AKA (above the knee amputation): In general usage, this would be read to mean "also known as." For example, William Jefferson (aka "Bill") Clinton. However, in medical parlance, AKA means "above the knee amputation." A nurse scrubbing for an AKA is getting ready to assist in an above-knee amputation.
AKA is as opposed to BKA, a below-the-knee amputation.