Patients with prior patellectomy may continue to experience pain and instability following total knee arthroplasty. Seventeen such cases were found, 14 of which were available for study. One knee was fused for deep infection. Of the remaining 13, six were revised for continuing pain. The final results correlated to the intrinsic stability of the prosthesis. All hinges (5 cases) had good results, one of two unlinked hinges had good results, and two of six semiconstrained prostheses had acceptable results. Since the patellar mechanism with the cruciates functions as a four-bar linkage to ensure functional anteroposterior stability, one of these linkage systems must remain intact. If both are destroyed, a prosthesis with inherent anteroposterior stability should be used.