August 15, 2016
Osteoarthritis and Cartilage/OARS, Osteoarthritis Research Society

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People aged 50 to 60 years with no evidence of knee osteoarthritis (OA) were followed for 48 months to assess the impact of thigh muscle strength on the progression of knee cartilage degeneration. Thigh extension strength was associated with thigh muscle cross-sectional area (CSA). There was a significant association seen between thigh muscle CSA and increase in cartilage whole organ MRI score (WORMS) in the patellar and trochlear compartments. The patellar cartilage increase in WORMS was associated with CSA of extensors and vastus medialis. The baseline extensor/flexor (E/F) ratio was significantly associated with an increase in patellar WORMS cartilage score.

The risk of patellofemoral cartilage deterioration is associated with the E/F ratio in the thigh. Cartilage loss may be accelerated by high extensor and vastus medialis CSA.

Abstract

OBJECTIVE

To determine in a 48-month longitudinal study the association of thigh muscle cross-sectional area (CSA) and strength on progression of morphologic knee cartilage degeneration using 3T magnetic resonance imaging (MRI).

DESIGN

Seventy Osteoarthritis Initiative (OAI) subjects aged 50-60 years, with no radiographic evidence of osteoarthritis (OA) and constant muscle strength over 48 months as measured by isometric knee extension testing were included. Baseline right thigh muscle CSAs were assessed on axial T1-weighted MR images, and extensor to flexor CSA ratios were calculated. Degenerative knee abnormalities at baseline and 48-months were graded on right knee 3T MRIs using a modified whole organ MRI score (WORMS). Statistical analysis employed Student’s t-tests and multivariable regression models adjusted for age, body mass index and gender.

RESULTS

Extension strength was significantly and positively correlated with baseline thigh muscle CSA (r=0.65, p<0.001). Greater baseline total thigh muscle CSA was significant associated with increase of cartilage WORMS scores over 48 months in patellar (p=0.027) and trochlear (p=0.038) compartments, but not in other knee compartments. Among specific muscle groups, CSA of extensors (p=0.021) and vastus medialis (VM) (p=0.047) were associated with patellar cartilage increase in WORMS. Baseline E/F ratio had a significant positive association with patellar WORMS cartilage score increase over 48 months, p=0.0015. There were no other significant associations between muscle CSA/ratios and increase in WORMS scores. CONCLUSION Maintenance of proper extensor to flexor muscle balance about the knee through decreased E/F ratios may slow patellofemoral cartilage deterioration, while higher extensor and VM CSA may increase patellofemoral cartilage loss. Journal Abstract
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