Patellar cartilage: T2 values and morphologic abnormalities at 3.0-T MR imaging in relation to physical activity in asymptomatic subjects from the osteoarthritis initiative

Abstract

Purpose: To study the interrelationship between patella cartilage T2 relaxation time, other knee abnormalities, and physical activity levels in asymptomatic subjects from the Osteoarthritis Initiative (OAI) incidence cohort.

Materials and methods: The study had institutional review board approval and was HIPAA compliant. One hundred twenty subjects from the OAI without knee pain (age, 45-55 years) and with risk factors for knee osteoarthritis (OA) were studied by using knee radiographs, 3.0-T knee magnetic resonance (MR) images (including intermediate-weighted fast spin-echo and T2 mapping sequences), and the Physical Activity Scale for the Elderly. MR images of the right knee were assessed by two musculoskeletal radiologists for the presence and grade of abnormalities. Segmentation of the patella cartilage was performed, and T2 maps were generated. Statistical significance was determined by using analysis of variance, chi(2) analysis, correlation coefficient tests, the Cohen kappa, and a multiple linear regression model.

Results: Cartilage lesions were found in 95 (79.0%) of 120 knees, and meniscal lesions were found in 54 (45%) of 120 knees. A significant correlation between patella cartilage T2 values and the severity and grade of cartilage (P = .0025) and meniscus (P = .0067) lesions was demonstrated. Subjects with high activity levels had significantly higher prevalence and grade of abnormalities and higher T2 values (48.7 msec +/-4.35 vs 45.8 msec +/-3.93; P < .001) than did subjects with low activity levels.

Conclusion: Middle-aged asymptomatic individuals with risk factors for knee OA had a high prevalence of cartilage and meniscus knee lesions. Physically active individuals had more knee abnormalities and higher patellar T2 values. Additional studies will be needed to determine causality.

Figure 1a:

Sagittal (a, c) two-dimensional T2-weighted first-echo MR images and (b, d) corresponding T2 maps show manually drawn region of interest (white outline) of patella cartilage as (a) originally drawn, which reveals cartilage quantification bias owing to fluid artifacts seen (b) when the T2 map is overlaid. Images c and d show region of interest corrected to exclude fluid artifacts.

Figure 1b:

Sagittal (a, c) two-dimensional T2-weighted first-echo MR images and (b, d) corresponding T2 maps show manually drawn region of interest (white outline) of patella cartilage as (a) originally drawn, which reveals cartilage quantification bias owing to fluid artifacts seen (b) when the T2 map is overlaid. Images c and d show region of interest corrected to exclude fluid artifacts.

Figure 1c:

Sagittal (a, c) two-dimensional T2-weighted first-echo MR images and (b, d) corresponding T2 maps show manually drawn region of interest (white outline) of patella cartilage as (a) originally drawn, which reveals cartilage quantification bias owing to fluid artifacts seen (b) when the T2 map is overlaid. Images c and d show region of interest corrected to exclude fluid artifacts.

Figure 1d:

Sagittal (a, c) two-dimensional T2-weighted first-echo MR images and (b, d) corresponding T2 maps show manually drawn region of interest (white outline) of patella cartilage as (a) originally drawn, which reveals cartilage quantification bias owing to fluid artifacts seen (b) when the T2 map is overlaid. Images c and d show region of interest corrected to exclude fluid artifacts.

Figure 2a:

Color-coded T2 maps overlaid on first-echo MR images obtained with multiecho SE sequence show (a)low patellar T2 values in a sedentary patient and (b) high patellar T2 values in an active patient of the same age.

Figure 2b:

Color-coded T2 maps overlaid on first-echo MR images obtained with multiecho SE sequence show (a)low patellar T2 values in a sedentary patient and (b) high patellar T2 values in an active patient of the same age.

Figure 3:

Mean patellar T2 values in subjects in low-activity (left, 1) and high-activity (right, 2) PASE groups (P < .001). Significance was determined by using a multivariate regression model. P value reflects a test of dependent T2 variable by ordinal PASE variable adjusted for sex, age, BMI, and OA risk factors.