Osteophytes and increasing knee bone size may be causally related to knee cartilage defects. Furthermore, knee cartilage defects may result in increased cartilage breakdown leading to decreased cartilage volume and joint space narrowing suggesting an important role for knee cartilage defects in early knee OA.

Background: Knee cartilage defects may play an important role in early osteoarthritis, but little is known about their natural history.Methods: Knee cartilage defect score (range, 0-4), cartilage volume, and bone surface area were determined using T1-weighted fat-saturated magnetic resonance imaging in 325 subjects (mean age, 45 years) at baseline and 2 years later.Results: Thirty-three percent of the subjects had a worsening (Ն1-point increase) and 37% of the subjects had an improvement (Ն1-point decrease) in cartilage defect score in any knee compartment during 2.3 years. A worsening in cartilage defect score was significantly associated with female sex (odds ratio [OR], 3.09 and 3.64 in the medial and lateral tibiofemoral compartments) and baseline factors, including age (OR, 1.05 per year in the medial tibiofemoral compartment), body mass index (OR, 1.08 in the lateral tibiofemoral compartment), tibiofemoral osteophytes (OR, 6.22 and 6.04 per grade), tibial bone area (OR, 1.24 and 2.07 per square centimeter), and cartilage volume (OR, 2.91 and 1.71 per milliliter in the medial tibiofemoral and patellar compartments). An improvement in cartilage defect score had similar but reversed associations with these factors (except for sex), including a decrease in body mass index (OR, 1.23 in the medial tibiofemoral compartment).Conclusions: Knee cartilage defects are variable, and changes are associated with female sex, age, and body mass index. Increases are associated with baseline cartilage volume, bone size, and osteophytes, suggesting a role for these in the pathogenesis of cartilage defects. Interventions such as weight loss may improve knee cartilage defects.

Objective. To describe the association between chondral defects, bone marrow lesions, knee and hip radiographic osteoarthritis (OA), and knee pain. Methods. Knee pain was assessed by the Western Ontario and McMaster Universities Osteoarthritis Index. T1-and T2-weighted fat saturation magnetic resonance imaging was performed on the right knee to assess chondral defects and subchondral bone marrow lesions. Radiography was performed on the right knee and hip and scored for radiographic OA. Body mass index (BMI) and knee extension strength were measured. Results. A total of 500 randomly selected men and women participated. The prevalence of knee pain was 48%. In multivariable analysis, prevalent knee pain was significantly associated with medial tibial chondral defects (odds ratio [OR] 2.32, 95% confidence interval [95% CI] 1.02-5.28 for grade 3 versus grade 2 or less; OR 4.93, 95% CI 1.07-22.7 for grade 4 versus grade 2 or less), bone marrow lesions (OR 1.44, 95% CI 1.04 -2.00 per compartment), and hip joint space narrowing (OR 1.36, 95% CI 1.07-1.73 per unit), as well as greater BMI and lower knee extension strength. It was not significantly associated with radiographic knee OA. These variables were also associated with more severe knee pain. In addition, there was a dose response association between knee pain and number of sites having grade 3 or 4 chondral defects (OR 1.39, 95% CI 1.12-1.73 per site), with all subjects having knee pain if all compartments of the knee had these defects. Conclusion. Knee pain in older adults is independently associated with both full and non-full-thickness medial tibial chondral defects, bone marrow lesions, greater BMI, and lower knee extension strength, but is not associated with radiographic knee OA. The association between radiographic hip OA and knee pain indicates that referred pain from the hip needs to be considered in unexplained knee pain. KEY WORDS. Knee pain; Chondral defects; Bone marrow lesions; Knee and hip radiographic OA.

DING, CHANGHAI, FLAVIA CICUTTINI, FIONA SCOTT, HELEN COOLEY, AND GRAEME JONES. Knee structural alteration and BMI: a cross-sectional study. Obes Res. 2005;13:350 -361. Objective: To describe the associations among BMI, knee cartilage morphology, and bone size in adults. Research Methods and Procedures:A cross-sectional convenience sample of 372 male and female subjects (mean age, 45 years; range, 26 to 61 years) was studied. Knee articular cartilage defect score (0 to 4) and prevalence (defect score of Ն2), volume, and thickness, as well as bone surface area and/or volume, were determined at the patellar, tibial, and femoral sites using T1-weighted fat-saturation magnetic resonance imaging. Height, weight, BMI, and radiographic osteoarthritis were measured by standard protocols. Results:In multivariate analysis in the whole group, BMI was significantly associated with knee cartilage defect scores (␤: ϩ0.016/kg/m 2 to ϩ0.083/kg/m 2 , all p Ͻ 0.05) and prevalence (odds ratio: 1.05 to 1.12/kg/m 2 , all p Ͻ 0.05 except for the lateral tibiofemoral compartment). In addition, BMI was negatively associated with patellar cartilage thickness only (␤ ϭ Ϫ0.021 mm/kg/m 2 ; p ϭ 0.039) and was positively associated with tibial bone area (medial: ␤ ϭ ϩ7.1 mm 2 /kg/m 2 , p ϭ 0.001; lateral: ␤ ϭ ϩ3.2 mm 2 /kg/ m 2 , p ϭ 0.037). Those who were obese also had higher knee cartilage defect severity and prevalence and larger medial tibial bone area but no significant change in cartilage volume or thickness compared with those of normal weight.Discussion: This study suggests that knee cartilage defects and tibial bone enlargement are the main structural changes associated with increasing BMI particularly in women. Preventing these changes may prevent knee osteoarthritis in overweight and obese subjects.

Hand OA at these two sites makes substantial contributions to hand function, strength and pain. The associations with function and strength measures appear mediated by pain. Gender differences in all three measures persist after adjustment for variation in age and OA severity indicating that factors apart from radiographic disease are responsible.