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Any busy primary care clinician sees osteo-arthritis or degenerative joint disease (DJD) of the knee if they see elderly patients. Knowing the etiology and therefore some preventive strategy could prevent the associated morbidity and mortality of knee DJD.
By finding 462 volunteers aged 65 years or older using a random digit dialing technique, Slemenda and colleagues first sorted out whether the patients had clinical osteoarthritis or x-ray evidence of DJD. They conducted strength testing and sophisticated statistical analysis and then corrected for body weight, age, and gender and were able to predict that if weakness in the quadriceps was present, there was radiological or symptomatic DJD of the knee. By doing subanalysis of unilateral arthritis, they were able to predict the same. Their evaluations included sophisticated Western Ontario and McMasters Universities Arthritis Index, concentric and eccentric isokinetic dynamometer, as well as radiographs and dual x-ray absorptiometry. They examined the association between strength and DJD in persons with both x-ray evidence of DJD and no knee pain, x-ray evidence of DJD with knee pain, or no x-ray evidence with knee pain or both. The association held true.
Slemenda and colleagues freely admit that very little is known about quadriceps weakness developing in DJD of the knee. What I as a practicing clinician find most fascinating is that their results could be consistent with quadriceps weakness preceding the development of knee pain and disability. Therefore, it could be part of the pathogenic process. This may actually make sense as I reflect on it clinically. My patients who are elderly and who are big walkers are not generally the patients that come in complaining of knee arthritis (the runners are an exception, their intermittent rapid loading of the knee joint may contribute to the DJD). It’s the patients who are less active who complain, and this might be the downward spiral of quadriceps weakness affecting DJD and vice versa. As Slemenda et al call for, I think it would be interesting to do a study in a randomized, placebo-controlled trial on whether exercise can be used to strengthen quadriceps and slow the progression of pathologic changes of DJD or even reduce the risk of disability due to DJD of the knee.
This is exciting. Imagine preventing osteoarthritis by a walking regimen instituted in the 40s or 50s. This would be more fuel for the fire of the President’s council recommendation on activity in the American population. Let’s all start walking.