extensor mechanism failures post knee replacement

Causes of extensor apparutus dysfunction 

Patellar  fractures

quadriceps tendon rupture

patellar tendon rupture

patellar button loosening

Patellar  fracture

Conservative is  the main stay unless displaced  fracture or loose button

Complications of internal fixation is high

if the fracture and implant is stable - conservative

 if fracture is stable implant unstable. remove loose implant

 if fracture is unstable and implant unstable

 consider conservative first 

 Remove implant and fix

 or Recently  bypass  patella with  neoligamant and remove the implant if patella is unfixable