The lives of some elderly people are rendered miserable by progressive bow-leg deformity brought on by arthritic destruction of both knee joints.
Total knee replacement offers a chance for a return to a near normal life, but can be demanding on the surgeon when the condition has been allowed to progress to extremes.
A total knee replacement would offer her almost complete correction of her disability, but the arthritis had been left until there was insufficient quality bone to hold the prosthesis (metal/plastic implant).
Also both knees would need to be done at the same time - otherwise the operated leg would be longer than the other, making her life even more difficult.
Balancing was critical in this case, as one had to ensure an accurate cut of the tibia and then referencing off from the tibia before cutting the femur. This was to ensure that sufficient external rotation of the femur was done.
The patellae would also need to be resurfaced.