A couple of years ago I had some tendinitis in my left hand. It was not too serious, but it took me out of action for about a week. When I got hurt among the things I was working on were a bunch of Rachmaninoff etude-tableaux, a Prokofiev concerto, a Dvorak quartet and some Liszt and Scriabin etudes; a lot of technically demanding music. I combed through Wilde Jagd, the cadenzas from the concerto and Rach's op. 39, n. 9 looking for anything stupid in my technique. Which of those caused my injury? Any of those pieces could have been the culprit but, ironically enough, I got tendinitis from Schubert's Musical Moment number 3, in F minor (the famous one that everybody plays as much as Für Elise).
The left hand plays staccato the whole time, jumping constantly (not big leaps though, but just enough so that they can't all be played in a single position). Instead of simply keeping my hand in a relaxed position and moving it for each jump (actually leaping), I was spreading out my fingers as far as I could--- as if that would actually help me bring the notes together--- trying to span the whole chords and not releasing the tension at all.
Watch out for that, it's one of the more common injury causing problems out there. I write this because, today, I had another teacher's student come up to me to ask about a pain she had. Her left wrist was swollen, her muscles (near the elbow) sensitive to any movement and she had a general pain that came all the way from her shoulder. She could barely move her hand anymore, much less play--- I figure she won't be playing for at least a week, probably two. She was playing Moszkowski's fifth etude and kept her left hand spread out the whole time while she played while the pain just got worse and worse. Her teacher actually told her that she got hurt because of the sudden cold weather we've been having, and made her play the etude at an exam (which just made the injury worse).
Constant leaps in the left hand--- from a single base note to an upper chord, for example--- are one of the most common pianistic patterns out there. It is in everything from Beethoven to ragtime. Make sure you are actually making the jumps with your hand in a comfortable position at all times. Don't force your hand into an open position, trying to span the whole jump all the time. That is one of the quickest ways to get hurt.