Knee Malalignment

Ideally, body weight is distributed relatively evenly through the knee joint when a person stands or walks. Knee malalignment occurs when the bones of the leg do not form a normal mechanical alignment through the hip, knee, and ankle.

There are two common forms of knee malalignment called varus alignment and valgus alignment. Varus alignment occurs when the knees angle outward relative to the hips and ankles. This is sometimes described as being bow-legged. Valgus alignment occurs when the knees angle inward toward each other and is sometimes called knock-kneed alignment.

These alignment changes can increase pressure on one side of the knee. Varus alignment generally places additional stress on the inner, or medial, portion of the knee. Valgus alignment typically increases stress on the outer, or lateral, portion of the knee.

The degree of malalignment can vary significantly. Mild malalignment may cause few or no symptoms, while more significant abnormalities can contribute to progressive joint pain and damage.

Knee malalignment can develop for several reasons. In some people, the bones of the legs gradually develop into a bow-legged or knock-kneed position as they grow. Although changes in leg alignment are common during early childhood, the legs usually become more normally aligned as a child matures. In some individuals, however, abnormal alignment persists into adolescence or adulthood. Genetics may also play a role because inherited differences in bone shape, joint structure, and leg alignment can make some people more likely to develop knee malalignment.

Previous injuries are another potential cause. A fracture involving the leg bones or knee joint may heal in an abnormal position, altering how weight passes through the leg. Ligament injuries can also change knee mechanics and contribute to instability or abnormal loading.

Arthritis may both contribute to and result from knee malalignment. As cartilage wears away on one side of the knee, the joint space can narrow unevenly. This can gradually change the alignment of the leg. At the same time, existing malalignment can increase pressure on one portion of the knee and accelerate cartilage degeneration in that area.

Other contributing factors may include growth plate injuries during childhood, congenital bone abnormalities, certain metabolic bone conditions, and previous knee surgery.

Symptoms depend on the severity of the alignment abnormality and the amount of damage within the knee. Some people may notice visible bowing or inward angling of the legs without experiencing significant pain.

Pain is the most common symptom. It may be concentrated on the inner or outer side of the knee depending on the direction of the malalignment. As cartilage damage progresses, patients may also experience grinding, catching, or clicking sensations within the knee.

Other symptoms may include stiffness, swelling, difficulty walking, reduced range of motion, or a feeling that the knee is unstable. Some individuals notice that symptoms become more pronounced after prolonged standing, walking, running, or other weight-bearing activities

Diagnosis typically begins with a review of the patient’s symptoms, medical history, previous injuries, and activity level. Your orthopedic physician will examine the alignment of the legs while you are standing and may evaluate walking mechanics, knee stability, range of motion, and areas of tenderness.

X-rays are commonly used to evaluate the bones and joint spaces. Full-length, weight-bearing X-rays of the legs can be particularly helpful because they allow the physician to evaluate the mechanical axis from the hip through the knee and ankle.

Magnetic resonance imaging, or MRI, may be recommended when additional information is needed about cartilage, menisci, ligaments, or other soft tissues within the knee.