Physical fitness
Physical fitness is related integrally to the development of knee problems. The same activity such as climbing stairs may cause pain from patellofemoral compression for someone who is physically unfit, but not for someone else (or even for that person at a different time). Obesity is another major contributor to knee pain. For instance, a 30-year-old woman who weighed 120lb at age 18 years, before her three pregnancies, and now weighs 285lb, had added 660lb of force across her patellofemoral joint with each step.