There are actually three different ways to have surgery done to replace both knee joints. The operation is called a bilateral total knee arthroplasty (TKA). A single hospital stay with both knees replaced four to seven days apart is a staggered TKA.
Having both knees done during a single operation is called a sequential TKA. The third choice is the staged TKA. In this operation the patient has one knee replaced at a time separated by weeks to months. Two separate hospitalizations are needed.
There are pros and cons to each type of surgery. If the patient is healthy the staggered or sequential methods are possible. There is the chance of greater blood loss and transfusions required with either of these methods.
Patients with more serious health problems may have to use the staged operations instead. On the other hand the staged group seem to need less rehab. Having the first knee replaced helps them prepare for what to expect when the second one is done later.