@Dainty, could you please give me a real quick definition/idea of what you mean by "structural issues" here?
Great question. Not so simple to answer, but I'll do my best.
There are many things that fall under this broad category. The most obvious example most people are familiar with is bones being out of alignment. Lesser known examples would be bones being the wrong shape, or bones being way harder than they're supposed to be. The first time my current osteo felt my head, he turns and tells my then caregiver: "She's
literally hard-headed." If bones are too hard, or the wrong shape, it can cause a lot of strain on the body. With osteopathy, bones can soften back up again and literally change their shape back to what works for the body. My boyfriend's ribcage is actually pretty significantly deformed from countless street fights in his earlier days, it's visually shocking to anyone who saw it. Osteopathy is restoring his ribcage to normalcy. It's incredible to witness (and extremely painful for him, at times!)
But that's not the only kind of structural issue. The fascia is incredibly important to pretty much all functions of the body. It envelopes every organ, muscle, bone, etc and carries lymph fluids and makes sure things glide against each other smoothly. Lots of other important functions I'm not remembering at the moment. Fascia can get "wrinkles" in it, if you can imagine how saran wrap gets wrinkly and sticks to itself. When that happens with fascia, it causes problems. I have fascia adhesions in my abdomen, which results in abdominal tightness, G.I. emergencies that send me to the hospital, severe menstrual cramps, etc.
Fascia can also simply be stretched too thin or too tightly over an area, because it's being pulled by a structural problem elsewhere. So for example, I've read that people with carpal tunnel syndrome often have strains in their torso literally pulling the fascia like a long sleeve shirt, so that it's stretched tight against the wrists. Combine that with a lot of repetitive use, and you have carpel tunnel.
Finally, there's this thing called the Primary Respiratory Mechanism. It's a "pulse" that originates in the cerebralspinal fluid in your spine and head, and radiates to the rest of the tissues of the body. it is believed to play a very significant role in the body's self-healing and health maintenance. It's controversial, but whatever. Osteopaths feel for this pulse. If there's any part of the body where they cannot feel this pulse, they know there is some structural issue blocking the pulse from reaching that part of the body. Just like if someone had a severe injury to their arm, you would feel for a pulse and try to determine where the issue is affecting the pulse. the goal is to restore natural flow and movement.
Without movement, the human body locks up and begins adhering to itself. If you immobilized a joint long enough, the joint would freeze, right? imagine that happening in various ways, all over your body. The "pulse" of the primary respiratory mechanism gives regular movement on a very small level to all the tissues in the body, or at least it's supposed to. And when that gets blocked by trauma, be it physical or emotional, be it acute or chronic, or whatever, then lots of things can go haywire.
My legs were, to quote my osteo, "dead". The "pulse" of the primary respiratory mechanism hadn't reached them for a very, very long time.
A final point: osteopaths don't try to treat all structural issues. Only the ones that are actively causing problems. They can tell if it's a strain on the body or not, unlike many other structural modalities (e.g. chiropractics). Also, osteopathy isn't about fixing the body. It's about supporting the body's efforts to fix itself. So rather than move a bone into place, the osteo might gently work the soft tissue around the bone in such a way that frees it up, and 2 days later as I get up from a chair suddenly the bone pops into place all on its own. It's so freakin' cool.
I hope that helped, sorry for the length!