Intervertebral disk of fourth lumbar vertebra

Looks like

The pad between L4 and L5: a large, thick disc, taller at the front, giving the lower back its inward curve. A tough fibre ring surrounds a soft gel core.

What it does

Joins the two vertebrae, absorbs shock and lets this level bend and twist a little.

Keeping it well

One of the two commonest levels for a slipped disc (sciatica): the L5 nerve is pinched, giving pain in the outer shin and top of the foot to the big toe. Numb groin or bladder trouble is an emergency.

Related conditions

• Axial spondyloarthritis
• Bone metastases and spinal cord compression
• Gout
• Haemophilia & bleeding disorders
• Lyme disease
• Marfan syndrome & connective tissue disorders
• Osteoarthritis
• Psoriatic arthritis
• Rheumatic fever & rheumatic heart disease
• Rheumatoid arthritis
• Scoliosis
• Spina bifida & neural tube defects
• Spinal cord injury
• Systemic lupus erythematosus
• Temporomandibular joint disorder