Physiological knee valgus exists in children between 2 and 8 years of age, with maximum knee valgus occurring between 2 and 4 years of age. By the age of 8 years the lower limb force line is barely altered and the force line returns to neutral. A variety of conditions can cause abnormal skeletal growth and development, resulting in a knee valgus deformity. Common disorders include: abnormal bone development (e.g. epiphyseal dysplasia); metabolic disorders (e.g. rickets, renal osteodystrophy); post-traumatic deformities; post-infectious deformities; localised fibrocartilage dysplasia; excessive obesity, overweight; osteoarthritis of the knee; rheumatoid arthritis.