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.

Quadriceps strength in women with radiographically progressive osteoarthritis of the knee and those with stable radiographic changes

OBJECTIVE

To explore the relationship between lower extremity weakness and the progression of established radiographic changes of knee osteoarthritis (OA).

METHODS

The study cohort of 342 elderly subjects was recruited from central Indiana by random digit dialing. We analyzed 79 subjects who had definite radiographic changes of unilateral or bilateral knee OA at baseline and for whom baseline data for lower extremity muscle strength and lean tissue mass and baseline and followup assessments of knee pain were available. Radiographs were graded for severity of OA at baseline and again about 2.5 years later (mean 31.5 months). Knee pain was evaluated at the same examination. Strength of the knee flexors and extensors was assessed bilaterally at baseline by isokinetic dynamometry and lower extremity muscle mass by dual energy x-ray absorptiometry.

RESULTS

Mean peak knee extensor strength of women with progressive OA, before and after adjustment for lower extremity muscle mass, was about 9% lower than that in those with stable radiographic changes, but this difference was not statistically significant. No difference was apparent between the 2 groups with respect to knee flexor (hamstring) strength. The decrease in quadriceps strength among women with progressive OA, relative to those with stable OA, did not appear to be attributable to knee pain, and knee extensor strength at baseline bore no apparent relationship to the development or progression of knee pain among those with OA.

CONCLUSION

We have shown previously that quadriceps weakness may be of etiologic importance in development of knee OA. The absence of a significant difference in quadriceps strength between subjects with radiographically stable OA and those whose joint damage progressed suggests that factors other than quadriceps weakness are more important determinants of OA progression.

Reduced quadriceps strength relative to body weight: a risk factor for knee osteoarthritis in women?

OBJECTIVE

To determine whether baseline lower extremity muscle weakness is a risk factor for incident radiographic osteoarthritis (OA) of the knee.

METHODS

This prospective study involved 342 elderly community-dwelling subjects (178 women, 164 men) from central Indiana, for whom baseline and followup (mean interval 31.3 months) knee radiographs were available. Lower extremity muscle strength was measured by isokinetic dynamometry and lean tissue (i.e., muscle) mass in the lower extremities by dual x-ray absorptiometry.

RESULTS

Knee OA was associated with an increase in body weight in women (P = 0.0014), but not in men. In both sexes, lower extremity muscle mass exhibited a strong positive correlation with body weight. In women, after adjustment for body weight, knee extensor strength was 18% lower at baseline among subjects who developed incident knee OA than among the controls (P = 0.053), whereas after adjustment for lower extremity muscle mass, knee extensor strength was 15% lower than in the controls (P not significant). In men, in contrast, adjusted knee extensor strength at baseline was comparable to that in the controls. Among the 13 women who developed incident OA, there was a strong, highly significant negative correlation between body weight and extensor strength (r = -0.740, P = 0.003), that is, the more obese the subject, the greater the reduction of quadriceps strength. In contrast, among the 14 men who developed incident OA, a modest positive correlation existed between weight and quadriceps strength (r = 0.455, P = 0.058). No correlation between knee flexor (hamstring) strength and knee OA was seen in either sex.

CONCLUSION

Reduced quadriceps strength relative to body weight may be a risk factor for knee OA in women.

Prevention of hip fractures: risk factor modification

Factors that influence the risk of hip fracture have been identified, many of which can be eliminated or modified. Even those risk factors that cannot be modified are important for identifying at-risk patients, who may benefit most from therapies that after other risk factors. Bone mineral density (BMD) is the major measurable determinant of the risk of fragility fractures. However, recent prospective studies have identified factors that influence the risk of having a hip fracture independently of the risk associated with low BMD. Skeletal factors other than BMD that may increase the risk of hip fracture in women include hip geometry and height (tallness). Other factors, some of which are potentially modifiable, operate through effects on the risk of trauma, including decreased visual acuity, neuromuscular impairment, cognitive impairment, residence in a nursing home, poor general physical health, and use of medications that diminish alertness. Fall mechanics also play an important role in the etiology of hip fractures. Falls to the side, particularly those with impact on the hip or side of the leg, more often result in hip fractures than do other falls. Protection of the hip with external padding offers great promise in the prevention of hip fracture in patients with very low bone mass or with conditions that make falls almost inevitable. Increases in hip fracture rates in developing countries suggest a possible relationship with declining physical activity (particularly load-bearing activity). Although the role of exercise in the prevention of osteoporosis and hip fracture has not yet been proven, there is evidence of independent protective effects of both past physical activity and moderate levels of recent physical activity on the risk of hip fracture. Low body weight secondary to poor appetite or poor health (as opposed to intentional weight loss) has been associated with increased hip fracture risk, and nutritional deficiencies may also play a role in hip fracture pathogenesis. These are potentially modifiable. Future studies should be aimed at confirming the hip fracture risk factors identified, ascertaining their independence from other factors, assessing their prevalence, and determining the outcomes and costs involved in interventions to modify them.

