Hello,
The tag Reverse Jointed Legs is a small tag with only 15 posts and no wiki, I propose a wiki definition that only allows the tag to be used on mechanised entities such as robots, walkers and mechas, removing the tag from existing biological entity posts with it. I'd like to hear inputs from other users too on this topic.
TL;DR: A proposal for the phrase 'Reverse Jointed Legs' to be used for describing mecha/walkers with birds-like reversed jointed legs, bird may look like they have reversed joints but they are anatomically similar in posture to a mammalian hind leg, you wouldn't tag a cat with reverse jointed legs, and going back to mass tag every post that have birds/bird_legs with it isn't entirely applicable either. It is a term coined for and should be used exclusively for mechanical creations.
My argument for this is based on the concept of mechanical 'reverse jointed legs' is inspired by the appearance of avian legs, but there are no true reverse joints in nature for endoskeletal vertebrates, the appearance of a reverse jointed knee is purely visual, anatomically speaking these reverse jointed legs has the exact same amount of joints and equivalent parts as forward bending legs such as human's. Where as mechanical constructs can be inspired by biological anatomy while not being bound by the amount of joints, and some of them are capable of having a true reverse joint.
The most notable biological example being the flightless birds that relies on their legs for movement, digitigrade (creatures that walks on their toes) such as chicken and ostrich appear to have a backward bending knee, but when anatomically compared to a human, that 'knee' is actually an equivalent of an ankle, and below it is their tarsal/metatarsal (our equivalent would be the palm of foot). In the case of an ostrich, their femur (thigh) is actually inside of their body and provides torsional movements. Some water birds such as ducks may have their femur further inside their body, in the extreme case of a penguin their tarsal is far smaller, giving them the appearance of having stubby legs, but anatomically speaking they still have all the parts and joints present.
'Reverse jointed legs' does not apply only to avian, in fact most if not all digitigrade animals have this kind of leg structure, most easily recalled example being cat and dog hind legs. Unlike birds, their femur is not inside their body, as well as having different length of each individual leg sections, it does not give off the 'chicken leg' appearance but still performing a similar load bearing posture like the avian legs, simply because they are both digitigrade creatures. By standing on your toes we can also assume the 'reverse jointed' stance, but within minutes we will quickly realise our body is not fit for such a posture and our weight distribution places stress on body parts that we don't typically place load on, we as plantigrade (walks on our soles) are not using our phalanges/tarsal joint, the appearance of our forward bending joint is because anatomically our leg parts are designed to have an upright load bearing femur.
Star Wars' AT-ST walker is widely regarded as a reverse jointed walker, even though upon closer examination one can see that they do indeed have a load bearing femur, it's just very short and albeit not entirely visible, as well as not capable of torsional movement, an AT-ST walker just have a very high 'knee'. Even though it isn't a true reverse joint because it mimicked an avian leg down to every joint, the term was applied because it has the appearance.
There are examples of true 'reverse joints', a more recent example being Bethesda's Starfield, the NPC robot companion 'VASCO' has only two sections on their leg connected by a backwards knee, the waist joint is a true backward bending load bearing joint, anatomically different from vertebrates by having less joints/sections. Another example is Boston Dynamics' robotic product 'Spot', having backwards knee connected two section legs, also having the backwards bending connection joint at the torso, not having digits what so ever.
Thank you for your time.