Valgus knee, commonly known as “knock-knees,” is a condition where the knees angle inward, often touching or nearly touching, even when a person stands with their feet together. This alignment contrasts with typical leg alignment where the knees and ankles are in a straighter line. It is characterized by a valgus angle (Q angle) of 10 degrees or more.
Identifying Valgus Knee
Observing valgus knee typically involves a visual assessment of leg alignment. When an individual stands with their feet together, their knees will visibly touch or come very close, while their ankles remain separated. This creates an “X-leg” appearance, distinguishing it from a “bow-legged” or “O-leg” pattern where the knees are apart.
Anatomically, valgus knee involves an inward angling of the femur (thigh bone) and an outward angling of the tibia (shin bone) relative to the femur. This misalignment shifts the load-bearing axis of the leg towards the outside of the knee joint. Medical professionals may measure the intermalleolar distance, which is the space between the inner ankles when the knees are touching, to assess the degree of this inward angulation.
Common Causes and Risk Factors
Valgus knee can arise from a variety of factors, including developmental issues, underlying medical conditions, or injuries. In toddlers, a physiological valgus knee is common, often peaking between ages 3 and 4, and typically resolves naturally by age 7. This spontaneous correction occurs in about 99% of cases by age 7 or 8.
Beyond typical development, certain medical conditions can lead to valgus knee. These include rickets, a bone disease caused by a severe lack of vitamin D and calcium, and other metabolic bone diseases. Genetic disorders, such as osteochondrodysplasia, can also manifest with genu valgum as a skeletal symptom.
Trauma, such as an injury to growth plates in children or a malunion of a fracture, can contribute to valgus knee. In adults, prior knee surgery can also lead to a valgus deformity. Arthritis, especially rheumatoid arthritis, is another common cause, and osteoarthritis can also lead to or worsen the condition.
Risk factors increasing the likelihood of developing valgus knee include obesity, which places additional stress on the knees, and a family history of valgus knee or other bony deformities.
Potential Symptoms and Complications
Valgus knee can present with various physical symptoms and may lead to long-term complications due to altered leg biomechanics. A common symptom is knee pain, particularly on the outer side of the knee, which can be a result of increased stress on the lateral compartment. Individuals may also experience difficulty walking or running, a feeling of instability in the knee, joint stiffness, and reduced range of motion.
The misalignment of valgus knee places increased stress on the lateral (outer) compartment of the knee joint. This can accelerate cartilage wear, raising the risk of developing or worsening osteoarthritis. Other potential complications include patellofemoral pain syndrome, which causes pain around the kneecap, and ligament strain due to abnormal forces on the knee joint. The altered alignment can also impact the entire kinetic chain of the leg, leading to internal hip rotation and excessive foot pronation, which can cause pain in the hips, ankles, or feet.
Diagnosis and Management Options
Diagnosing valgus knee typically begins with a physical examination. A healthcare provider will assess leg alignment, often measuring the Q-angle or intermalleolar distance to quantify the misalignment. Observing the patient’s gait can also reveal dynamic instabilities.
Radiographic imaging, particularly standing weight-bearing X-rays, is used to confirm the diagnosis and assess the mechanical axis and angular deformities of the femur and tibia. In some cases, if soft tissue damage or other underlying issues are suspected, an MRI may be used for a more detailed assessment of ligaments and cartilage.
Non-surgical management is often the first approach, especially for physiological valgus knee in young children, where observation is recommended as it often resolves spontaneously by age 7. Physical therapy strengthens muscles around the knees and hips, improving alignment, and reducing joint stress. Orthotics, such as shoe inserts or knee braces, may also provide external support and help correct gait.
Weight management is advised for overweight individuals to reduce stress on the knees. Pain management can involve over-the-counter medications like NSAIDs or the application of ice or heat.
Surgical management is considered for more severe cases, persistent pain, or functional limitations, especially when the valgus angle exceeds 15 degrees. In growing children, guided growth surgery involves placing a small metal plate on one side of the growth plate to guide bone growth and correct alignment. For adolescents or adults, an osteotomy is a common surgical procedure where a wedge of bone is either removed or added to realign the bone to correct the axis to neutral and redistribute weight across the joint. In severe cases with advanced arthritis, a total knee replacement may be performed to correct the deformity and address joint damage.