Obesity is a complex multifactorial chronic disease resulting from the interaction of genetic and environmental factors. On the pathophysiology of obesity, social, behavioral, cultural, metabolic and neuroendocrine factors emerge that have not yet been fully studied (1). The rapid and continuous increase in the prevalence of obesity observed in recent years has led the World Health Organization to define this pathology as a “globesity” global epidemic (2). In the United States, 32% of adults are overweight and 22.5% are obese (3). Very similar or higher values are found in Europe (4). In Italy 9% of adults are obese and 33.5% are overweight (5). Prevalence is highest in middle age, in southern areas and among individuals with low income and low cultural level (6,7,).
The prevalence of obese in developmental age varies between 10 and 30% (8); Obesity in this period of life is a risk factor for obesity in adulthood. (9) Obesity is excessive accumulation of body fat, frequently resulting from a sustained positive energy balance. The excess fat mass appears to consist of hypertrophy and hyperplasia of the adipocytes (10). At the individual level, the assessment of the characteristics of obesity requires the analysis of the body composition which can be detected with various techniques; to allow the setting of personalized therapeutic protocols at the population level it is sufficient to resort to simple, easily measurable indicators.
The Body Mass Index (BMI) or Body Mass Index (BMI), calculated as the ratio between the weight in kg and the square of the height in m2, proposed by international institutions or organizations (2), it is correlated with the percentage of fat mass and associated with the incidence of various diseases and mortality (11). The classification of weight states (WHO, 1998) includes the following categories: underweight: BMI <18.5 Kg / m2 normal weight: BMI 18.5-24.9 Kg / m 2 overweight: BMI 25-29.9 Kg / m 2 obesity: BMI> 30 Kg / m 2 great obesity: BMI> 40 / m 2Regional distribution of body fat, which cannot be measured by BMI alone, is more important to health than total fat (12, 13). Intra-abdominal or visceral deposition of fat is associated with complications, particularly cardiovascular disease.
It is much more accurate then to consider both BMI and waist circumference (14). Excessive amounts of body fat constitute a health hazard, both for the risk of onset of metabolic diseases and for the mechanical consequences caused by the overload on the joints (15). The joint balance is negatively affected by an excessive and lasting load. Osteoarthritis can be considered the result of an imbalance between the amount of work required by the joints and the capacity to work sustainable by these (16).
This decompensation can be the consequence of an inability on the part of the joint structures to withstand normal stresses or a continuous overload of normal structures. These mechanisms involved in various percentages in the primary and secondary forms are at the basis of the degenerative alterations of the arthrosic process (16). The onset of joint pathology manifests itself as a subversion of the cartilage structure, to which the chondrocytes react with the production of an incorrectly structured fundamental substance.
The result is an inflammatory and degenerative pathology which, involving the other joint components (epiphyseal bone below the cartilage, synovial membrane, capsule-ligamentous structures), leads to osteoarthritis. Knee localization is the most frequent and one of the most disabling (17). The association of obesity and osteoarthritis of the knee is well documented. 17.8% of Italians suffer from it. The female sex is most affected. In addition to overweight and obesity, other risk factors such as ligament laxity, axial defects (varus or valgus knee) and a sedentary lifestyle predispose to the onset of osteoarticular pathology.
An important signal is pain, absent at rest and present in standing or walking. Progressively, the joint becomes more and more limited in movement, inducing a sedentary lifestyle, preventing daily activities and worsening the quality of life. In children, obesity causes damage to the skeletal growth nuclei, onset of muscle aches and posture changes involving knees and feet. This is predictive of osteoarthritis that will manifest itself in the adult. It is important to promote a gradual reduction in body weight in every obese patient to prevent disability, just as in the non-obese arthritic subject it is important to avoid excessive weight gain which would cause an aggravation and evolution of the morbid process (18). The treatment of obesity is essential for the functioning of the osteo-articular system, even in the absence of pain. The joint is progressively negatively affected by excessive load and a balanced low-calorie diet, according to the guidelines, is often sufficient to restore the lost balance.
It is important to underline that overweight or obesity can sometimes be secondary to a pre-existing arthritic condition which, due to pain and functional limitation, leads to a sedentary lifestyle. Also in these cases it is necessary to adopt adequate dietary therapy in association with the most suitable treatments (19). The therapy against obesity aims to reduce body weight in the order of 10% compared to the initial one. This result significantly reduces the severity of associated risk factors, can be achieved within six months and can be maintained over time. A balanced diet aimed at causing a calorie deficit of 500/1000 Kcal / day, compared to the patient’s consumption, such as to cause a weight reduction not exceeding 1 kg per week, it should be an essential component of the obesity treatment strategy.
The combination of a low-calorie diet, increased physical activity and behavioral therapy is the most successful therapy for weight loss and maintenance. For carefully selected subjects with morbid obesity (BMI> 40) or with BMI> 35 and concomitant pathologies, when less invasive methods have proved ineffective, a possible strategy is bariatric surgery (20). The combination of weight loss and moderate exercise is significantly more effective than either intervention alone or better lifestyle counseling in reducing pain and improving function in patients with knee osteoarthritis
