In bow legs the knees do not touch when standing or walking ('bandy').
In bow legs the knees are more widely apart than the rest of the leg. It is common in small children, who simply grow out of it, but in some people the bowing continues into adulthood.
Bowing may develop later in life, as arthritis breaks down the inner (medial) aspect of the knee joint, often due to a meniscus having been removed some years earlier ('medial compartment' arthritis). In countries where diet and health may be poor, bow legs may also occur from such things as scurvy.