Fabian E. Pollo, PhD and Robert W. Jackson, MD had a study entitled:'Knee Bracing for Unicompartmental Osteoarthritis' published in The Journal of the American Academy of Orthopaedic Surgeons.
To quote their summary:
"Unicompartmental osteoarthritis of the knee affects millions of individuals. Most nonsurgical management of this progressive disease is primarily directed at reducing inflammation and pain with medication. Evidence supports the clinical efficacy of bracing for managing osteoarthritis of the knee. In some patients, bracing significantly reduces pain, increases function, and reduces excessive loading to the damaged compartment. A variety of health and functional status instruments, as well as radiologic techniques and biomechanical investigations, has been used to evaluate the unloading capabilities of these braces. Although changes in angulation are relatively minimal, the braces have been shown to load share and thus reduce the stresses in the degenerated medial compartment of the knee."
That is, they do as promised and are a valuable tool in the fight against arthritic knee pain.