Patellofemoral problems are the most common causes of reoperation following total knee arthroplasty. Complications include wear, loosening, stress fracture, and patellar instability. Of these, patellar instability may be the most frequent problem and can be difficult to treat. Multiple factors contribute to maltracking of the patella, including residual valgus limb alignment, patella alta, prosthetic design geometry, excessive valgus placement of the femoral component, malrotation of the femoral and tibial component, quadriceps contracture, capsular dehiscence, dynamic instability, failure to perform a lateral release, excessive patellar thickness, and asymmetric patellar bone preparation. Proper treatment involves determining the mechanism for instability to help choose the best surgical solution to the problem.