A fantastic article detailing the current scientific understanding of manual therapy and its limitations: http://www.truemovement.net/manual-therapies-make-space/
“I like to conceptualize the effects of hands on care as “making space.” People who seek massage or other manual therapies are typically having some kind of unpleasant experience they would like to distance themselves from, overcome, or adapt to. Because the application of skilled touch can provide short term pain relief, improvements in mood, reduced muscular tension, and improved range of motion, manual therapies can often create a sort of buffer from some of the factors that influence these experiences.
A great deal of common aches, injuries, stiffness, and other stressors will get better over time without intervention. While the nature of different conditions certainly influences the recovery period of these events, even some rather complicated disorders improve at about the same rate with or without treatment. The goal of manual therapy here is not to alter healing, but to make the natural process feel easier and more comfortable.”