There’s two different ways to have one leg “shorter than the other”. The first is to actually have one leg shorter than the other - that is, if you took an x-ray and measured the tibia, fibula and femur, you’d have one measurement less than the other. This is actually rare, but not unheard of.
The more common condition is called a “functional” leg difference, and what this means is that while the bones are the same length, one leg is hiked up tighter into the pelvis by a bunch of tight muscles, so when you measure your leg with a tape measure, one is longer than the other.
Obviously, a functional leg difference caused by tight pelvic or gluteal muscles will often be seen along with a foot pointing out - also caused by tight pelvic or gluteal muscles.
So a functional leg shortness doesn’t cause foot rotation, but the two are often caused by the same thing, and seen together. The treatment for both is massage and physical therapy, along with gait re-training and perhaps biofeedback to learn when you’re clenching.
My left foot naturally points outwards, partly due to being extremely flat-footed (which causes a roll inwards) and partly because at some point the tendon (maybe wrong term) that grabs the inside of the foot came halfway loose and never made a good grip again. Every roll would put pressure on that irritated end, and the tendon wasn’t pulling my foot forward as strongly as usual, so I unconsciously rotated my foot outwards to keep the roll from putting as much pressure on the end. By the time it was really noticed as pathological and we had a podiatrist look at it I was dragging it beside me, pointing straight out to the left, and never noticing anything was wrong.
Incidentally, this tendon-letting-go thing is not that uncommon a phenomenon in people over 65 or so. Seeing it developed like that in a 12-year-old, however… my doctor (as it happened then-president of some podiatrist’s association or another) had never seen it happen and had no idea what could have caused it.
So now I’ve got inserts I use sporadically in sneakers, or I wear paratrooper boots (with a black suit, no less) for the ankle support, or I just make a conscious effort to walk on the outsides of my feet.
I’m in the same camp as butler1850 and AHunter3 - left foot and leg are normal, right foot points out at an angle of about 30°. Right knee also points outward.
It’s not related to an accident or anything - been that way as long as I can remember, and some of the other members of my mother’s family had the same thing.
It’s never been a problem for me, but it means I don’t enjoy running for any length of time, because the weight comes down wrong on my right leg and foot - most of the impact is on the outside edge of my right foot, rather than evenly distributed.