A condition known as genu valgum, or knock knees, is an alignment issue where the knees angle inward and touch when the feet are separated. This common lower-limb variation often raises the concern of whether the inward angling of the legs makes a person shorter. While the condition does not decrease the actual length of the leg bones, it directly influences the overall vertical measurement of a person’s standing height. Understanding genu valgum involves exploring its anatomical basis, measuring its severity, and examining corrective options that may restore functional stature.
Understanding Genu Valgum
Genu valgum is characterized by an altered mechanical axis of the lower limb, causing the knees to move toward the midline of the body. This alignment results in the ankles being positioned further apart when the individual stands with the knees touching. The condition is often classified into two main types based on its origin and progression.
Most cases are considered physiological genu valgum, representing a normal developmental stage in children that typically begins around age two, peaks between ages three and four, and naturally resolves by age seven or eight. The pathological form persists beyond this age range or is caused by an underlying medical issue, such as nutritional deficiencies like rickets, trauma, or certain skeletal dysplasias. In pathological cases, the change in the mechanical axis places uneven pressure on the knee joint, which can lead to pain and altered gait over time.
The Direct Impact on Measured Height
Knock knees do not physically shorten the femur or tibia bones, meaning the true skeletal height remains unchanged. However, they significantly reduce the functional or measured height due to the body’s compensatory postural adjustments. When the knees angle inward, the body shifts its center of gravity to maintain balance, often resulting in a slight flexion, or bending, of the knees and a minor tilting of the pelvis.
This biomechanical compensation effectively lowers the overall vertical line of the body’s stance. Measured height is the straight vertical line from the floor to the top of the head; any flex or inward angle in the legs shortens this distance. Correcting the angular deformity straightens the legs, allowing the individual to stand fully upright and restoring the functional height lost due to the bent-knee posture.
Assessing Severity and Common Causes
Physicians determine the degree of genu valgum using the intermalleolar distance. This measurement is the space between the medial malleoli, or inner ankle bones, when a standing patient brings their knees together. An intermalleolar distance greater than 8 centimeters is considered outside the normal range for children past the age of physiological correction and may warrant further evaluation.
The most frequent causes of knock knees are developmental and resolve spontaneously as a child grows. When the condition persists or is severe, however, physicians look for underlying issues. Pathological causes include metabolic bone diseases, such as rickets from vitamin D deficiency, or skeletal dysplasias that affect bone and cartilage growth. Asymmetrical genu valgum, where one leg is more affected than the other, may also point toward a history of prior growth plate injury.
Treatment Options and Postural Correction
Treatment for genu valgum depends heavily on the patient’s age, the cause, and the severity of the alignment issue. For children with physiological knock knees, observation is the standard approach, as the condition usually self-corrects without intervention before the age of eight. Persistent or pathological cases require active management to prevent future joint problems and restore proper alignment.
Non-surgical approaches include physical therapy focused on strengthening hip and thigh muscles to better control knee mechanics and gait. Orthotics or specialized shoe inserts may also be prescribed to adjust foot posture and evenly distribute weight, though they do not correct the underlying bone alignment. For children with significant remaining growth, a procedure called guided growth, or hemiepiphysiodesis, may be performed.
This surgery involves placing a small metal plate or screw on one side of the growth plate near the knee to temporarily slow growth on that side, allowing the other side to catch up and straighten the limb over time. For adolescents who have finished growing or for severe adult cases, an osteotomy is performed, which involves cutting and realigning the bone to correct the angle. Successful correction of the mechanical axis allows for a straighter standing posture and the recovery of functional height lost due to the original inward knee angle.