total knee replacement

For an operation -- specifically, total knee replacement -- how do we identify when the "Goldilocks moment" arrives? That is, not too early, when there's little benefit to the patient bearing unnecessary risk. Or not too late, when the delay has further limited physical activity, increasing long-term disability and recovery. A new study searches for some answers about how to find the "just right" time. 
A relatively small study--50 patients undergoing total knee replacement surgery vs. 50 controls getting PT alone--showed a significant benefit for the surgery. But complications occurred with surgery. Some of the nonsurgical patients elected surgery later. While not definitive, surgery works well for most with knee OA.