Bow legged means your legs curve outward at the knees, creating a gap between them even when your ankles are together. The medical term is genu varum. If you looked at someone with bow legs from the front, their legs would form the shape of a parenthesis or a bow, which is where the name comes from. In most cases, bow legs are a completely normal part of early childhood development, but in older children and adults, the condition can signal an underlying problem that needs attention.
Why Almost All Babies Are Bow Legged
Babies are born with bowed legs because of the cramped, curled position they held in the womb for months. This is called physiological genu varum, and it’s not a disorder. It’s simply the starting point for leg development. As a baby begins to stand and walk, typically between 11 and 18 months, the legs gradually straighten. Most children grow out of bowing entirely by age 2.
After the legs straighten, many toddlers actually swing the other direction for a while, becoming slightly knock-kneed (knees angling inward). This also corrects on its own. By around age 7 or 8, the legs settle into their adult alignment. The entire process is driven by normal bone growth and weight-bearing, and it rarely needs any intervention.
When Bowing in Children Is Not Normal
If a child’s legs are still noticeably bowed after age 2, or if the bowing gets worse instead of better, something else may be going on. Two conditions account for most pathological bowing in kids.
Blount’s disease is an abnormality of the growth plate at the top of the shinbone. It can appear in toddlers or adolescents and causes progressive bowing that worsens over time rather than resolving. In children under 2, it can be impossible to tell Blount’s disease apart from normal developmental bowing just by looking. By age 3, though, the difference becomes clear: the bowing worsens, and X-rays show characteristic changes at the top of the tibia. A standing X-ray is the standard way to confirm the diagnosis.
Rickets, caused by a severe deficiency of vitamin D, calcium, or phosphorus, softens growing bones and allows them to bend under the child’s weight. Rickets produces bowing along with other signs like delayed growth and widened wrists. It’s less common in developed countries but still occurs, especially in children with very limited sun exposure or restrictive diets.
What Causes Bow Legs in Adults
Adults don’t develop bow legs from the same growth-related causes that affect children. In adults, the most common driver is osteoarthritis of the inner (medial) compartment of the knee. As the cartilage on the inner side of the knee wears down, the joint space narrows unevenly, and the leg gradually angles outward into a bowed position. The bowing and the arthritis feed each other: the misalignment increases pressure on the inner knee, which accelerates cartilage loss, which worsens the misalignment.
Several factors raise the risk of this kind of wear. Obesity is one of the strongest, with risk climbing progressively as body weight increases. Previous knee injuries, particularly torn ligaments or meniscus tears that required surgical removal, significantly increase the odds of developing arthritis later. Occupations that involve prolonged squatting, kneeling, or climbing more than 10 flights of stairs per day also elevate risk. Less commonly, inflammatory conditions like rheumatoid arthritis or gout, and metabolic diseases like diabetes, can contribute to cartilage breakdown that leads to bowing.
Old fractures of the shinbone or the tibial plateau (the flat top of the shinbone that forms part of the knee joint) can also leave the leg in a bowed position if the bone heals with residual angulation.
How Bow Legs Are Measured
Doctors assess the severity of bowing with a full-length standing X-ray that captures both legs from hip to ankle. On this image, they draw lines from the center of the hip joint through the knee and down to the ankle to determine the mechanical axis of each leg. In a normally aligned leg, this line passes through or very near the center of the knee. When the line falls to the inner side of the knee, the leg is in varus alignment, which is the technical way of saying it’s bowed.
The degree of deviation tells the doctor how severe the bowing is and helps guide treatment decisions. For children, doctors also assess skeletal maturity to estimate how much growth remains, since this determines whether the bowing might still correct on its own.
Treatment for Children
Normal developmental bowing requires no treatment at all. The standard approach is observation, with periodic checkups to confirm the legs are straightening on schedule.
When bowing persists because of Blount’s disease or another pathological cause, a procedure called guided growth surgery can correct the alignment. The idea is straightforward: a small plate or screw is placed on one side of the growth plate near the knee, temporarily slowing growth on that side while the other side continues growing. Over months, this gradually straightens the leg. Correction rates are roughly 0.8 degrees per month in both the thighbone and shinbone. Once the leg reaches proper alignment, the hardware is removed and growth resumes normally.
Timing matters. If surgery is done too close to the end of a child’s growth period, there may not be enough growing time left to achieve full correction. If it’s done too early in a very young child, there’s a risk of overcorrecting into a knock-kneed position. Blount’s disease can be particularly challenging to treat: in some studies, hardware failure occurred in up to half of patients with Blount’s disease, and fair or poor outcomes were reported in roughly two-thirds of Blount’s cases treated with staples.
Treatment for Adults
For adults with bow legs caused by arthritis, initial management focuses on the arthritis itself: weight management, physical therapy to strengthen the muscles around the knee, and pain relief. Losing weight reduces the load on the inner knee compartment and can slow the cycle of damage.
When conservative measures aren’t enough, a surgical option called high tibial osteotomy can realign the leg. The surgeon cuts the shinbone near the knee and angles it slightly to shift weight-bearing stress away from the damaged inner compartment. This procedure works best for active patients under 50 who have arthritis limited to one compartment of the knee. It’s generally not recommended for patients with a BMI over 35, those who can’t bend their knee to at least 90 degrees, or those whose bowing exceeds about 10 degrees.
For older adults or those with more advanced arthritis, partial or total knee replacement may be a better option than osteotomy, since the goal shifts from preserving the joint to replacing the damaged surfaces entirely.
Signs That Bowing Needs Evaluation
In children, bowing that worsens after age 2, affects one leg more than the other, or causes a noticeable limp warrants an X-ray. Pain in the knees or shins in a bow-legged child is not typical of normal development and should be checked.
In adults, new or worsening bowing is almost always accompanied by knee pain, stiffness, or difficulty walking. A progressive change in leg shape, especially if one knee is more affected than the other, points to cartilage loss that can be confirmed with imaging. Early evaluation gives more options for slowing the process before the damage becomes severe.