Chancy had LS. I can't say how early it started being apparent, because I adopted her as a bounce at 10 years old, and she already had clear symptoms: scuffing of back feet when she walked, rear leg weakness, inability to support weight if one back leg is lifted, sinking of rear end when hands were run even gently along her lower spine, slightly awkward stance as if she was not quite aware of where her back feet were...
I started her right away on Glucosamine and fish oil, and it helped quite a bit. Later I added MSM. Can't say if that helped much as that was near the end.
As a standard practice I give all my pups fish oil and glucosamine. I think Tipper is just starting to show very slight signs of LS.
For Chancy, my vet suggested regular light exercise. Brisk daily walks are perfect. Especially on slightly uneven ground (grass/snow instead of pavement) as it helped focus her on where she was putting her feet. All-out running was not recommended, as a spinal injury could be more likely, since the nerves weren't firing quite correctly.
Also, when Chancy had flare-ups of back pain (as evidenced by yelping when she'd try to lay down or stand up, restlessness and inability to get comfortable) she received acupuncture treatments and pain meds. Usually the flare-ups receded within a couple of days. I tried six months of chiropractic treatments for her, but I felt that didn't help her at all.
Interestingly, I've read that Laryngeal Paralysis is not an uncommon "companion ailment" to Lumbosacral Stenosis. Chancy had both, which supports that theory.