What is the recommended treatment for scoliosis if I am 21?

Size of the curve. Routine follow up until curve is proven nonprogressive.45 degrees surgery maybe needed to prevent progressive deformity.
It depends... There are multiple types of scoliosis. The most common type in 21 year old patients is adolescent idiopathic scoliosis that was treated without surgery. The answer to your question depends on the severity of the curve. Most curve 40 degrees can be treated without surgery. Curves that show rapid progression or severe rotation may require surgery.