Bow legged refers to a leg shape in which the knees stay apart while the ankles touch when you stand upright with your feet together. Doctors call this genu varum, a varus deformity that loads the inside of the knee and the outside of the ankle unevenly. Children under about 18 to 24 months often look bow legged as their legs develop, and that pattern usually straightens on its own.
When the curve persists past early childhood, worsens, or appears uneven between the two legs, it can signal a condition worth evaluating, because chronic misalignment stresses the inner knee joint and can speed up cartilage wear over time.
This guide explains what the alignment actually looks like, why mild bowing is normal in toddlers, which causes deserve follow-up, and how correction options differ between kids and adults.
The Everyday Picture and the Medical Name
Stand in front of a mirror with your feet together and your legs straight. If a gap opens between your knees while your ankles touch, your leg shape fits the bow legged pattern. The size of that knee gap, called the intercondylar distance, is how clinicians grade severity during a physical exam. A small gap of an inch or two often falls inside normal variation, while a wider gap, especially past age two, raises the need for a closer look.
The medical term genu varum comes from Latin roots that describe the knee (genu) angling away from the body’s midline (varum). Doctors use the term because it pinpoints the joint that drives the shape, rather than just describing a look. Varus deformities can affect the knee, the hip, or the elbow, but bow legs always center on the knee.
It helps to know the opposite alignment, genu valgum, so the two do not get confused. Genu valgum, often called knock-knees, is the mirror image: knees touch or overlap while the ankles sit apart when standing. Most children briefly pass through a knock-knee stage between ages three and five before their legs settle toward a neutral adult alignment. Knowing which direction your knees angle is the first step in reading any picture or X-ray correctly.
Why Bowing Is Normal in Babies and Toddlers
Most newborns look bow legged because of how they were folded in the womb. As your baby begins to pull up, cruise, and walk, the femur and tibia rotate into a straighter position. That early phase of natural curving is called physiological genu varum, and it is a normal stage of growth, not a deformity.
Because this stage is so common, pediatricians track the curve against an age-based timeline rather than reacting to the shape itself. A symmetric, mild curve that is gradually improving in a child under about 18 to 24 months almost never signals a problem. By age three, most children show legs that look closer to straight when they stand, and by ages five to seven the alignment usually sits near neutral.
| Age | Typical Leg Appearance | Reason It Looks This Way |
|---|---|---|
| Birth to ~18 months | Visible bowing, feet together | Womb positioning, curled femur and tibia |
| ~18 to 36 months | Gradual straightening | Standing and walking rotate bones outward |
| ~3 to 5 years | Mild knock-knee (genu valgum) | Continuing bone rotation past neutral |
| ~6 to 7 years onward | Neutral adult alignment | Stable joint angles, finished growth plate rotation |
One parent-friendly way to think about it: the legs are not broken or stuck, they are simply passing through a stage. The red flags are not the curve itself, but whether the curve is staying the same, getting worse, or appearing on only one side after age two.
Because most childhood bowing quietly resolves on its own, the warning signs become easier to spot once you know what to measure.
The Causes That Actually Require Attention
A handful of conditions push the knee into a persistent bow shape beyond the normal developmental window. Each one acts on a different part of the leg, and the age at which it appears is often the strongest clue.
Blount’s Disease
Growth plate damage just below the knee on the inner shin defines Blount’s disease, a condition that warps the lower leg as a child grows. When that growth plate slows down on one side while the outer side keeps growing, the tibia angles inward and the knee gap opens. It usually shows up between ages two and four, often in children who started walking early or carry higher body weight.
Early stages can respond to bracing, while more advanced cases may need guided growth surgery to redirect the growth plate.
Nutritional Rickets and Osteomalacia
Children with rickets and adults with osteomalacia develop soft, weakened bones because their bodies cannot properly deposit calcium and phosphorus. Vitamin D plays a central role in that process, so a child with limited sun exposure, dark skin, exclusive breast-feeding without supplementation, or a diet low in calcium can develop soft, bowing bones under the body’s own weight. Rickets-related bowing tends to affect both legs and is often accompanied by delayed sitting, crawling, or tooth eruption.
