A comparison of lower extremity muscle strength, obesity, and depression scores in elderly subjects with knee pain with and without radiographic evidence of knee osteoarthritis

Objective. To determine, in subjects with knee pain but no radiographic changes of tibiofemoral or patellofemoral compartment osteoarthritis (OA), whether mean body weight, quadriceps and hamstring strength, lower extremity muscle mass, depression scores, and perceptions of their general health status differed from those of subjects with symptomatic knee OA. Methods. Subjects were 25 women and 10 men with knee pain and radiographic evidence of OA at the baseline examination, and 21 women and 16 men who had knee pain at the baseline examination but no radiographic evidence of knee OA at either baseline examination or followup evaluation performed, on average, 31 months later. These individuals were a subset of a cohort of 462 independently living elderly individuals recruited by telephone interview after random selection through random digit dialing of households in central Indiana. Data from an additional 134 subjects who had neither knee pain nor radiographic changes of OA at either the baseline or followup examination were analyzed for comparison. Lower extremity muscle strength was measured by isokinetic dynamometry, lean tissue (i.e., muscle) mass in the lower extremities by dual x-ray absorptiometry, depression by Center for Epidemiology Depression (CES-D) scale, knee pain by Western Ontario McMaster University OA instrument, and perceived general health status by the Medical Outcome Survey Short Form-36. Results. in contrast to those with symptomatic knee OA, those who had knee pain but no radiographic evidence of OA were less obese, had hamstring as well as quadriceps weakness, and had CES-D scores high enough to qualify for a diagnosis of clinical depression. Conclusion. Among subjects with knee pain but no OA - and among women in this subset, in particular - knee pain may be a manifestation of depression, rather than of joint disease.