Yes, I have osteoarthritis (OA) in my lower back ....... Pelvic and Lumbar spine (Sorry, I probably spelled Lumbar wrong)

As well as haveing OA in the entire rest of my spine and neck.
Also in both knees and both feet.

I also developed osteoporosis in my spine and combined with the OA it has resulted in a 15% bend convexly to the left. That bend pulled the muscles too tight over my hip and resulted in reoccurring hip bursitis.

OA is a long story since it progresses over the course of many years.
So I'll try to just mention things about OA in the lower back.

But you asked what to expect?
I think you can expect it to get worse. (Sorry)

Since you are in the stage of OA in the lower back only, I'd like to say DON'T let your backache rule.
Do your very best to stand straight even if your back complains.
Don't let it develope into a permanent slump or slouch position.
One thing about the spine, once bent you cannot unbend it.
You can, however slow down the bending by keeping your skeleton as properly lined up as possible.

I recommend useing a knee contour pillow between your legs while you sleep each night to get rid of morning back ache (This simple idea works wonderfully after just a few nights). This keeps the skeleton properly lined up and results in less strain all night long on the muscles and nerves surrounding the spine. Mornings become a lot better.

A Physical Therapist can guide you in the proper excercises to help with OA in the lower back. These are very helpful. As a non-medical professional I also recommend stretching straight up reaching for the ceiling as much as possible.

Wheels are your friend.
Consider getting things like a wheeled grocery cart, wheeled yard carts, all the handy things on wheels so you can avoid lifting and carrying heavy objects. Non-impact excercise to maintain muscles is excellant, but picking up and carrying 20 pounds is not..so think about wheels.

I go to a chiropractor on a regular basis and he has worked wonders with my arthritic spine.