What Causes Bow Legs in Adults, and Can They Be Straightened?
Bow legs (genu varum) in adults are usually caused by gradual cartilage wear on the inner side of the knee, previous injury, or a childhood condition that was never fully corrected. The outward curve shifts extra load through the inner knee, which can speed up arthritis. A standing, weight-bearing scan of the full leg shows the true degree of misalignment and helps guide whether bracing, physiotherapy or surgery is right for you.
Key takeaways
- Bow legs in adults are called genu varum. They create uneven load across the knee joint.
- The most common adult cause is wear-and-tear arthritis on the inner (medial) side of the knee.
- Pain often appears at the knee, but the root cause can sit higher or lower in the leg alignment chain.
- A full-leg standing x-ray reveals alignment that lying-down scans can miss.
- Treatment ranges from exercise and bracing to surgical realignment, depending on severity.
What are bow legs in adults?
Bow legs, known medically as genu varum, describes a posture where your knees stay apart even when your ankles are together. In a well-aligned leg, a straight line from your hip through the centre of the knee hits roughly the middle of the ankle. When you are bow legged, that line falls to the inner side of the knee instead, concentrating force through the medial compartment of the joint.
A small degree of outward curve can be normal and cause no trouble at all. Problems start when the angle is large enough to overload one side of the knee, wearing down cartilage faster than it can repair itself. Over time, this uneven load may progress to osteoarthritis, stiffness, and pain that limits walking.
How do you know if you are bow legged?
Many people live with mild bow legs and never notice them. The signs below suggest the alignment may be significant enough to investigate further.
When you stand with your ankles touching, a clear space remains between your knees.
Aching or stiffness on the inner side of one or both knees, especially after walking or standing.
The outer edges of your shoe soles wear down faster than the inner edges.
A rolling or wide-based walking pattern that feels less stable over longer distances.
What causes bow legs in adults?
In most adults, bow legs develop gradually rather than appearing overnight. The main causes include the following.
Cartilage on the inner knee wears down, narrowing the joint space and tilting the shin outward.
A shinbone or thighbone fracture that healed at a slight angle can leave lasting varus alignment.
Conditions such as Blount's disease or rickets that were not fully treated in childhood can persist into adulthood.
Paget's disease, vitamin D deficiency, or other metabolic bone disorders can soften bone and allow gradual bowing.
Because the body works as a connected chain from feet to head, a varus tilt at the knee rarely stays isolated. The hip, pelvis, and lower back often compensate to keep you balanced. That is why people with bow legs sometimes feel pain in their hip or lower back rather than at the knee itself.
Why does a standing scan show bow legs more accurately?
A standing, weight-bearing image captures your legs under the same forces they experience every day. Lying down for a standard x-ray or MRI relaxes your muscles and removes gravity, so the true curve of the leg is partially hidden. This means the degree of misalignment can look smaller than it really is.
A full-leg standing image captures the hip, knee and ankle in one single exposure while you bear your full body weight. The mechanical axis of each leg is measured from hip centre to ankle centre, showing exactly where force passes through the knee. This is the gold standard for planning any alignment correction.
ScanAlign standing EOS imaging uses about 90% less radiation than a standard x-ray, around ten times less. You simply stand still for a few seconds while the scanner moves from head to foot.
A standard x-ray or CT taken while lying down removes gravity and relaxes soft tissue. The knee may appear better aligned than it truly is when you walk. Lying-down images also tend to capture only part of the leg, so the overall mechanical axis cannot be measured reliably.
When is MRI the better option? EOS shows bones, joints and alignment clearly. If your consultant suspects soft-tissue damage, a torn meniscus, ligament injury, or nerve involvement, MRI is usually the better tool for those structures. The two scans complement each other.
Can bow legs in adults be corrected?
Yes, in many cases. The right approach depends on how much the alignment has shifted and how much it affects your daily life. ScanAlign is a diagnostic imaging clinic, not a treatment provider. Our role is to give you and your clinician a clear, full-leg standing image so the best path forward can be chosen with confidence.
The options your consultant may discuss generally fall into a few categories.
Strengthening the muscles around the knee and hip to improve support and reduce uneven loading.
A specially designed brace that shifts pressure away from the worn inner compartment.
A surgical procedure that reshapes the shinbone or thighbone to realign the leg. Often considered for younger, active patients.
A partial or total knee replacement may be recommended when arthritis is advanced and other options have been exhausted.
Accurate alignment data from a full-leg scan is particularly important before osteotomy or replacement surgery. The surgeon needs to know the exact mechanical axis to plan the correction precisely. Read more about bow legs and knock knees on a standing scan and the difference it makes to surgical planning.
Bow legs are the mirror image of knock knees, where the knees angle inward instead. Both conditions benefit from the same type of full-leg standing assessment.
Want to understand your alignment before deciding on next steps? You can book a full-leg alignment scan or start with a free video consultation to discuss whether imaging is right for you.
Book a free video consultationFrequently asked questions about bow legs
The most common cause is osteoarthritis wearing down the cartilage on the inner side of the knee. Previous fractures, childhood conditions such as Blount's disease, and metabolic bone disorders like vitamin D deficiency can also lead to bowing.
Yes. When the mechanical axis is shifted, extra load passes through the inner knee. This accelerates cartilage wear, which in turn increases the bowing further. Early assessment can help monitor progression.
They can. The uneven distribution of force through the knee joint often leads to pain, stiffness and swelling on the inner side. Some people also experience hip or lower-back discomfort as the body compensates.
Bow legs (genu varum) curve outward so the knees stay apart. Knock knees (genu valgum) angle inward so the knees touch while the ankles stay apart. Both are forms of varus or valgus malalignment and benefit from the same standing full-leg assessment.
Exercise alone cannot change bone shape, but targeted strengthening of the hip and thigh muscles can reduce the abnormal load on the knee and ease symptoms. Your physiotherapist or consultant can advise a programme based on your alignment data.
An osteotomy is a surgical procedure where a wedge of bone is removed or added to the shinbone (or occasionally the thighbone) to realign the leg. It is most commonly considered for younger, active adults whose arthritis is limited to one compartment.
Standing adds gravity and your body weight, which reveals the true degree of bowing under everyday conditions. Lying-down images relax the muscles and can make the alignment look better than it really is.
EOS uses about 90% less radiation than a standard x-ray, around ten times less. It is a quick, comfortable scan where you simply stand still for a few seconds.
No. ScanAlign accepts self-referrals. You can book a free video consultation first, and the clinical team will confirm whether a scan is appropriate for you.
Pricing details are available on the ScanAlign website. Start with a free video consultation to discuss your needs and receive clear information about costs before committing.
See your alignment clearly
A full-leg standing scan shows the mechanical axis of each leg under real weight-bearing conditions. Start with a free consultation to find out if imaging is right for you.
Book a free video consultationSources
- Brouwer, G.M. et al. "Association between valgus and varus alignment and the development and progression of radiographic osteoarthritis of the knee." Arthritis & Rheumatism, 2007; 56(4): 1204-1211.
- NHS. "Osteoarthritis: treatment and management." NHS website, accessed 2024.
- Paley, D. "Principles of Deformity Correction." Springer, 2002. Standard orthopaedic reference on limb alignment and osteotomy planning.
Written by Abbas Dhami (Specialist Diagnostic Radiographer)
This page is general information and not a diagnosis.
ScanAlign is the trading name of CoreMed Solutions Ltd and operates under The Harley Street Hospital's CQC licence.