The most common cause of weakness and pain associated with the spine is intervertebral disc trauma or disease. The unfortunate thing about our choice to build this site in a question and answer format is that the most common diagnoses are often not covered as extensively they should be - because there is less question about the problems at the vet's and because people tend to understand them a little better.

The spine is composed of a long series of bones connected through a series of ligaments with a shock absorber - the disc - between each connection. If support was the only job of the spine there would be a lot less pain associated with injuries to the disc area, probably. But the spine serves as a conduit for the spinal cord, too. This very large bundle of nerves runs through the centre of the spine and the individual strands of the bundle exit between the vertebrae at whatever level is necessary to do their job. The nerves pass between the outer edges of the disc and the bony protrusion of the spine. As long as everything is in its place this arrangement works fine. When the disc bulges or is damaged and calcifies it can put pressure on the exiting nerves leading to visible clinical signs of dysfunction in the area served by those nerves. By carefully considering where weaknesses and pain are exhibited it is possible to tell which discs are likely to be damaged.

If the disc is just putting a little pressure on the nerve there may only be pain. If the disc is damaging the nerve more significantly then weakness or paralysis will occur. In the case of pain alone it limiting exercise and utilizing a non-steroidal anti-inflammatory medication may be all that is necessary. If there is weakness then corticosteroids or even surgery may be necessary to alleviate the problem.

In a dog with pain and weakness in one or both rear legs there is a strong likelihood of an intervertebral disc problem. Other possible causes of problems do include the ones you listed from searching our site as well as localized injuries that sometimes mimic disc problems. When both cruciate ligaments in the knees rupture at the same time the resulting disability can strongly resemble the weakness and disability associated with disc injury. It may be possible that luxation of both patellae at the same time could also produce similar signs.