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Key Takeaways
- Valgus alignment causes knees to touch and can lead to knee osteoarthritis.
- Varus alignment causes knees to bow outward and increases the risk of knee osteoarthritis.
- Both valgus and varus knee issues often improve or correct naturally as children grow.
A perfectly positioned knee has its load-bearing axis on a line that runs down the middle of the leg, through the hip, knee, and ankle. When a congenital issue, trauma, or other condition interferes with this, valgus or varus misalignment can occur.
Valgus knee alignment, better known as knock knees, causes the knees to touch and the feet to be significantly apart when standing. With varus knee alignment, the knees don’t come together even when your feet are side by side. Both conditions put increased stress on the knees, which can lead to or worsen arthritis.
Learn about the differences between valgus and varus knee alignments, why they can occur, what they can cause, and how they are treated.
Illustration by Joules Garcia for Verywell Health
Characteristics of Valgus Alignment
Valgus misalignment occurs when the knees bend inward and either touch or “knock” against each other. This shifts the weight-bearing axis to the outer side, increasing stress on the lateral (outer) compartment of the knee.
A valgus knee condition results in being knock-kneed. Besides damaging the cartilage that covers bone surfaces and narrowing joint space, knee misalignment can affect the menisci, which are cartilage “cushions” between the bones.
The lateral meniscus is specifically affected in valgus misalignment.
Although not as destructive as varus alignment, valgus alignment is concerning because it can increase your risk of knee osteoarthritis and cause it to progress. It can be painful, and activities like walking or climbing stairs may be especially challenging.
Characteristics of Varus Alignment
Varus alignment shifts the weight-bearing axis of the leg inward, placing more stress on the medial (inner) compartment of the knee. This results in the knees bowing outward, hence the term “bow-legged.”
Being bow-legged increases your risk of developing knee osteoarthritis. This risk is much higher if you are overweight or obese, though losing weight may help reduce this risk.
The degree of varus alignment also affects your risk of knee osteoarthritis. Greater misalignment corresponds to a higher likelihood of developing the condition.
Once knee osteoarthritis occurs, it is more likely to worsen if you have a varus alignment.
The medial meniscus is affected in varus malalignment.
Contrasting the Two
Identifying valgus (knock knee) or varus (bow leg) alignment can sometimes be easier from a distance.
With knock knees, the legs curve inward, causing the knees to touch while the ankles remain apart.
In contrast, bow-legs curve outward like a bow, leaving a noticeable gap between the knees when the feet are together.
In children, knock knees often straighten out over time, though some adults may retain traces of the condition. Bowing can cause children to become pigeon-toed, with toes pointing inward.
Causes
Valgus knee can be traced to a number of factors, including:
- Arthritis, especially rheumatoid arthritis
- Benign bone tumor
- Congenital conditions (present at birth)
- Fractures that healed improperly
- Kidney failure
- Physical trauma
- Rickets (a bone disease caused by a lack of vitamin D)
Likewise, a number of illnesses and conditions can cause a varus knee:
- Abnormal bone development (known as bone dysplasia)
- Damage to the growth plate
- Fluoride poisoning
- Fractures that healed improperly
- Lead poisoning
- Paget’s disease (a metabolic disease affecting the way bones break down and rebuild)
- Rickets
- Blount’s disease, a growth disorder of the shinbone
Valgus or varus alignment of the knees is frequently seen in toddlers. The legs usually straighten out as the child grows and matures.
Symptoms
Knee or hip pain are common to both valgus and varus alignment. So are other symptoms, including:
- Difficulty walking or running
- Knee instability, a feeling that the knee joint is twisting and about to “give out”
- Reduced range of motion in the hips
Diagnosis
The two knee conditions are diagnosed in a similar manner. First, an orthopedic specialist gathers your medical/family medical history and asks about your current health and any pre-existing conditions.
A physical exam of the legs often helps make a diagnosis. An X-ray is done to confirm it.
Imaging Option for Kids
Parents who worry about exposing a child to radiation often opt for EOS imaging. This test takes full-body, 3D images while a patient assumes a sitting or standing position. It emits some radiation, but less than an X-ray.
Treatment
When treatment for a child or adult is necessary, the first step is to correct any underlying condition that’s causing the misalignment. For example, a child diagnosed with nutritional rickets is usually treated with vitamin D and calcium to strengthen the bones.
Bracing is a go-to choice to help support the knee and straighten both types of misalignment. Physical therapy may be provided to help improve strength and function.
Severe cases may warrant a more aggressive approach in the form of an osteotomy, a surgical procedure in which bone is cut and then realigned. When necessary, adjustments are made to the femur (thighbone) and tibia (shinbone).
Many children naturally outgrow their misalignment. Affected children have bow legs until about age 3 and knock knees until they’re about 7 or 8. After that, no further treatment is required.
Some children remain knock kneed until they’re teens. Even some adults may remain slightly knock kneed.
If parents remain concerned about their child’s legs as they grow up, parents could take pictures every six months to see if there are any visible changes.