Quadriceps weakness and osteoarthritis of the knee

BACKGROUND

The quadriceps weakness commonly associated with osteoarthritis of the knee is widely believed to result from disuse atrophy secondary to pain in the involved joint. However, quadriceps weakness may be an etiologic factor in the development of osteoarthritis.

OBJECTIVE

To explore the relation between lower-extremity weakness and osteoarthritis of the knee.

DESIGN

Cross-sectional prevalence study.

SETTING

Population-based, with recruitment by random-digit dialing.

PARTICIPANTS

462 volunteers 65 years of age or older.

MEASUREMENTS

Radiographs of the knee were graded for the presence of osteoarthritis. Knee pain and function were assessed with the Western Ontario and McMaster Universities Arthritis Index, the strength of leg flexors and extensors was assessed with isokinetic dynamometry, and lower-extremity lean tissue mass was assessed with dual-energy x-ray absorptiometry.

RESULTS

Among participants with osteoarthritis, quadriceps weakness, but not hamstring weakness, was common. The ratio of extensor strength to body weight was approximately 20% lower in those with than in those without radiographic osteoarthritis. Notably, among women with tibiofemoral osteoarthritis, extensor weakness was present in the absence of knee pain and was seen in participants with normal lower-extremity lean mass (extensor strength, 30.1 lb-ft for those with osteoarthritis and 34.8 lb-ft for those without osteoarthritis; P < 0.001). After adjustment for body weight, age, and sex, lesser quadriceps strength remained predictive of both radiographic and symptomatic osteoarthritis of the knee (odds ratio for prevalence of osteoarthritis per 10 lb-ft loss of strength, 0.8 [95% CI, 0.71 to 0.90] for radiographic osteoarthritis and 0.71 [CI, 0.51 to 0.87] for symptomatic osteoarthritis).

CONCLUSION

Quadriceps weakness may be present in patients who have osteoarthritis but do not have knee pain or muscle atrophy; this suggests that the weakness may be due to muscle dysfunction. The data are consistent with the possibility that quadriceps weakness is a primary risk factor for knee pain, disability, and progression of joint damage in persons with osteoarthritis of the knee.

Sex steroids, bone mass, and bone loss. A prospective study of pre-, peri-, and postmenopausal women

Although bone loss around the time of menopause is driven by estrogen deficiency, the roles of estrogens and androgens in the preservation of skeletal mass at other stages of life are less well understood. To address this issue we studied 231 women between the ages of 32 and 77 with multiple measurements of sex steroids and bone mass over a period of 2-8 yr. In all women bone mass was negatively associated with concentrations of sex-hormone binding globulin, and positively associated with weight. Bone loss occurred from all skeletal sites in peri- and postmenopausal women, but premenopausal women lost bone only from the hip (-0.3%/yr) and had positive rates of change in the radius and spine. Bone loss was significantly associated with lower androgen concentrations in premenopausal women, and with lower estrogens and androgens in peri- and postmenopausal women. Sex steroids are important for the maintenance of skeletal integrity before menopause, and for as long as 20-25 yr afterwards.

Peak bone mass in young women

Increasing peak bone mineral density (BMD) or content (BMC) in young women may help to reduce the incidence of osteoporosis. Identifying the age when peak bone content or density is attained is essential to develop strategies aimed at optimizing peak BMD and BMC. Total body bone mineral density (TBBMD) and content (TBBMC) were measured by a dual X-ray absorptiometer in healthy females (n = 247, aged 11-32 years). TBBMD and TBBMC were modeled separately as a nonlinear function of age. By age 22.1 +/- 2.5 years, 99% of peak BMD is attained, and by age 26.2 +/- 3.7 years, 99% of peak BMC is attained. Nonlinear relationships between weight and TBBMD or TBBMC were also modeled. In this model, the influence of several parameters, including age, weight, and height, on BMC and BMD were simultaneously assessed. A model with age and weight described the best fit for TBBMD, whereas age, weight, and height described the best fit for total body TBBMC.

