Weight gain impacts joint pressure because extra weight causes stress on the joints of the lower body, especially the knees. In fact, with every extra pound (0.45 kg) of additional body weight, 4 pounds (1.81 kg) of pressure is added to the knees, the joints that are responsible for carrying the most body weight. More than half of all people who suffer from arthritis, a disease that causes joint inflammation, are obese. Weight gain might especially affect the joint pressure in children because the stress on the joints could damage the cartilage at the end of bones while they are still growing.
More about the impact of weight:
Excess weight accounted for 3% of all cases of joint inflammation in 1971 — and had risen to 18% by 2002.
About one-third of the children and young adults in the US are considered to be overweight or obese, according to 2014 statistics, and they are about five times more likely to be obese as adults.
A weight loss of 11 pounds (5 kg) could reduce the likelihood of arthritis in the knees by 50%.