Excess weight puts a strain on every part of your body, including your ankles. Having to bear additional weight puts stress on bones, tendons and ligaments. Because your feet and ankles bear most of the burden of holding you up, they, along with knees and hips, might show signs of stress more frequently than nonweight-bearing joints. Several types of ankle damage can occur when your joints have to carry extra weight.
As little as a 10-lb. weight gain can increase mechanical stress on your ankle, the foot and Ankle Center of Washington reports. Extra weight might weaken tendons and ligaments, making sprains and strains more likely. Obesity also affects your gait and can lead to additional falls. A University of Oklahoma Health Sciences Center study published in the February 2008 issue of “Dynamic Medicine” found that obese older adults experienced more falls, 27 percent compared with 15 percent for normal-weight adults, as well as more stumbling episodes, 32 percent compared with 14 percent. Obesity also increases mechanical force on the joints, which can lead to osteoarthritis.
Being overweight not only increases your risk of falling and spraining your ankle, but also can lead to chronic ankle instability, even after healing. Obese adolescent athletes have three times the risk of sustaining a sprained ankle over nonobese athletes, reports Dr. Arya Sharma, obesity specialist at the University of Alberta. A study conducted by the Cincinnati Children's Hospital Medical Center and reported in the January 2005 issue of “Archives of Pediatric and Adolescent Medicine” found that obese children who suffered an ankle sprain had a 70 percent increase in chronic pain, swelling or re-injury after an ankle sprain six months after the original injury.
While sheer mechanical force of extra weight on ankle joints can increase the risk of osteoarthritis, inflammatory substances in adipose tissue also appear to increase damage to joints, researchers from Jefferson University report in the June 2007 issue of “Seminars in Arthroplasty.” Joints that become too damaged need artificial replacement.
Posterior Tibial Tendinitis
Posterior tibial tendinitis occurs when the tendon that connects the calf muscles to the navicular bone in the foot stretches and becomes inflamed and swollen. Obesity increases the risk of developing tibial tendinitis, which causes pain in the ankle and over-pronation, a rolling of the foot inward when you walk, or flatfoot. Immobilization, specially-made orthotics or anti-inflammatory medications might help heal posterior tibial tendinitis, although you might need surgery.