Im on the fence on this one. I see both sides. I just hope we can come to a conclusion and make them in a unified rules that everyone will follow.
It can cause damage but at the same time so can any # of things, this is MMA. But it is not solely to fuck someone's knee up. It can be used to hinder their movement, just like a leg kick. or to keep them at a distance.
It seems like one of those things that you like to land on your opponent, but hate when they land it on you. Thats how I feel. I wouldnt be upset either way, it just needs to be addressed and followed.
banning spinning elbows would be a joke. Obviously if it lands on the back of the head, then yes its illigal.
Id like to see 12-6 elbows made legal and possibly kicks, knees to the head of the grounded opponent.
eyepokes are another issue. They are clearly dirty and dont belong in MMA. but there are a lot of legitimate techniques that require you to keep your arm extended in your opponents face. You can block their vision and look to land, play with their defence, etc.
Even with a worse case scenario, which we really havent come across at the moment. If someone's knee was flat out blown out from a kick to the knee. You could still do the same amount of damage to a major joint from an armbar or kimura. Look at how many armbars have damaged fighters over the years... Look at Nog's arm after the Mir fight, that will never be the same.