Why is recommending two knees that require toe loading contraindicated for a bilateral TF amputee?

Recommending two knees that require toe loading is contraindicated for a bilateral transfemoral (TF) amputee primarily because of the difficulty in sitting. In bilateral TF amputees, the knee joints play a crucial role in stabilizing the individual during various activities, including sitting.

Knees that depend on toe loading generally require that the user control the knee function by shifting their weight forward onto the toes. This design inherently makes it difficult for the user to flex the knee if they are sitting, as there is no forward weight shift occurring. This can hinder their ability to get into and out of a seated position comfortably, limiting their independence and quality of life.

In contrast, other options present challenges but do not encompass the critical issue of sitting as effectively. For instance, while locomotion and weight shifts could be impacted, they are not the immediate concern that arises from the traditional seating positions. The unique biomechanical requirements of bilateral TF amputees necessitate a knee design that allows for adequate control and flexibility for both movement and sitting.