The midfielder left the field on a stretcher after coming on as a second-half substitute during Wednesday night's 1-0 defeat to Hibernian.
He was expected to spend the night in Perth Royal Infirmary following the SPL clash at McDiarmid Park.
The club has now confirmed initial fears of a leg break.
They wrote on Twitter: "Confirmed that @davidrobbo12 broke his leg in last nights game and is to undergo surgery today."
- Sports & Recreation