Although bone mineral density (BMD) is used to diagnose osteoporosis, it does not determine bone strength. Moment of inertia (MI) predicts 70–80% of bone strength. In animal models and young patients, the positive relationship between bone strength and muscle strength has been demonstrated by the thickness of the muscle in computerized tomography (CT). However, isokinetic dynamometry has not been widely used to analyze this interaction. The aim of this research was to analyze the correlation between muscle strength and power measured by isokinetic dynamometry, with bone resistance measured by MI and BMD, in patients with (PWO) and without osteopenia (PWoO).

Forty postmenopausal women were included (45–65 yo); 23 PWO and 17 PWoO. BMD was determined by X-ray dual densitometry; MI was determined by hip CT at femoral neck (MIFN), intertrochanteric region (MIIT) and femoral diaphysis (MIDiaf). Strength (inN/m) and muscle power (inW) was estimated in quadriceps, hamstrings, psoas, gluteus maximus, adductors and gluteus medius bilaterally. Correlation analysis was performed between strength and power with MI and BMD, and between groups. Coefficient of variation in isokinetics was verified.

Significant differences between groups in left gluteus medius strength were found (P=0.007) being higher in PWoO. Significant correlations (Table 1) were showed in PWoO with strength in quadriceps bilaterally, left hamstrings, psoas and adductors; strength in PWO correlated in psoas bilaterally and left gluteus medius. Power show significant correlation (Table 2) with PwoO in quadriceps and gluteus medius bilaterally, left hamstrings, psoas and adductors; for PWO in psoas bilaterally and left gluteus medius.

MI correlated with muscle strength and power. Correlation of strength and power was predominant in PWoO (83 versus 33% of muscles evaluated) on the ipsilateral side. No differences in power between groups were found.