What was done
A meta-analysis of ten randomised trials. Compared with usual care or education, yoga showed strong evidence of reducing pain and disability in the short term, and moderate evidence of reducing pain over the longer term.
What it does not show
No evidence of change in overall quality of life, and a 2021 update of the same question rated the trials as low to moderate quality. Good for a stiff back. Not evidence of anything beyond that.
Cramer, Lauche, Haller and Dobos (2013). A systematic review and meta-analysis of yoga for low back pain. Clinical Journal of Pain.