When we talk about musician injuries or injuries in general, we tend to think overuse: playing too much or fundamental misalignment, which is sometimes (but not always!) the case. It can also be easy to blame oneself for such an injury, or to receive blame from teachers that your setup isn't good, that you didn't take breaks, or my personal favorite “you’re doing it wrong because if you did it right, it wouldn’t hurt.”
This is not always the case! In Elizabeth Andrews' book, "Muscle Management for Musicians," she outlines three different categories, which I've found helpful to look at and evaluate, both for students, teachers, and professionals.
1. Musician Versus Instrument: This can mean the size and shape of your particular instrument (one viola vs. another) or having to play a lot of contrabassoon/bass flute/subcontrabass sax/etc. in relation to your normal workload. This can also be as simple as pointing out that not everyone can play a full size bass or that moving between piccolo and alto flute can be tough on the hands. There are an infinite number of ways to alter one's setup to potentially help support the body, and those changes definitely fall into this category, but setup is usually not the only thing to blame.
2. Musician Versus Environment: This is a category orchestral players are certainly aware of- chairs, stand height, conditions of the room/space/concert hall, temperature, etc. This can also include clothing restrictions (violinists in tuxedos, high heels for performance, or simple elevating one foot to play bass or guitar) or even carrying one's instrument (s) upstairs, around the city, etc. Wielding a contrabassoon, bass, cello, harp, or tuba is not the easiest! For string players, this could also include the way one has to rotate one's chair or torso to share a stand, or the cramped sitting positions of the orchestral pit. This category also includes the acoustical aspects of the space- perhaps creating conditions that are excessively loud, resonant, or putting players too close together.
3. Musician Versus Self: In my mind this includes the other things we do that stress our arms, body, voice, spine, etc., which includes computer use, cell phone use, driving, standing (!), sleeping, etc. Sometimes we sleep on one side over another, we favor one hand for texting and computer use, or always use one hand to open doors and such. What are the other stressors in your life that may impact your body?
I love Elizabeth's categories, and although I've altered the descriptions a bit to be more relevant, I think they're great points. I would however, add a fourth category.
4. Musician Versus Music: Sometimes, even against your best intentions, the repertoire that you're studying, playing in ensemble, or preparing for an audition is too much for your body. I've previously talked about how Paganini may have been hypermobile- for some folks, the extensions and left hand demands of the caprices are too intense and not practical. This is true for a lot of contemporary repertoire in general- as our levels of mastery and virtuosity have skyrocketed, so have the demands of our pieces, often bringing near impossible pieces into the forefront of music. (For example, some violists find the extensions in the Schnittke concerto to be too extreme.) That doesn't mean that those pieces don't deserve study, they just may not be the right piece for you, or for you right now, or for you with your current instrument. Another example might be an orchestra or opera company planning to do a Ring Cycle performance, which is a huge undertaking for any instrumentalist. The rehearsal schedule alone might be very taxing, let alone the music itself, especially if you have never played them before and are learning the repertoire for the first time. In addition, performers are not usually in charge of rehearsal time usage, which can repeat taxing passages over and over, with little regard to how that affects the hands, arms, or body. Even if you're doing your best to take care of yourself, the repertoire, concert schedule, rehearsal schedule, or audition list might be too much for you, either now or in general.
If you've been injured, reflect on what it was that may have caused or exacerbated the injury- which categories were applicable? Having an awareness of these categories can certainly prevent future injuries, especially if you know what previously caused an injury.