I've heard that a herniated disc can repair itself. Is this true?
Spontaneous reduction of disc herniation is possible. It's even been reported in up to 95 percent of patients in one long-term study in Japan. Most likely what happens is a process called degenerative disc disease.
As we age, the water and protein content of the body's cartilage is less. This change results in weaker, more fragile and thin cartilage. The same thing happens to the discs between the vertebrae.
Narrowing of the disc space called spondylosis occurs with degenerative disc disease. It can be seen on x-ray tests or MRI scanning of the spine. Loss of disc height and spine flexibility often occurs. There may or may not be symptoms of back and/or leg pain.
If neurologic symptoms are severe (numbness, tingling, weakness) then surgery may be needed to prevent permanent nerve damage. In such cases the body isn't given the chance to heal itself through spontaneous reduction. Immediate surgery may be needed.
Tetsuo Masui, MD, et al. Natural History of Patients with Lumbar Disc Herniation Observed By Magnetic Resonance Imaging for Minimum 7 Years. In Journal of Spinal Disorders. April 2005. Vol. 18. No. 2. Pp. 121-126.