The key thing is to use common sense. You should also keep your weight down because every pound you gain adds three pounds to the force to the knee. The design of the implant. Small abrasion particles from the implant may play a role in implant loosening. Some designs shed more particles than others.
Wound healing can occasionally be a problem after knee replacement.
The skin wound over the knee sometimes does not heal completely. Parts of the skin may die after the surgery. This is a major complication which occurs very rarely. Every precaution is taken to prevent it. Fat legs are more prone to this complication.