Do not bend over to pick up; lift with your knees, back straight. This includes lifting your instrument with or without the case. Even if you use backpack-style straps, you still want to get low, lift with your knees, and then position the pack. Balanced body position matters even if you are towing with a case on wheels. Again you need to work out how to walk with your back as straight as possible, even while dragging.
Next, there is body position while sitting to consider.
The most natural, least damaging position while seated is to have your knees almost at the ninety-degree position. Knees spread to about shoulder width, back straight. Much if not all activity for your bowing arm should start with the wrist position. And the rest of the arm should be comfortable and fluid with the motions following the wrists' lead. Don't become a statue in the chair; you need to move for your body to contour to the wrists' positions around the instrument.
*Warning* Like an athlete, playing puts a strain on your body and can cause repetitive motion injuries. You should always stretch before playing. And if you are to practice or perform for an extended period, there needs to be a moment where you can stretch your legs and do your stretches once more. Occasionally practicing in front of a mirror and witnessing your body positions while playing is also a good idea.
You must review your body positions affecting the injured area if you find yourself in pain during or after a practice or performance.
Apply ice to the injured area, being careful not to induce a freezer burn to your skin from the pack. Put a t-shirt weight material between the ice pack and the skin.
Hydrate! it may not be your first thought about muscle, ligament, and joint injuries, but lubrication is a by-product of your body's moisture. If you dehydrate, you are at greater risk of motion incurred injury.
