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Knock Knees | Genu Valgum

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Knock Knees Surgery before and after

Moderate Knock Knees (Genu Valgum)

Walking with Knock Knees can be painful and / or annoying, it also produces an abnormal gait.

In order to avoid hitting their knees together, people may "scissor walk", swinging their legs with each step, or adopt an abnormally wide stance.

Knock Knees Surgery

The blue lines in this figure are drawn from the middle of the femoral head to the center of the ankle, indicating the weight-bearing mechanical axis. Before knock knees surgery, the outside of the knees become overloaded, this leads to arthritis. After the knock knees surgery, the lines now pass through the center of the knee and the patient's weight is evenly distributed

Knock Knees Surgery
Knock Knees Limb lengthening

Patient With Femoral Rotation and Knock Knees

Knock Knees Surgery - Correction through Femur + Tibia

What is Knock Knees / Genu Valgum?

“Knock knees” (genu valgum or valgus knees) is a common condition that affects both children and adults. This malalignment causes the knees to “knock” together while standing and walking. Knock knees make it difficult to stand with the feet together.


People with this condition will often develop painful knee arthritis. Knock knees can affect the ankles and can cause flat feet. 

Knock knees can be associated with other problems including patellar instability and rotational abnormalities of the legs. These combined malalignments make walking and exercising particularly difficult

What Causes Knock Knees?

Most knock knees are congenital. This means that people are born with the deformity, and it becomes more obvious with growth. After a child reaches puberty, knock knees are not normal.


In some cases, there is a long family history of valgus making this a genetic variety. Many patients are motivated to seek treatment because an older family member has always suffered from “knee problems.”

In the figure below, we see the weight-bearing mechanical axis indicated by the vertical lines. When someone has knock knees, the outside (lateral side) of the knees become overloaded which leads to arthritis and the kneecap pulls laterally creating knee pain.

Symptoms Of Knock Knees

If your feet don’t come together when your knees are touching, then you may have knock knees. Other symptoms of knock knees include:

-Awkward walking

-Difficulty running

-Knee pain

-Patellar instability, popping/dislocating kneecap

-Social anxiety over the appearance of the legs

Knock Knees may also be accompanied by a rotational deformity which may not be initially detected. 

Knock Knees consistently lead to arthritis over time, this progression can be slowed or stopped through treatment.

Knock Knees Treatment

The goal of knock knees surgery is to balance the knees and slow or prevent arthritis. Having straight legs improves overall function and reduces or eliminates pain. Most noticeable is a major cosmetic improvement of leg appearance which boosts self-esteem.

Knock knees is a structural problem with the shape of the bone. The treatment needs to address this fundamentally. Surgical correction is the only way to straighten knock knees.


The surgery needed depends on the age of the patient and on the severity of the deformity. In children, the surgery is often very limited to simply tethering the growth plate inducing it to grow straight. In adults, the femur, and sometimes the tibia bone, need to be cracked by making an osteotomy and then the bone needs to be pushed into a straight alignment. The crack in the bone needs to be held in this new position with metal hardware while it heals. The metal implants used include plates, intramedullary nails, or external fixators.

Each patient is an individual with a unique alignment that requires careful evaluation and customized surgical planning. The origin of the valgus, the relative limb lengths, the presence of other problems like rotational deformities or patellar instability, and specific patient factors will weigh into the decision of which bone to correct and which metal device to use.

Below, we see the correction of a knock knee through a Distal Femoral Osteotomy using a plate, as well as a tibial osteotomy using a rod. This is just one of the many personalized treatments available to our patients.

The presence of a dislocating kneecap along with knock knee deformity requires special attention including the recruitment of colleagues specialized in patellofemoral reconstruction.


These complex patellofemoral reconstruction procedures provide comprehensive care to the patient by pooling the skill sets of two expert surgeons. This individualized treatment approach has led to outstanding results.


Surgery is performed at the Hospital for Special Surgery in New York City. Dr. Fragomen personally performs all of the procedures and is supported by a professional surgical team. Patients are admitted to the hospital after surgery for an average of 2 nights where they will receive multimodal pain control from the HSS pain team and physical therapy for crutch training.


Patients can expect to be on crutches for about 6 weeks. Once the osteotomy site has healed, patients may resume unrestricted physical activity. Eventually the rods and plates will need to be removed in an ambulatory setting. 

Medical Questions

Dr. Fragomen:

Erica Lenihan, RN:

Zac Edelman, PA:

Eric Lau, PA:

Scheduling and Insurance Inquiries

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