"Outcome is important to the ego, process is important to awakening"
Some of the most common conditions causing back pain are:
Subluxation, where the vertebra is out of place or fixated, stuck in a position (possibly out of place).
Muscular spasms, trigger points, fascial adhesions and a whole assortment of spinal muscle conditions that contribute to back pain. It is helpful to recognize that many of these muscles are on the anterior of the spine or in the pelvic region as well.
Those of us who love our physical yoga practice and that have been practicing for a long time have probably experienced some kind of discomfort or difficulty in the practice. This can be a low-level pain, a painful injury, an inability to physically comprehend an asana or a major setback in an asana that you could once do proficiently. The injury or setback could have come from poor technique but often is from functional problems with the structure of the body. Many of us have utilized chiropractic, massage, acupuncture, osteopathy or other healing modalities to remedy these situations.
Over the years I have heard some disparaging stories about Ashtanga yoga because of the intensity of the practice and the many stories of injuries. Part of the problem is that people with gifted bodies become teachers very quickly, not necessarily acquiring the intrinsic knowledge that is essential in a truly qualified teacher. It is easy to miss the forest for the trees as the body becomes impressively developed. Physically gifted neophytes are often more vulnerable to the ego running the program, whereas older, more experienced teachers have been humbled by time and practice.