|
|
|
Progress in osteoarthritis:
A summary of recent Arthritis Foundation supported
research
David T. Felson, MD, MPH
Boston University
Osteoarthritis (OA) is the most common form of arthritis, and for many affected
persons with pain in their knees and hips, it is a frustrating disorder. There
are not many effective therapies, and none have been identified which prevent
the progression of disease. Recent research has generated exciting advances in
our understanding of what factors propel disease progression. Understanding the
reasons for disease progression might identify treatment targets. Also, if
people who are going to experience rapid disease progression could be
identified, we could study them in trials of potential therapies.
Recent Findings
The one factor that has emerged as critical in our understanding of
osteoarthritis progression is malalignment, in which the leg bones don’t
line up evenly at the knee joint (see Figure 1). One type of malaligned knee is
bowlegged (turned outward), whereas the opposite is knock-kneed (turned inward).
In both cases, during walking, stress or loading is not evenly distributed
across the knee joint. Researchers in the last few years have used MRI (magnetic
resonance imaging) findings, physical examination tests, and other evidence to
identify knees that are malaligned and to prove that malaligned knees are more
likely to progress rapidly than knees that are not malaligned. For instance, MRI
scans in persons with malaligned knees show that they have abnormalities (called
lesions) in the bone underneath the cartilage, suggesting that the bone has been
injured by the stress of malalignment. If the knee is bowlegged, which increases
stress across the inner aspect of the knee, there is often a bone lesion on that
same side. Knees with bone lesions are especially likely to experience cartilage
loss.
Malalignment can be evaluated during standing or walking. During walking, we
tend to load the inner aspect of our knees far more than the outer part, even if
our knees do not necessarily appear to be malaligned. People who excessively
load the inner aspect of their knees have a higher risk for developing knee
pain. Furthermore, the presence of malalignment during walking predicts a high
rate of progression. Doctors can check to see if the knees become malaligned
during walking by simply watching how patients walk.
Malalignment is such a powerful factor, it is likely that other disease risk
factors affect the knee differently depending on the state of alignment. For
example, obesity is an important risk factor affecting knee arthritis, but it
does not affect the risk of disease progression the same in all knees. In
severely knock-kneed or bowlegged knees, disease progression occurs whether the
person is obese or not. However, among persons who are just a little bowlegged
or knock-kneed, obesity accelerates disease progression.
Similarly, while quadriceps (thigh muscle) strengthening is an important and
effective treatment for knee OA, quadriceps that are too strong may actually
worsen the disease in a joint that is very malaligned. While this may be
frightening, it should not discourage patients from exercising and making their
muscles stronger as these activities will probably improve their symptoms.
Quadriceps strengthening may also prevent symptoms of joint instability that are
extremely common in patients with knee arthritis such as knee buckling, giving
way and even falling.
A Look Ahead
The recognition that malalignment is so critical in influencing progression of
disease makes possible treatments to improve alignment. A variety of strategies
may effectively straighten the knee and lessen the malalignment. These may
include slower walking or walking with toes rotated outward. Other strategies
being developed offer great promise. The new insights into the importance of
malalignment have offered new hope in our understanding of why patients
experience disease progression and how this might be prevented.
  
|
