Weight loss in obese people has structure-modifying effects on medial but not on lateral knee articular cartilage

BackgroundObesity is an important risk factor for knee osteoarthritis (OA), Weight loss can reduce the symptoms of knee OA. No prospective studies assessing the impact of weight loss on knee cartilage structure and composition have been performed.ObjectivesTo assess the impact of weight loss on knee cartilage thickness and composition.Methods111 obese adults were recruited from either laparoscopic adjustable gastric banding or exercise and diet weight loss programmes from two tertiary centres. MRI was performed at baseline and 12-month follow-up to assess cartilage thickness. 78 eligible subjects also underwent delayed gadolinium-enhanced MRI of cartilage (dGEMRIC), an estimate of proteoglycan content. The associations between cartilage outcomes (cartilage thickness and dGEMRIC index) and weight loss were adjusted for age, gender, body mass index (BMI) and presence of clinical knee OA.ResultsMean age was 51.7±11.8 years and mean BMI was 36.6±5.8 kg/m2; 32% had clinical knee OA. Mean weight loss was 9.3±11.9%. Percentage weight loss was negatively associated with cartilage thickness loss in the medial femoral compartment in multiple regression analysis (β=0.006, r2=0.19, p=0.029). This association was not detected in the lateral compartment (r2=0.12, p=0.745). Percentage weight loss was associated with an increase in medial dGEMRIC in multiple regression analysis (β=3.9, r2=0.26; p=0.008) but not the lateral compartment (r2=0.14, p=0.34). For every 10% weight loss there was a gain in the medial dGEMRIC index of 39 ms (r2=0.28; p=0.014). The lowest weight loss cut-off associated with reduced medial femoral cartilage thickness loss and improved medial dGEMRIC index was 7%.ConclusionsWeight loss is associated with improvements in the quality (increased proteoglycan content) and quantity (reduced cartilage thickness losses) of medial articular cartilage. This was not observed in the lateral compartment. This could ultimately lead to a reduced need for total joint replacements and is thus a finding with important public health implications.

Delayed Gadolinium-Enhanced Magnetic Resonance Imaging of Cartilage: Clinical Associations in Obese Adults

Objective.Delayed gadolinium-enhanced magnetic resonance imaging (MRI) of cartilage (dGEMRIC) is used to assess cartilage glycosaminoglycan distribution. Our aim was to determine the relationships between self-reported pain and disability, clinical variables, and serum leptin, and dGEMRIC indices in obese subjects with and without clinical knee osteoarthritis (OA).Methods.Seventy-seven subjects were recruited from laparoscopic adjustable gastric banding or exercise and diet-weight loss programs. The dGEMRIC index was assessed on MRI according to established protocol. Regression analysis adjusted for age, sex, body mass index (BMI), and presence of clinical knee OA.Results.Mean age and BMI were 51 ± 12.7 years and 39.6 ± 6.2 kg/m2. Twenty-three subjects (30%) had clinical knee OA (American College of Rheumatology criteria). The medial and lateral dGEMRIC indices were 538 ± 80 ms and 539 ± 86 ms. Age correlated negatively with medial (r = −0.40, p < 0.001) and lateral (r = −0.29, p = 0.012) dGEMRIC index. Subjects with clinical knee OA had significantly lower medial dGEMRIC index; however, no association was found for BMI. Varus alignment correlated with lower medial dGEMRIC index (r = −0.43, p < 0.006), while quadriceps strength correlated positively with lateral dGEMRIC index (r = 0.32, p = 0.008). There was also a negative correlation between serum leptin and lateral dGEMRIC index in women (r = −0.39, p = 0.035), with a trend in men (r = −0.52, p = 0.08). There were weak associations with physical disability, as self-reported on the WOMAC questionnaire.Conclusion.In obese subjects, knee dGEMRIC index was associated with age, clinical knee OA, abnormal tibiofemoral alignment, and quadriceps strength. Longitudinal studies are required to assess the potential for improvement in dGEMRIC index with interventions such as strength training.