Genetic and behavioral influences on body fat distribution

Genetic and environmental influences on four measures of body fat distribution - subscapular/triceps ratio (STR), waist/hip ratio (WHR), and regression-adjusted subscapular skinfold and waist circumference indices - were examined in 265 pairs of white male twins, ages 59 to 70 years, who participated in the third examination of the National Heart, Lung, and Blood Institute's Twin Study. Skinfold indices of fat distribution were not highly correlated with indices based on body circumferences (r = 0.26-0.37 for the four possible correlations). After adjustment for overall obesity, the heritability of the adjusted subscapular skinfold index was substantial (h2 = 0.60, P less than 0.001), as were estimates for both subscapular and tricep skinfolds individually. By contrast, heritability of the STR was low and of borderline statistical significance (h2 = 0.24, P = 0.06). Heritability for the WHR (h2 = 0.31, P = 0.07) was also low. Although higher estimates were observed for the adjusted waist circumference index (h2 = 0.46, P = 0.02) and for the component circumferences, these were not clearly due to genetic influences. Among behavioral influences, cigarette smoking was strongly related to the WHR and adjusted waist circumference index (P less than 0.0001). A crude measure of total physical activity was weakly, inversely related to WHR (P = 0.06), and slightly more strongly related to the adjusted waist circumference index (P = 0.01). Skinfold indices were unrelated to either behavior. We conclude that: (1) skinfold indices measure a different dimension of fat distribution than circumference indices; (2) there is evidence for a genetic influence on subcutaneous fat distribution, but less evidence for such an influence on the WHR; (3) behavioral factors appear to be more important in determining the WHR than subcutaneous fat patterning.

Calcium absorption from calcium carbonate and a new form of calcium (CCM) in healthy male and female adolescents

Calcium absorption from two Ca salts was investigated in a crossover design using stable isotopic tracers in 12 healthy adolescents (6 males, 6 females). A Ca supplement in the form of Ca carbonate or Ca citric and malic acids (CCM) was ingested with a standardized breakfast and the order of administration was randomized. The oral supplement contained 250 mg elemental Ca, 21.8 mg of which was highly enriched 44Ca tracer. Thirty minutes later subjects received 3.6 mg 42Ca tracer intravenously. The molar concentrations of 42Ca and 44Ca tracers in a urine sample obtained 24 h after tracer administration were quantified by fast-atom-bombardment mass spectrometry and used to determine fractional absorption of the Ca from the supplement. Ca in the form of CCM had an increased fractional absorption (p less than 0.03) relative to Ca carbonate in healthy adolescents (36.2 vs 26.4%). This increase was not related to body size, sex, or indices of Ca metabolism.

Sex steroids and bone mass. A study of changes about the time of menopause

To examine the relationships between bone loss and sex steroids, 84 peri- and postmenopausal women were studied at 4-mo intervals for 3 yr. At each visit, measurements were made of bone mass at the midshaft and distal radius, of steroids, of gonadotropins, and of bone gla protein (BGP). Bone loss was approximately 1% per yr among late perimenopausal and postmenopausal groups, whereas the early perimenopausal group lost no bone. Mean serum estrogen and BGP concentrations predicted rates of bone loss. BGP was negatively correlated with the rate of bone loss (r = -0.45) and with mean estrogen concentrations (r = -0.40). Multivariate regressions showed estrogen concentrations to be strong independent predictors of the slope of bone mass over time. When BGP concentrations were added to the models, the significance of estrogen was reduced, suggesting that a portion of the estrogen effect was mediated through effects on rates of bone remodelling.

Concordance for type 2 (non-insulin-dependent) diabetes mellitus in male twins

Concordance for Type 2 (non-insulin-dependent) diabetes was determined in 250 monozygotic and 264 dizygotic white male twin pairs who participated in the National Heart, Lung, and Blood Institute Twin Study. These twins were born between 1917 and 1927 and were identified from military records without regard to disease status. We examined surviving members of the cohort twice--at mean ages of 47 and 57 years--and obtained 1-h post-load glucose tests and medication histories. Diagnostic criteria for Type 2 diabetes included a glucose value greater than or equal to 13.9 mmol/l or current use of antidiabetic medication; possible Type 1 (insulin-dependent) diabetic twins were excluded. A strong genetic predisposition to Type 2 diabetes was suggested by 3 lines of evidence from the second examination: (1) 58% of monozygotic co-twins of diabetic twins were themselves diabetic compared with an expected prevalence of 10%; (2) only 1 of 15 originally disease-discordant, monozygotic twin pairs remained discordant for diabetes; and (3) 65% of non-diabetic monozygotic co-twins of diabetic twins had elevated glucose values. Because concordance for diabetes was less than 100% for twins aged 52-65 years and because twins varied in age at onset of disease, non-genetic factors may also influence diabetes development. Among the 19 monozygotic twins pairs discordant for diabetes, diabetic twins did not differ from their non-diabetic co-twins in obesity, diet, alcohol consumption, or education. However, compared with unrelated non-diabetic twins of the same ages, non-diabetic co-twins of diabetic twins gained more weight as adults (p less than 0.02) and had higher glucose levels (p less than 0.03).