Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


Thigh Muscle Quality Correlates with Function, Leg Strength, and Walking Speed, but Not with Alignment in Individuals with Obesity and Knee Osteoarthritis.

Holt3,  Rachel W., Loeser5,  Richard F., Davis4,  Cralen, Legault4,  Claudine, Nicklas4,  Barb, Carr4,  Jeffrey, Hunter1,  David J.

New England Baptist Hospital, Boston, MA
Wake Forest Univ, Winston-Salem, NC
Wake Forest Univ., Winston Salem, NC
Wake Forest Univ.
Wake Forest University, Winston-Salem, NC

Purpose:

The effect of obesity on risk for disease progression in osteoarthritis is mediated by the extent of malalignment but it is not known if adiposity and alignment are related. Adipose tissue in the thigh varies in distribution with some individuals having greater subcutaneous fat and others more between (intermuscular) and within (intramuscular) adipose tissue. In addition, muscle associated triglyceride can be determined by the CT attenuation of muscle and is a measure of muscle quality. The objective of this study was to determine the relationship between CT measures of thigh fat and lower extremity alignment and then with measures of pain and function in overweight and obese adults with mild to moderate knee OA.

Methods:

Data were collected at baseline from participants entering the Intensive Diet and Exercise for Arthritis (IDEA) study. Inclusion criteria were BMI of 27–40.5 kg/m2, age>55 years, self reported disability due to knee pain, and radiographic evidence of mild to moderate (K-L score II-III) tibiofemoral OA in at least one knee. Mechanical alignment was measured using full-length lower extremity x-rays and Image J software. Subcutaneous and inter/intramuscular (IM) thigh adipose tissue and thigh muscle quality were measured by CT. Self reported pain and function were evaluated using WOMAC. Strength was measured on a Kin-Con isokinetic dynamometer. Data were analyzed using SAS to calculate Pearson correlation coefficients and ANOVA (for analysis of alignment type).

Results:

Data were available on 129 IDEA participants with the following characteristics: 70% female, mean±sd age of 65.9±6.2 years, BMI of 33.2±3.7 units, subcutaneous thigh fat of 876.2±285.9 cm3, IM thigh fat of 30.4±16.1 cm3, thigh muscle quality of 52.0±6.2 Hounsfield units, WOMAC function of 23.4 ±10.4, WOMAC pain of 6.0±2.9, concentric extensor strength of 61.2±23.9 Nm and 236.3±83.4 N, and walking speed of 1.2±0.2 m/s. 25% of the subjects had neutral alignment, 25% valgus, and 50% varus. The analysis of muscle quality showed significant negative correlations with age, BMI, IM thigh fat, and WOMAC function and positive correlations with strength and walking speed (Table 1). The analysis of the magnitude of the alignment angle (Table 1) revealed weak but significant correlations with WOMAC pain and function but not the CT measures. Furthermore, the mean thigh muscle quality did not differ significantly between the three alignment types (ANOVA not shown).

Conclusion:

These results suggests that reduced thigh muscle quality due to IM fat correlates with age and BMI and has a detrimental effect on strength, speed, and overall function in this population; however, alignment does not appear to have the same impact. Based on posthoc power calculations, a larger sample size would be needed to detect the observed differences of about 1 HU in thigh muscle quality between alignment types.

  Quadriceps qualityAlignment (angle)
VariableNrprp
Age129-0.310.00030.020.86
BMI129-0.190.040.130.15
Subcutaneous thigh fat (cm2)129-0.180.04-0.0010.99
IM thigh fat (cm2)128-0.310.00020.020.86
Quadriceps quality129  -0.030.71
WOMAC pain129-0.040.630.250.01
WOMAC function129-0.190.030.180.04
Leg strength (Nm)1020.260.01-0.020.86
Leg strength (N)1020.300.003-0.040.67
6 minute walk speed1290.200.02-0.130.15

To cite this abstract, please use the following information:
Holt, Rachel W., Loeser, Richard F., Davis, Cralen, Legault, Claudine, Nicklas, Barb, Carr, Jeffrey, et al; Thigh Muscle Quality Correlates with Function, Leg Strength, and Walking Speed, but Not with Alignment in Individuals with Obesity and Knee Osteoarthritis. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :203
DOI: 10.1002/art.27972

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