Reviewed by Coach Dr. Diksha (PT) Orthopedic & Medical Fitness Expert at ThriveCore | Last updated: October 2026
Ever looked in the mirror and wondered about your leg alignment? When your ankles touch, do your knees stick out? Or when your knees touch, do your ankles stick out?
The bow legs are differentiated from knock knees by the curvature of your leg. Known medically as genu varum and genu valgum, these conditions show opposite types of knee alignment. Dealing with bow legs or knock knees as adults can bring up questions about an abnormal knee alignment.
If you want to know how to tell if you have bow legs or knock knees, this guide is for you. We’ll compare the causes and symptoms of bow legs vs knock knees, and when you’d need more than exercise.
But if you want a deeper look at bow leg causes and exercises specifically, our full guide on how to correct bow legs in adults covers them in detail.
What’s the Difference Between Bow Legs and Knock Knees?
Bow legs and knock knees are opposite lower limb alignments. They’re usually a normal part of growth in infants and children.
According to the American Academy of Orthopaedic Surgeons, bowing is normal in children under about 2 and usually straightens by age 3 to 4.
The Pediatric Orthopaedic Society of North America (POSNA) says that knock knees may often appear around age 3 or 4 and usually straighten by age 7 to 10.
| Feature | Bow Legs (Genu Varum) | Knock Knees (Genu Valgum) |
| Appearance | Knees are apart, ankles touch | Knees touch, ankles are apart |
| Normal Age Range | Common and normal from birth up to 18 to 24 months | Common and normal developmental peak around ages 3 to 5 |
| Natural Resolution | Usually straightens out by age 2 as the child walks and bears weight | Usually straightens out into normal adult alignment by ages 7 to 11 |
| Weight Load Area | Concentrates stress on the inner knee compartment | Concentrates stress on the outer knee compartment |
| Underlying Pathologies | Can be linked to rickets (vitamin D deficiency) or Blount’s disease if persistent | Can be linked to obesity, rickets, or previous lower limb injuries |
How Do I Know If I Have Bow Legs or Knock Knees?
You can identify bow legs or knock knees by checking the position of your knees. See if your knees and ankles align when you stand up straight with your feet together.
The NHS Greater Glasgow and Clyde (NHSGGC) guidelines explain that you can check a child’s leg shape by looking at the spaces between their joints.
But for adults, here’s a simple way to check:
- Stand straight in front of a mirror, bare feet, with your ankles together.
- Check if, when your ankles touch, your knees curve outward with a wide gap between them. If they do, then that’s bow legs.
- If your knees touch but your ankles are spread wide apart and can’t meet, that’s knock knees.
- Check your kneecaps to see if they face straight ahead or twist inward or outward.
This bow legs and knock knees self check is only a rough visual guide, not a diagnosis.
For a proper diagnosis, an orthopedist would need to do a medical examination including gait analysis, angle measurement (such as the Q-angle, which reflects how the thigh muscle pulls on the kneecap) and even X-rays.
What Causes Bow Legs or Knock Knees in Adults?
When adults have knock knees or bow legs, it is usually because their joints have worn down, they had a past injury or a bone disease changed the shape of their legs. These leg problems may either start when a person is older or stay from childhood.
Shared causes
- Osteoarthritis: Inner knee cartilage loss may result in bow legs. Outer knee loss leans towards knock knees.
- Excess weight: May add stress to the knees and speed up the wearing of cartilage, especially when your alignment is already off.
- Old injuries: Fractures that healed out of line, or growth plate damage may also cause these.
- Vitamin D or calcium deficiency: Severe, long term deficiency may soften bone (osteomalacia in adults) and can result in bow legs.
More specific to bow legs
- Blount’s disease: A shinbone growth disorder that may remain as an adult.
- Paget’s disease of bone: This condition weakens and deforms the bone.
- Inherited bone conditions: Such as skeletal dysplasias can cause these.
More specific to knock knees
- Rheumatoid arthritis: Inflammation may damage joint cartilage which may cause the knee to lose its structure.
