Do bees have knees and, if so, what's so special about them?

Bees, like all insects, have six sections to their legs: the coxa, trochanter, femur, tibia, metatarsus and tarsus. Each is connected by a joint and the one most like a knee is between the femur and tibia. Bees have lots of other specialised structures on their legs to carry pollen, but the knee itself is no more remarkable than any of the other leg joints. Probably the most special thing about them is that they rhyme with bees. The phrase seems to have evolved in 1920s America, along with 'the cat's pyjamas'. Other seemingly arbitrary terms of distinction from that era that have since died out include 'the snake's hips', 'the kipper's knickers' and 'the sardine's whiskers'. Of all of these, the only one actually found in nature is the bee's knees, so perhaps that's what's so special.