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Pain in the knee. Knees seem to be among the most vulnerable of all joints. According to the American Academy of Orthopaedic Surgeons, more joint replacement surgeries are performed on the knee than on any other joint.

David T. Felson, a MED professor of medicine, has focused his research on osteoarthritis, a leading cause of joint pain and physical disability. In previous research he established a connection between genetic predisposition, joint injury -- either traumatic or through repetitive action -- and osteoarthritis. His current study, of disease in the knee joint, which appears in the September 2 issue of the Annals of Internal Medicine, looks at the connection between alignment, bone lesions, and knee pain.

The source of knee pain is complex. Most people think first of cartilage degradation as the cause of pain, but cartilage does not contain nerves. Felson used MRIs and knee radiography to examine the bones and bone alignment of patients with osteoarthritis of the knee. He and his team found that bone marrow edema lesions, abnormal changes in the internal structure of the bone, were strikingly related to the alignment of the bones in the leg. The authors caution, however, that it is not yet clear if the progression of the disease results from the lesions, or if malalignment produces both the lesions and increasing deterioration, pain, and stiffness. They further caution that since there is no current treatment for bone marrow edema, there is no need for routine MRIs to scan for bone lesions.

Seeing bones better. More than 250 million people worldwide suffer from osteoporosis, a disease that causes the bones to lose mass, leaving them weak and susceptible to fracture. Postmenopausal women are particularly at risk -- nearly 35 percent of them will fracture a hip, vertebra, or wrist, injuries that can have enormous medical costs and serious impact on quality of life.

Traditionally, bone density has been measured by a process known as X-ray densiometry, where the density of the bones is assessed through X rays. Although highly accurate, the procedure is expensive and exposes the patient to ionizing radiation. Emmanuel Bossy, a new postdoctoral research associate in the ENG department of aeronautical and mechanical engineering, has developed a new ultrasound technology to detect osteoporosis. The technology is nonionizing, portable, and inexpensive, and holds the promise not only of revealing bone density, but potentially of revealing elasticity, geometry, and internal architecture as well -- all indicators of bone strength and health.

In a series of in vitro experiments, Bossy first identified how differing characteristics of bone, and the soft tissue that surrounds it, influence the speed of a sound wave moving axially (along the length of the bone). By eliminating variations in speed that result from the sound waves passing through soft tissue of varying density, he was able to develop a prototype ultrasound device able to produce accurate measurements in human subjects. A clinical study is now being conducted using this prototype, which is designed for easy use in early diagnosis of osteoporosis during a routine checkup in a doctor’s office.

Bossy began working on this technology at the Laboratoire d’Imagerie Paramétrique, Centre National de la Recherche Scientifique/Université de Paris, where he received his Ph.D. He is continuing to refine the technology as a researcher at the Center for the Study of Subsurface Sensing and Imaging Systems (CenSSIS), applying methods used in bone characterization to problems such as assessing density in corals.

Bossy’s research was published in the Journal of the Acoustical Society of America in March 2002.

"Research Briefs" is written by Joan Schwartz in the Office of the Provost. To read more about BU research, visit


15 May 2003
Boston University
Office of University Relations