Knock knees are a leg alignment where the knees angle inward and touch or nearly touch each other while the ankles remain apart. The medical term is genu valgum. In children, this is almost always a normal phase of growth that corrects on its own. In adults, persistent or worsening knock knees can lead to knee pain, instability, and eventually arthritis in the outer part of the knee joint.
Why Most Children Get Knock Knees
Nearly all children go through a knock-knee phase as part of normal leg development. Around age 2 to 3, a child’s legs naturally shift from a slightly bowlegged position into a knock-kneed alignment. This inward angle peaks over the next one to two years, typically around age 3 to 4. After age 6, the knees gradually straighten into a more neutral position, and very little angular change occurs after that point.
During this window, the alignment can look dramatic, especially when a child stands with knees together and ankles far apart. But in the vast majority of cases, no treatment is needed. The growth plates around the knee are simply developing at slightly different rates on each side, and they even out with time.
When Knock Knees Are Not Normal
Knock knees that persist past age 7 or 8, appear only on one side, or get progressively worse may signal an underlying problem. Potential causes of pathological knock knees include rickets (from vitamin D or calcium deficiency), other metabolic bone conditions, skeletal dysplasias, and injuries to the growth plate near the knee. Obesity is one of the strongest risk factors: a study of over 1,000 schoolchildren found that obese children were roughly 76 times more likely to have knock knees than children at a normal weight, while overweight children had about 6 times the risk.
A child whose knock knees are worsening, causing pain, or accompanied by a limp or unusual gait pattern warrants evaluation. In rare cases, increasing inward angulation can cause the kneecap to shift outward, an out-toed walking pattern, and the knees rubbing together during movement.
Symptoms in Children and Adults
Most people with mild knock knees have no symptoms at all and no limitations in physical activity. When symptoms do appear, they typically show up as pain along the inner side of the knee or ankle, sometimes preceded by flat feet.
Adults who have been knock-kneed for years face a different set of problems. The inward angle shifts weight-bearing stress onto the outer compartment of the knee while stretching the ligament on the inner side. Over time, this combination can cause chronic pain, a feeling of knee instability, kneecap tracking problems, and arthritis in the lateral (outer) portion of the knee. These issues tend to develop gradually and worsen with high-impact activity or prolonged standing.
How Knock Knees Are Diagnosed
Diagnosis starts with a physical exam. With the child or adult standing with knees together, the distance between the inner ankle bones (the intermalleolar distance) gives a simple measure of severity. A standing X-ray of the full leg, from hip to ankle, allows precise measurement of the angle and helps determine whether the source of the misalignment is in the thighbone, the shinbone, or both. For children, the X-ray also shows the status of the growth plates, which is critical for deciding whether and when to intervene.
Exercise and Physical Therapy
Exercise cannot change bone alignment in adults or older children whose growth plates have closed. But strengthening certain muscle groups can reduce pain and improve how the knee tracks during movement. The key targets are the hip external rotators (the muscles that turn your thigh outward), the muscles along the outer hip, and the core. Weakness in these areas allows the knee to collapse inward more during walking, running, and squatting, which adds stress to the joint.
Neuromuscular training, which focuses on teaching the body to maintain better alignment between the trunk and lower limbs during functional movements, plays an important role. Stretching the inner thigh muscles, hamstrings, and the band of tissue along the outer thigh can also help by reducing tightness that pulls the knee into a more pronounced inward position. For children still in the developmental phase, these exercises are rarely necessary since the alignment typically self-corrects.
Guided Growth Surgery for Children
When knock knees in a child are pathological and unlikely to resolve, a procedure called guided growth (or temporary hemiepiphysiodesis) can correct the alignment while the child is still growing. A small metal plate is placed on one side of the growth plate near the knee, which slows growth on that side and allows the other side to “catch up,” gradually straightening the leg. The plate is removed once the alignment is corrected.
A multinational study of 537 patients found that 70% of those treated for thighbone-side deformities achieved standard alignment, while 80% of those treated on the shinbone side reached the target. Children who had at least three years of growth remaining when the plate was placed had significantly better outcomes. The average age at the time of surgery was about 11 years, and the procedure works best when there is enough growth left for the correction to take full effect.
Corrective Surgery for Adults
Adults whose growth plates have long since closed cannot benefit from guided growth. Instead, corrective bone surgery (osteotomy) is the primary option for those with significant symptoms or progressive arthritis. The procedure involves cutting and realigning the lower end of the thighbone to shift weight-bearing forces back toward the center of the knee.
Recovery follows a fairly predictable pattern. Patients are typically limited to partial weight-bearing for the first 5 to 6 weeks, then gradually progress to full weight-bearing by 6 to 12 weeks. Returning to sports takes longer, ranging from about 8 to 17 months after surgery. Studies show that 70% to 100% of patients eventually return to sports, and roughly 42% to 100% get back to their previous level of activity. The wide range reflects differences in age, the severity of the original misalignment, and whether arthritis had already developed before surgery.
Long-Term Outlook
For children going through the normal developmental phase, the outlook is excellent. The vast majority straighten out by age 6 or 7 with no lasting effects. Children with pathological knock knees who are treated with guided growth during the right window also tend to do well, particularly when the procedure is timed to take advantage of remaining growth.
For adults, the main concern is cumulative wear on the outer knee compartment. Years of abnormal loading can lead to cartilage breakdown that is difficult to reverse. Early intervention with strengthening exercises, activity modification, and corrective surgery when appropriate can slow or prevent this progression. The longer significant malalignment goes unaddressed, the greater the risk of irreversible joint damage.