Hi Noeleen
Thank you for your question.
As you have correctly described you have degenerative
spinal stenosis. What this means is
arthritis in your back has led to growth of back tissues (yellow ligament) which in addition to bulging discs narrow the
spinal canal and pinch the nerves going to legs. This is the cause of
sciatica.
As a part of treatment the medication which is more helpful for this nerve type of pain is
gabapentin or
neurontin. However it needs to be taken under supervision of a doctor as it needs monitoring for side effects. Next option if the medications don't work is trying epidural steroid injection/s which are done under image guidance and many times are useful for pain relief though they do not 'cure' the spinal stenosis as such.
Regarding your question about returning to gym, I am glad to hear that you are reasonably fit. I would advise strictly avoiding bending, twisting and lifting weights kind of exercises. Walking is a good exercise for you. Working on the treadmill is fine as far as you keep the speeds low and make it fast walking and rather than running. If this gives you
back pain or aggravates your sciatica please refrain from these activities. If you can tolerate the treadmill from pain point of view, it is unlikely to cause any acute worsening of arthritis and stenosis changes in your spine.
Hope this is useful and please let me know if I can be of further assistance.