Physio Bobby Bacic told the Lions' official website: "The surgery took just under two hours because he at first trimmed some of Danny's cartilage and then repositioned his knee cap.
"He re-attached it using a graft that the surgeon had harvested from one of Danny's hamstrings.
"Danny will now begin the challenge of doing his rehab and we'd expect this to take up to nine months due to the severity of the original injury."