Aha. Found this:

The Warg scene that includes the infamous shot of Legolas leaping onto the horse, was filmed on the same day that Orlando fell off his horse and cracked his rib. He landed on a rock and Gimli's scale double (Brett) fell on top of him. So they couldn't film Orlando actually jumping onto his saddle, because of the injury. Later in post production, about six months before the release of TTT, Orlando had grown a beard, for the filming of Ned Kelly. He wasn't permitted to shave, which meant he couldn't do the pickups for this scene in TTT, so they created a CG Legolas to do the actual springing onto the horse.

[link]

That's right, I remember now. I was conflating the two injuries in my head.

Clearly this means I need to revisit the trilogy.... the things I do in the name of history...

Ok. So why then did they CGI it in so awkwardly?

I always thought it's cause pixel!Legolas is mounting the horse with the wrong hand. A real person doing that would probably break something in his arm.

The way they did it, it looks like he should have his whole damn arm ripped off.

I assuming time/budget/talent constraints--it's not the only time Leggy looks off.

Yeah, the run up the oliphant looks off, but not as bad, to me anyway. The horse thing is the only thing that takes me out of the movie.

[link]

For a refresher.

And in other TTT comments - we watched the extended version and Jeebus Christie is it looooooong. I fast forarded through all of the annoying hobbit stuff.

If they had just had him take a moment to switch bow hands, it would have been flawless. I have to just not watch that every time.

inevitable movie-throwing x-post

And in other TTT comments - we watched the extended version and Jeebus Christie is it looooooong. I fast forarded through all of the annoying hobbit stuff.

Dude, I watched the extended marathon in the theatres leading up to TRotK. 12 1/2 hours in the theatre--all while I was six months pregnant and after drinking a large soda.

Cashmere = insane.