniated disc
• Lyme disease
• Marfan syndrome & connective tissue disorders
• Neck pain and cervical spondylosis
• Non-specific low back pain
• Osteoarthritis
• Psoriatic arthritis
• Rheumatic fever & rheumatic heart disease
• Rheumatoid arthritis
• Sciatica
• Scoliosis
• Spina bifida & neural tube defects
• Spinal cord injury
• Systemic lupus erythematosus
• Temporomandibular joint disorder