Known scientifically as genu valgum, knock-knees is a condition in which the lower legs are angled outward. When a person with a severe case stands with his or her legs fully straightened, the knees will touch, but the ankles will not. A similar condition, known as bowlegs, occurs when the knees angle outward, such that they do not touch when a person stands with his or her feet together.
Both bowlegs and knock-knees are a normal part of child development. Typically, children will appear slightly bowlegged during the first three years of life. Around age two or three, the knees will angle inward as the child learns to walk properly. The knees generally straighten out by age five or six when a child develops normally.
In some cases, however, knock-knees may worsen or persist into late childhood. Overweight children are at a particularly high risk for this problem, as their legs may turn inward in an attempt to support the extra weight. In addition, diseases such as rickets or osteomyelitis can weaken the bones and contribute to the condition.
In other cases, knock-knees may develop due to an injury to the growth area of the shinbone, although this typically results in only one knocked knee. When it develops with no known cause, it's known as idiopathic genu valgum.
Untreated, persistent knock-knees can be very damaging to an individual's self-esteem during late childhood and adolescence. Adults who have this condition are also more susceptible to injury and chronic knee problems. Many individuals develop osteoarthritis, a painful condition caused by the uneven wearing of cartilage inside the joints. In very severe cases, it may also make it difficult for a person to walk.
Luckily, knock-knees can easily be corrected, particularly when they are detected early. Healthcare providers typically prescribe appliances such as night braces for children who have a family history of the condition. Orthopedic shoes may also be effective.
If the appliances fail to correct the problem, surgery may be recommended. For children, corrective procedures are most effective around the age of 10 or 11. Iif knock-knees go untreated and persist into adulthood, however, total knee replacement surgery may be necessary to relieve pain caused by the condition.