In December 2015 a study was published in JOSPT (The Journal of Orthopaedic and Sports Physical Therapy) confirming that the inclusion of manual therapy to an exercise program for patients with knee osteoarthritis boosted the effects.
This is not news to a manual therapist or hands on practitioner (such as Physiotherapists who have attained the FCAMPT designation, or become a specialist in manual therapy).
Every joint with arthritic/degenerative change also demonstrates impairments in the muscle tissue surrounding that joint. With knee osteoarthritis this usually involves shortening/tightening of the quadriceps muscle which reduces the strength and effectiveness of this muscle in addition to altering force transmission through the joint in a negative way. Hands-on tissue work is a complement to exercise in this scenario.
For more information, consult the journal directly.