- Flat feet: May be found along with knock knees. But it’s just associated with the condition, not a proven cause.
Note: Both shapes are normal in young children. Bow legs usually straighten by about age 2. Knock knees ease by early school age. See a pediatrician if a child’s legs look worse over time or uneven.
Do Bow Legs and Knock Knees Cause the Same Symptoms?
No, bow legs and knock knees do not always cause the exact same symptoms. But they share several mechanical and long term joint complications across the musculoskeletal system.
Symptoms that can show up with both:
- Knee pain or stiffness
- Gait and walking issues with a limp
- Your shoes wearing unevenly
- Hip, pelvis, ankle or lower back discomfort
- Your legs get tired after walking or standing
With bow legs (varus alignment), extra weight may squeeze the inner knee. With knock knees (valgus alignment), that heavy stress shifts to the outer knee.
A 2001 JAMA study by Dr. Leena Sharma proved these angles cause fast joint damage. Bow legs make inner knee damage 4 times more likely to worsen. While knock knees make outer knee damage 5 times more likely to worsen. Over time, this may make everyday movements like standing up from a chair much harder.
Can Alignment Exercises Correct Bow Legs or Knock Knees in Adults?
No, the alignment exercises cannot change the hard bone structure of bow legs or knock knees of adults. But strengthening exercises can improve muscle strength, joint stability and alignment around the hips and knees to reduce pain and manage symptoms.
According to the American Physical Therapy Association (APTA), exercise can:
- Help you build strength in your thigh, hip and calf muscles
- Improve your balance and joint stability
- Help you manage structural knee pain and daily function
- Reduce strain on your knee by helping to maintain a healthy weight
But even with all this exercise, the structural curve of the femur (thigh bone) or tibia (shin bone) remains the same and doesn’t change the bone alignment.
If you want a deeper look at bow leg causes and exercises specifically, our full guide on how to correct bow legs in adults covers them in detail
A physiotherapist can help design a strengthening plan around your pain and fitness level.
For severe, painful or functionally limiting deformities in adults, orthopedic specialists at HSS recommend surgical realignment procedures like an osteotomy are the only way to physically straighten the bone.
Do Bow Legs or Knock Knees Increase Arthritis Risk?
Yes, bow legs and knock knees can increase the risk of knee osteoarthritis or cause existing arthritis to get worse.
In the Multicenter Osteoarthritis Study (MOST), scientists tracked more than 2,200 people over several years. They discovered that:
- People who were bow legged but had completely healthy knees at the start were 1.5 times more likely to develop brand new knee arthritis than people with straight legs.
- If a person already had minor knee damage, uneven leg shape made it worse much faster.
- Bow legs multiplied the risk of ruining the inner side of the knee by 3.5 times. Knock knees multiplied the risk of ruining the outer side of the knee by nearly 5 times.
This study proved that crooked legs aren’t just about how you look. Since these conditions may change how your weight gets distributed onto your joints, they can destroy the protective cartilage over time.
To help you manage this better, an arthritis and joint pain fitness program can give you a safe, structured routine to strengthen the muscles around your knee, with guidance matched to your fitness level.
How Can I Check My Leg Alignment More Reliably Than Just Looking?
You can check leg alignment more reliably than just looking by using structured functional movement tests, standardized clinical checks or professional imaging like x-rays.
A study in the ESSKA journals had researchers take precise camera pictures of people’s legs under different conditions, testing how things like camera distance, foot width and leg rotation changed the results. It concluded that digital photos are a highly reliable and safe way to track leg alignment over time, but only if the patient stands perfectly still and exactly the same way for every photo.
It also works the same way with an AI posture screening test where it takes you through photos and points out alignment patterns.
But be sure to view these results as a starting point, not a diagnosis. It just helps you decide if you need to see an orthopedic specialist or physiotherapist in person.
Which Is More Common in Adults: Bow Legs or Knock Knees?
Bow legs are more common than knock knees in general and this is especially true in men. But the exact answer depends on the exact ages and underlying health problems.
