A varus deformity is a bone or joint alignment where part of the limb angles inward toward the body’s midline, creating an outward-bowing appearance. The most familiar example is bowleggedness at the knee, but varus alignment can occur at the hip, foot, or elbow as well. In many cases it’s a normal phase of childhood development, but when it persists or develops later in life, it can accelerate joint damage and change the way you walk.
How Varus Alignment Works
In a normally aligned leg, the mechanical axis runs in a roughly straight line from the center of the hip through the center of the knee to the center of the ankle. In varus alignment, the joint angles so that the segment below the joint tilts inward. At the knee, this pushes the lower leg toward the midline while the knees themselves drift apart, producing the classic bowed appearance. Clinically, a varus knee deformity is defined when the angle between the mechanical axes of the thighbone and shinbone reaches 3 degrees or more.
The same principle applies elsewhere in the body. At the hip, the condition is called coxa vara, where the angle between the neck and shaft of the thighbone drops below 120 degrees. This shortens the limb and produces a waddling gait. At the big toe, hallux varus angles the toe inward away from the other toes. In each case, “varus” simply describes the direction: the part below the joint tips toward the midline.
When Bowlegs Are Normal in Children
Nearly all babies are born with some degree of bowleggedness. The cramped position in the uterus curves the legs, and this is considered physiologic genu varum, a normal developmental phase. Most children’s legs straighten on their own by about 18 months, and the condition typically resolves fully by age 2. If the bowing hasn’t improved by that point, it may signal something beyond normal growth.
Causes of Persistent or Adult Varus Deformity
When varus alignment persists past early childhood or develops in adulthood, several conditions can be responsible.
Blount’s Disease
Blount’s disease is a growth disorder where the inner part of the growth plate at the top of the shinbone doesn’t develop properly. This disrupts normal bone formation on the medial (inner) side, causing progressive bowing. It’s classified as early onset (before age 4) or late onset, with the late form further divided into juvenile and adolescent types. Early stages can sometimes reverse, but advanced disease is harder to treat, with recurrence rates reaching over 70% in the most severe category.
Rickets and Nutritional Deficiencies
Rickets, most often caused by vitamin D deficiency, weakens developing bone by depleting calcium and phosphorus. Without enough of these minerals, bones soften and bend under body weight. In toddlers, this can exaggerate the natural bowing of the legs into a lasting varus deformity. Less commonly, rickets results from the kidneys wasting phosphorus rather than from a dietary shortage. Both forms leave bones too soft to hold their shape during growth.
Osteoarthritis and Aging
In adults, varus deformity most often develops alongside osteoarthritis of the inner (medial) compartment of the knee. As cartilage wears down on the inside of the joint, the bones settle closer together on that side, gradually tilting the leg into a bowed position. The relationship runs both ways: varus alignment concentrates force on the inner compartment, and that concentrated force wears cartilage faster. Long-term pressure on the medial compartment raises the incidence of arthritis in that area to roughly 10 times the rate seen on the outer side of the knee.
How Varus Alignment Changes Your Gait
Walking with varus knees places disproportionate load on the inner edge of the joint with every step. This force, measured as the knee adduction moment, is consistently elevated in people with varus alignment and is directly linked to faster cartilage breakdown. To compensate, the body makes several automatic adjustments. Many people develop a lateral trunk lean, shifting the torso over the affected leg to reduce stress on the medial compartment. Others adopt a wider toe-out angle or develop a visible lateral thrust, where the knee visibly snaps outward during weight-bearing.
These compensations don’t stay confined to the knee. Research shows that varus knee alignment tends to push the hindfoot into a compensatory position as well, altering the mechanics of the ankle and foot over time. This chain of adjustments can create new sources of pain and instability well beyond the original problem joint.
How Varus Deformity Is Measured
Diagnosis starts with a standing X-ray of the full leg. The key measurement is the hip-knee-ankle (HKA) angle: a line drawn from the center of the hip to the center of the knee, then from the center of the knee to the center of the ankle. In a normally aligned leg, these lines form close to a straight 180-degree line. Any inward deviation of 3 degrees or more is classified as varus. Doctors may also use a simpler measurement of the angle between the thighbone shaft and shinbone shaft, reporting the result as degrees of deviation from neutral.
Conservative Management
For mild varus alignment, especially when accompanied by early knee arthritis, non-surgical options aim to redistribute load across the joint. Lateral wedge insoles, placed in your shoes, tilt the foot slightly to shift pressure away from the inner knee. However, studies show these insoles produce only a modest 5% to 6% reduction in medial loading, which may not be enough to meaningfully reduce pain for many people. Physical therapy focused on strengthening the muscles around the hip and thigh can help stabilize the joint and improve gait patterns. Weight management also reduces the total force passing through the knee with each step.
In children with Blount’s disease or rickets, bracing and splints can guide bone growth if started early enough. Treating the underlying nutritional deficiency in rickets, primarily with vitamin D and calcium supplementation, allows bone to re-mineralize and can correct mild deformities during the growth period.
Surgical Options for Severe Cases
When conservative approaches fall short, surgery can physically realign the leg. The two most common procedures for varus knees are high tibial osteotomy and knee replacement.
High Tibial Osteotomy
High tibial osteotomy (HTO) involves cutting the top of the shinbone and repositioning it to shift the leg’s weight-bearing line away from the damaged inner compartment. The ideal candidate is typically younger (under 56), at a healthy or slightly above-normal weight, with a good range of motion (at least 120 degrees of knee bend) and only mild to moderate arthritis limited to the inner compartment. Correction aims for a slight overcorrection into 6 to 14 degrees of outward (valgus) alignment, because undercorrection to less than 5 degrees is associated with a failure rate above 60%.
After successful osteotomy, patients consistently show reduced medial loading during walking, less lateral trunk lean, and decreased lateral thrust. For younger, active patients, HTO is generally preferred over partial knee replacement because it preserves the natural joint and allows return to higher activity levels.
Knee Replacement
For more advanced arthritis with significant varus deformity, total knee replacement corrects alignment by resurfacing the joint entirely. Even in cases of severe varus, a standard implant is usually sufficient, though some patients require a more constrained design to achieve a stable, balanced knee. Long-term implant survival rates remain high even when the starting deformity is significant, making this a reliable option for older or less active patients whose arthritis has progressed beyond what osteotomy can address.