Restoring vitamin D and calcium intake, under medical guidance, helps the bones regain strength, and orthopedic care addresses any residual angulation.
Genetic and Congenital Bowing
Some children are born with a tibial bowing that does not match the typical physiological pattern. Congenital bowing tends to be visible at birth and may be one-sided, and certain skeletal dysplasias, inherited conditions affecting bone growth, produce a persistent curve that does not resolve on its own. These cases often show up alongside a shorter limb, a foot positioned inward, or a family history of similar alignment.
Adult-Onset Bowing
In adults, the most common driver is progressive osteoarthritis. As cartilage on the inner knee thins, the joint tilts inward and the leg drifts back into a varus position, the same direction it angled during childhood. Once the cartilage loss is well established, exercise and shoe inserts cannot reverse the bony alignment, though they can ease pain and slow further wear.
| Cause | Typical Age of Onset | Usual Pattern |
|---|---|---|
| Blount’s disease | 2 to 4 years | Often one-sided, progressive |
| Nutritional rickets | Infancy to early childhood | Two-sided, with bone pain or delay |
| Congenital tibial bowing | Birth | Visible early, often asymmetric |
| Adult osteoarthritis | 50+ | Two-sided, gradual worsening |
An At-Home Visual Self-Check Anyone Can Do
Before booking an appointment, a simple three-step check takes about two minutes and gives you a clearer picture of what you are seeing. None of this is a substitute for a clinical exam, but it removes guesswork from the first conversation with a doctor.
- Stand with feet together. Let the ankles touch naturally. Look at the space between the knees and note whether both knees curve outward by the same amount.
- Walk across the room. Watch how the feet land. A foot that points outward, a hip that drops, or a limp that favors one side can all signal asymmetry.
- Estimate the knee gap. Use your own hand width as a rough ruler. A gap of one to two finger-widths in a toddler usually sits inside normal range; anything past three to four finger-widths, especially in an older child or adult, deserves a closer look.
Red flags that push this from a watch-and-wait moment to a prompt visit include a curve that is getting worse after age two, a curve that affects only one leg, knee or shin pain during normal walking, a sudden change in gait, or a child who seems to tire quickly compared with peers.
Spotting those red flags at home is useful only if you also know which ones actually warrant a clinical visit.
When Bowed Legs Need a Doctor and What Happens Next
The clearest thresholds for medical evaluation are tied to age, not to looks alone. Use these reference lines when deciding whether to book.
- Under 18 months: Mild, symmetric bowing that is improving on its own rarely needs imaging.
- 18 months to 3 years: Worsening curve, one-sided curve, or a limp calls for a pediatric orthopedic visit.
- 3 to 7 years: Any persistent curve, or new pain around the knee or shin, warrants a standing X-ray.
- Adolescence: A curve that is progressing, painful, or limiting sports deserves an orthopedic evaluation rather than watchful waiting.
- Adulthood: New bowing, or a long-standing one that is starting to hurt, is worth raising with a primary care doctor or orthopedist.
At the visit, the orthopedic exam is mostly visual and hands-on. The clinician watches the child or adult stand and walk, measures the intercondylar distance in finger widths or centimeters, and checks leg length. A standing X-ray, taken with both legs straight and the patella facing forward, gives the most useful measurement.
The hip-knee-ankle angle on that X-ray is the standard way to grade how far the tibia has angled inward, and it sets the baseline for any decision on treatment.
That grading scale directly shapes which correction options sit on the table next.
Bring the shoes your child wears most often to the appointment. Uneven wear on the sole is a quick visual cue that gait and alignment are pulling the foot in a specific direction.
Realistic Correction Options for Kids and Adults
What actually changes the leg shape depends almost entirely on whether the growth plates are still open. That single fact shapes the entire menu of correction options.
