What Causes Sudden Sharp Pain In The Calf Muscle, Ankle And Foot?

Question : I'm 64 and in good health. A little overweight but a terrible hypochondriac - have been my whole life. About 30 years ago I threw my back out after heavy lifting, and it periodically has gone out ever since. When it does, it generates severe pain primarily in the lower left of my back, about waist high. Sometimes I'm actually crooked. I'm able to control it by wearing a brace after it goes out, which relieves the pain. It usually happens when I stand up and turn (getting out of a car, off the toilet, etc.).
For the last several months my back has been sensitive, and sometimes very painful when I stand up and turn. This has been my pattern for years. The back brace will get me back in sync, but the back remains fragile. In addition, over the last 6 months or so I've noticed a very mild pulling feeling (comes and goes) sometimes in my lower left calf, sometimes around my left ankle. Not really bothersome but slightly noticeable because I'm such a hypochondriac. It comes and goes, but when it happens it occurs when I'm walking - almost a "weak" feeling but absolutely NO loss of strength in my leg. Also, for a week or so I've noticed, (only when I'm lying down on my back at night), a few very mild one second spasm in my left foot - only seems to take place when I'm lying on my back but I might feel it 5 or 10 times a night.
I don't have sciatic pain going down my leg but do feel some occasional discomfort in my left buttock.
I have no other symptoms - no unusual headaches, can walk heel to toe forward and back, no balance problems, facial symmetry, normal vision, both eyes are coordinated when looking up, down, peripherally, normal finger to nose test, no problem standing with eyes closed, etc.

Here's my question.......I'm thinking the calf, ankle, foot sensations are back related....do you think I can rule out more serious concerns like MS, ALS, brain tumor?

Thanks very much.