- Regular young adults: The Korean Journal of Legal Medicine reports that bow legs are relatively common in healthy young adults with around 32% of men and 17% of women affected.
- Adults with obesity: Research in the ACTA Biomedica showed that knock knees become slightly more common for people with obesity, appearing in about 10% of this population compared to 8.6% for bow legs.
- Older adults with severe osteoarthritis: Knock knees are slightly more frequent here, making up 47-52% of advanced arthritic alignment deformities. And bow legs account for 35-47%, researchers in the Pakistan BioMedical Journal showed.
Ultimately, bow legs may be more common in healthy young adults, but factors like obesity and severe osteoarthritis shift the balance toward knock knees as the population ages.
Can You Have Bow Legs in One Leg and Knock Knees in the Other?
Yes, you can have one bow leg and a knock knee on the other leg. This is called windswept deformity. Both legs lean the same way, like trees bent by the wind.
It’s much less common than having the same pattern in both legs. It can have several causes, including childhood bone conditions such as rickets, past injury or uneven joint wear. Since the cause isn’t always clear, you would need to evaluated in person.
When Should You See a Doctor About Bow Legs or Knock Knees?
Adults should see a doctor about bow legs or knock knees when the alignment causes joint pain, stiffness, difficulty walking or climbing stairs. Also check it if the condition is progressively worsening.
Make sure to get checked soon if you see:
- Leg, knee or hip pain that persists during the day.
- Shaky, weak or wobbly knees.
- Early signs of arthritis such as swelling, grinding of bone or difficulty bending your legs.
- Uneven legs. One side appears to be much more curved than the other.
- Having a functional dissatisfaction that may affect confidence, mobility or ability to stay active.
If you experience any of these, make sure you get it evaluated by an orthopedic specialist. This information does not provide any diagnosis or treatment.
Frequently Asked Questions
Can bow legs turn into knock knees, or the other way around?
Yes, a child’s legs naturally transition from bow legs to knock knees and back to a straight alignment as part of normal growth.
Which is worse, bow legs or knock knees?
Neither bow legs nor knock knees is “worse” than the other, both are common stages of development in young children. They usually correct themselves as they grow. But in adults, both may strain the knees or cause other symptoms.
Can you have bow legs and knock knees at the same time?
Yes, you can have knock knees and bow legs at the same time. But usually one leg bends out and the other bends in, or the shape changes as you grow up.
Do bow legs or knock knees get worse with age if untreated?
Untreated bow legs and knock knees may worsen as you grow older. It’s mostly due to age related joint wear, cartilage breakdown and changing bone density.
Can losing weight correct bow legs or knock knees in adults?
No, you can’t lose weight to physically straighten or fix bow legs or knock knees in adults. But it may help ease strain on your joints.
Is surgery the only way to change bone alignment for either condition?
Yes, surgery is the only way to permanently change or realign the bone structure for adult bow legs (varus deformity) or knock knees (valgus deformity). But in children, the conditions usually get rectified by themselves.
Do flat feet cause knock knees, bow legs, or both?
Flat feet can cause knock knees but not bow legs. When your foot arches collapse, your ankles roll inward. This twists the bones in your legs, and pulls your knees in.
Can shoes or orthotics correct bow legs or knock knees in adults?
No, special shoes and orthotics won’t fix or correct the structure of bow legs or knock knees in adults but they may provide some help. A podiatrist can look at your feet, arches and shoes and recommend custom orthotics if needed.
Is knee pain always a sign of one of these conditions?
No, knee pain does not always mean you have knock knees or bow legs. Most knee pain may be caused by completely different things, like an everyday injury or working the muscle too hard.
Bow Legs or Knock Knees: What Should You Remember?
Bow legs and knock knees are both alignment changes but in opposite directions. Their causes and symptoms may overlap, but bow legs load the inner knee while knock knees load the outer knee.
In adults, exercise supports the muscles around the joint but doesn’t reshape bone. A mirror check is a starting point, not a diagnosis.
If you want a first look at your alignment, our free AI posture screening test can guide you. It will help give you a starting point for understanding your posture and provides useful information so you can get the help you need.