Do they ever do those slippery injections for the spine? I had three on my knee and they worked like a charm. I've got arthritis in my back and thought maybe the same treatment might help.
You may be referring to hyaluronic acid (HA) injections. This is indeed, a form of slippery injection. The HA is the goo that lubricates the joint. It's a natural part of the synovial fluid found in a normal joint.

The procedure itself is called viscosupplementation. That's because HA increases the viscosity of the synovial fluid. Viscosity refers to how slippery the fluid is inside the joint.

Viscosupplementation works well for some patients with knee osteoarthritis (OA). It has been tried with the shoulder, hip, hand, and foot and ankle. More recently, results from a small study (13 patients) using HA in the facet joints of the spine has been reported.

No changes in pain or disability were observed after one injection. Follow-up was only six weeks. The authors pointed out that one injection might not be enough to really gauge the results of viscosupplementation for the lumbar spine.

And the optimal dose isn't known either. Since the spinal joint is much smaller than the knee, the amount of fluid used in the injection had to be decreased. But perhaps they didn't use the right amount of HA. More study is needed before this treatment is adopted for spine OA.