After my disc injury from a few years back, I have to make sure I train effectively and choose my battles carefully to ensure I don't regress or relapse.
Due to the nerve damage, my left leg was compromised, so I consistently try to not overload my spine and use as many opportunities as possible to work my legs individually. I love playing with the BOSU for elements of my training and that includes simple balance/coordination/proprioception at times. .
An unstable surface increases activation of the abdominal area and allows for slightly more oomph per exercise when compared to a stable surface in many cases. One legged squats hit my quads/glutes/hamstrings as well as ensuring the leg lift engages my abductors. Give it a try on land or on BOSU.