Also, don't just think of this in terms of the spine.
A couple of other examples include (again teenagers)...
1) Patient, forearm/elbow/wrist pain, presented much like lateral/medial epicondylitis (can't remember which); upon significant questioning, and after several treatments in which she returned with no change, I found out her symptoms were stemming from PROLONGED playing of Guitar Hero (3-4 hours at a time). Once we limited playing time, her symptoms went away.
2) Patient, bil knee pain, primarily c/o pain following prolonged standing or prolonged sitting. Upon observation, it was seen that the patient during standing demonstrated significant hyperextension bil. Then with further questioning, when she sat in class, she propper her feet up on the chair in front of her, again her knee hyperextended. So we educated her on this and her pain went away.
3) Patient presented w/ TMJ pain. Patient presented w/ bruxism (grinding teeth) basically all the time. I instructed her in some relaxation techniques, educated her on this, and she got >50% relief alone in just a few days when she was informed of this.
Remember, posture isn't just spine posture. It plays a part in most, if not all musculoskeletal injuries. You can be the best at understanding symptoms, and treating a patient, but if you don't understand what is causing this patient to have their (typically) chronic symptoms, because of course, you as the PT are the last course of treatment is many cases, then your treatments will not last and be successful.