How Does the Knee Structure Change Across a Lifespan?

As a person ages, the knee muscles, tendons and joints undergo changes that make them more susceptible to damage and painful conditions, states Everyday Health. This is due to years of wear and tear on the knees, and the issues can be worse in people who are overweight, those with previous injuries to the knee and those suffering from certain chronic illnesses, reports the Rubin Institute for Advanced Orthopedics.

Scientists have found that people older than 65 commonly experience knee pain, according to Everyday Health. In most cases, this is due to osteoarthritis, a condition in which the protective cartilage in the knee breaks down. Additionally, muscles shrink in size as much as 40 percent throughout adulthood. This loss of strength in the leg and hip muscles leads to diminished support of the knees, allowing damage from weight-bearing activity to cumulate.

Another age-related change that occurs most frequently in older women is osteonecrosis, a condition in which a portion of the knee bone loses its blood supply, dies and ultimately collapses, explains the Rubin Institute for Advanced Orthopedics. The cause of this condition is unknown, though some doctors believe it may be due to trauma or pressure from fluid build-up resulting in restricted blood flow.