Children and Teens With Open Growth Plates
Because the bones are still growing, doctors can guide that growth rather than cut into the bone. Bracing is the most common starting point for Blount’s disease caught early and for some rickets-related curves, with custom knee-ankle-foot orthoses worn during the day or at night depending on the protocol.
Guided growth surgery, also called hemi-epiphysiodesis, places a small plate or staple on one side of the growth plate to slow growth on the curved side while the other side keeps growing, gradually straightening the leg over several months.
Adults With Closed Growth Plates
Once the growth plates fuse, usually in the mid to late teens, bones no longer respond to guided growth. Exercise can strengthen the hip and thigh muscles that support the knee, and shoe inserts can shift pressure off the inner joint, but neither one resets the bony angle. When pain, joint damage, or functional limitation reaches a point where daily life is affected, a corrective osteotomy becomes the option that actually changes alignment.
In an osteotomy, the surgeon cuts the tibia (sometimes the femur), removes a wedge, and fixes the bone with a plate so it heals in a straighter position. Recovery usually means several weeks on crutches, then a graded return to weight-bearing over two to three months, with full recovery often taking six months or longer.
| Approach | Best Fit | What It Actually Does |
|---|---|---|
| Watchful waiting | Mild physiological bowing under age 2 | Allows natural rotation to complete |
| Bracing | Early Blount’s disease, some rickets cases | Holds the knee in a straighter position while bones grow |
| Guided growth surgery | Children with open growth plates and progressing curve | Redirects growth so the leg straightens over months |
| Corrective osteotomy | Adults with painful, established varus | Realigns the bone with a surgical cut and plate |
A practical way to use this table: start with watchful waiting if your child is under two and the curve is mild and symmetric, move to a pediatric orthopedic visit if the curve worsens or feels uneven, treat bracing as a serious early-stage option rather than a fallback, and think of osteotomy as a real but careful decision reserved for adult cases where pain or function has crossed a clear threshold.
The Big Picture
Bow legged is a description, not a diagnosis. Most children pass through a mild, symmetric bow shape on the way to a normal adult alignment, and the curve usually straightens on its own by age three.
Persistent, worsening, or one-sided bowing, especially when paired with pain or a limp, is the signal to involve an orthopedic specialist who can grade the angle on a standing X-ray and decide whether bracing, guided growth, or corrective osteotomy is worth the trade-offs.
FAQ
What does bow legged mean in medical terms?
In medical language, bow legged is called genu varum. It describes a varus deformity at the knee where the knees angle outward while the ankles stay together when standing, the opposite of genu valgum, or knock-knees.
Is being bow legged a problem?
Mild bowing is normal in infants and toddlers and usually resolves by about age three without treatment. Persistent bowing past early childhood can increase wear on the inner knee and outer ankle, sometimes leading to pain, gait changes, and earlier osteoarthritis.
What causes someone to be bow legged?
Common causes include normal physiological bowing in young children, Blount’s disease (a growth plate disorder of the tibia), nutritional rickets from low vitamin D and calcium, congenital tibial bowing, and adult-onset osteoarthritis that tilts the knee inward as cartilage wears down.
Can bow legs be corrected in adults?
Exercise, shoe inserts, and physical therapy can ease symptoms but do not change the bony angle in adults. Corrective osteotomy surgery is the option that realigns the bone and is typically reserved for cases with significant pain, deformity, or early joint damage.
When should a parent be concerned about bow legs in a child?
Concern is warranted when the curve is getting worse after age two, affects only one leg, comes with pain or a limp, or sits alongside delayed motor milestones. A pediatric orthopedic evaluation with a standing X-ray is the standard next step.
Do bow legs get worse with age?
Physiological bowing usually improves with age. Bowing driven by Blount’s disease, untreated rickets, or significant genetic conditions tends to worsen until the underlying cause is treated, while adult bowing caused by osteoarthritis often progresses as cartilage continues to wear.
