Pathomechanics of the femoropatellar joint following total knee arthroplasty.

Persistent discomfort in the femoropatellar joint is still one of the most disappointing aspects following total knee arthroplasty (TKA). Especially, TKA without patellofemoral replacement has a significant incidence of patellofemoral problems with a frequency between 5% and 45%. Pathomechanical factors in the development of retropatellar problems are loss of patellar thickness and retropatellar erosions. In 157 TKAs using Gschwend, Scheier, Bähler (GSB) joints without patellar resurfacing, pathomechanically postoperative vertical patellar malposition appeared to be the main cause of dysfunction. In many cases, the implantation technique leads to an artificial form of patella alta. This altered knee anatomy results in pathologic biomechanics, thus leading to reduced function. The combination of altered anatomy and reduced function leads to extensive patellar destruction and ultimately to intractable retropatellar pain.