Injury Tip Sheet: HNP

Bryan Christie

Bryan Christie

Injury Tip Sheet: HNP
(Herniated Nucleus Pulposis)

Learn what you need to know to help treat and prevent this common back injury

Kathy Weber, M.D., M.S.
Daphne R. Scott, PT, Dsc
Chicago, IL

Fast facts

  • HNP’s occur in the lumbar region (lower back) 80% of the time
  • Also known as a herniated or slipped disc
  • Common cause of back pain
  • Only 10% of herniated discs require surgery

What you need to know

What is HNP?

  • Intervertebral discs are located in between vertebrae in the spinal column.  They are designed to provide cushioning for the vertebrae and to increase the spine’s capacity to bear weight
  • Each intervertebral disc is made up of an inner and outer layer; the annulus fibrosis is the outer layer and the nucleus pulposis is the inner layer
  • The nucleus pulposis is a spherical, gelatinous mass located inside the annulus fibrosis
  • A HNP occurs when the nucleus pulposis is forced beyond the annulus fibrosis into the spinal column.  This can exert pressure on nearby nerves or the spinal column causing pain, numbness, weakness, and muscle atrophy if left untreated

Signs & symptoms

  • Pain in the back, typically in the region of the injured disc, that can continue down along the buttocks and leg and into the foot
  • Numbness, tingling, or weakness, referred to as sciatica, that feels like electric shock waves extending down the leg
  • Muscle spasms or twitches when in certain positions or when laughing or coughing

When should I see a doctor or other professional?

  • You should see a doctor if the pain or sciatica is keeping you from walking or performing your daily activities
  • If you experience weakness, a change in your normal bowel or bladder function, increasing pain or numbness
  • Your physician will perform a neurological exam to determine the cause of your pain


  • HNP’s can occur from single sudden trauma, such as an extreme lifting and twisting motion
  • Intervertebral discs begin to degenerate when a person is about 25 years old at which point discs can begin to develop weaknesses, making them prone to injury

Risk factors

  • If there are any weaknesses in the outer layer of the disc, the nucleus pulposis is more likely to extend outwards under extreme pressure
  • People over 50 are more susceptible to disc injuries
  • Athletes may be at greater risk if they participate in a sport that requires sudden or excessive twisting and bending activities.
  • Men are more susceptible to HNP’s than women
  • Poor daily postural habits and poor lifting mechanics
  • Obesity and deconditioning

What you can do


  • The key to preventing back injuries is to build stability in the core region
  • Control your weight with diet and proper exercise
  • Ensure that when you perform heavy lifting you use proper technique

Recommendations for treatment and rehab

  • Typical treatment involves rest, anti-inflammatories (if appropriate), and physical therapy exercises to return the muscles in the back to their normal activity
  • Other treatments may include: muscle relaxants, narcotics, and steroid injections
  • If the individual does not improve with a comprehensive conservative treatment program or if there is refractory pain or a neurological deficit (i.e. weakness, bowel and bladder dysfunction) then surgery is recommended.
  • Most individuals do not require surgery

What can I do to stay active?

  • Participate in activities that do not reproduce or increase pain
  • Avoid prolonged sitting as this tends to increase pressure on the disc and increases symptoms
  • Activities such as walking, swimming, or elliptical trainer may be tolerated.  These activities keep the spine in a straight or upright position and are better tolerated when an individual has a herniated disc
  • Avoid cycling since it requires the spine to be in a flexed position placing more stress onto the disc
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