Dr. Robert Bray, Grey's neurologic spine surgeon and medical director of the DISC Sports and Spine Center in Marina Del Rey, Calif., said he would perform a microdiscectomy on the 50-year-old actress later this week. The surgery involves removing a very large disc fragment that broke off, and then repairing the hole in the disc.
"The disc fragment is about 17 millimeters, which is very large," said Bray. "It won't get better and will get progressively worse. She's starting to feel some weakness, so it's the only option."
Grey ruptured her disc the night before her final dance with partner Derek Hough and was briefly hospitalized.
"I did not think I was going to be able to dance," Grey told "Good Morning America" after the show's finale.
The injury was yet another painful event in a year that had already taken its physical toll on the actress. Bray said she had four neck surgeries this year. One of these surgeries involved inserting a plate in her neck, while she had other surgeries to remove a cancerous thyroid. Grey suffered a severe neck injury after a serious car accident in 1987, and has suffered from chronic pain ever since.
"Her head was falling off forward. She had a 30-degree angulation of her neck," said Bray.
Bray said the night before the final round of dancing, Grey ruptured a disc in her lower back.
"She called me in the morning on the day of the finals and was in tears. She was in terrible pain," said Bray.
Grey received epidural steroid injections, which helped alleviate the pain, and she was able to walk. Bray said she desperately wanted to dance, but he wanted her to be very cautious.
Bray examined her before and after each dance. Her legs were strong, she was in no pain, and the dances were very short, so he was confident she was in no danger of doing any further damage.
"If it's not going to harm you, people are better off moving around than sitting around," said Bray.
A ruptured or herniated disc happens when the spongy discs in between the vertebrae of the spine rupture and the contents of the disc leak out, causing the disc to bulk or break into pieces. They can be painful, but many people suffer no symptoms at all and don't even know they are injured.
"If the ruptured disc is in the neck area, the pain starts in the neck and runs down the arm," said Dr. Scott Boden, professor of orthopedic surgery and director of the Emory Orthopaedics & Spine Center in Atlanta.. "If it's in the lower back, then there's pain in the low back that runs down one of the legs."
Since the ruptured disc is in Grey's lower back, medical experts say there's little chance of physical activity causing serious injury, such as a spinal cord injury. If the disc were in her neck, the chance of a spinal cord injury would be greater, but still unlikely. The rupture would have to be severe enough to cause a great deal of compression that would damage the spinal cord.
In most cases, rigorous physical activity just makes pain worse.
"If it's a really herniated disk causing pain shooting down arm, then engaging in physical activity runs the risk of continuing to aggravate pain. You're not giving it a chance to get better," said Boden.
While herniated discs can happen to anyone, risk tends to increase with age.