A condition in which the knees bend inward, touching (or “knocking”) even when a person is standing with their ankles apart, knock knee can affect people of all ages. Knock knee, also known as genu valgum, is a mal-alignment of the knee with various causes, often leading to pain and degeneration of the knee if left untreated. Knock-knees can be congenital, developmental, or post-traumatic. The common theme that pervades all age groups is that the knee is abnormally loaded which can lead to pain, increasing deformity, instability, and progressive degeneration. Correction of the deformity leads to improved knee mechanics, better walking, less pain, and prevents the rapid progression of damage to the knee.
Adult patients who have had knock-knee for many years overload the outside (lateral compartment) and stretch the inside (medial collateral ligament) leading to pain, instability, and arthritis. To prevent and delay the need for joint replacement, knee realignment should be done with osteotomy.
What Is Knock Knee?
Knock knee is a condition in which a person’s knees angle toward each other and touch (“knock”), even when the person is standing with their ankles apart. While temporarily knocked knees is a standard developmental stage in most children, this often self-corrects by age seven or eight. Knock knees that persist beyond six years of age, are severe, or affect one leg significantly more than the other may be a sign of knock knee syndrome.
Knock knee that falls outside the normal developmental patterns may be caused by disease, infection, or other conditions. In these cases, orthopedic intervention may be required to treat the knock knee condition.
Is Knock Knee Normal?
Most children experience normal angular changes in their legs as they grow. When a child is born, they are typically bowlegged until they begin walking at 12-18 months. By the time the child is two to three years old, his legs should begin to angle inward, making him knock-kneed. However, knock-knee usually self-corrects by the time a child is seven to eight years old.
If the angular profile (the leg’s angle from hip to foot) falls outside normal patterns, worsens over time, or is present on only one side of the body, it may be indicative of a more serious form of knock knee requiring further evaluation.
What causes knock knee?
While knock knee is part of a child’s normal growth pattern, persistent forms of knock knee may stem from an underlying disease, infection, or injury. Some common causes of knock knee include:
Metabolic disease
Renal failure
Physical trauma
Arthritis, particularly in the knee
Bone infection (osteomyelitis)
Rickets (a bone-weakening disease caused by lack of vitamin D)
Congenital
Growth plate injury
Benign bone tumors
Fractures that heal with deformity (malunion)
Being overweight or obese can also put extra pressure on the knees and contribute to knock knee.
Symptoms of Knock Knee Syndrome
The most commonly observed symptom of knock knee is a separation of the ankles when the knees are together. Other symptoms of knock knee often arise as a result of the walking gait adopted by individuals with knock knee. These symptoms may include:
Pain in knees, feet, hips, and ankles
A limp when walking
Stiff or sore joints
Feet do not touch when standing with knees together
Knee or hip pain
Reduced range of motion in hips
Difficulty walking or running
Knee instability
Progressive knee arthritis in adults
Patients or parents may be unhappy with aesthetics
Other symptoms from underlying conditions may also be present.
How is Knock Knee Diagnosed?
Knock knee is diagnosed through a thorough review of an individual’s medical history, pre-existing conditions, family history, and current health. It also includes a physical examination of the patient’s legs and observations of their gait. Diagnosis also includes a standing alignment X-ray. A standing alignment X-ray or EOS image produces an image of the leg from hip to ankle which helps the orthopedist locate the mechanical axis of the deformity as well as its location. On the x-rays, the magnitude and location of the deformity is identified.
How Is Knock Knee Treated?
If the underlying condition of knock knee is due to disease or infection, that disease or condition will be addressed before or as orthopedic correction begins. Treatment for mild cases of knock knee in children or adolescents may include braces to help bones grow in the correct position. If a gradual correction does not occur, surgery may be recommended.
In the growing child, guided growth minimal incision surgery may be used to encourage the limb to gradually grow straight. Osteotomy, in which the femur is cut, and then realigned may be needed. In some cases, the surgeon also places an external fixator. With external fixators, pins are inserted into the bone and protrude out of the body to attach to an external stabilizing structure. Physical therapy is also an important part of treatment, especially in cases where surgery has occurred.
In skeletally mature adolescents and in adults, osteotomy is the recommended treatment to straighten the leg. X-rays are used to determine the location and magnitude of the deformity. In most cases, we treat the femur, but there are situations when the tibia or both femur and tibia are treated. When moderate deformity is present, the osteotomy is typically stabilized with internal fixation (plate or rod). When the mal-alignment is more severe, gradual realignment of the limb through the osteotomy may be done with an external fixator.
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Joanne who had single stage osseointegration after hip disarticulation has a prosthetic that moves at both the hip and knee joints. At 8 months post surgery, she has achieved huge functional and quality of life improvements #osseointegrationlimbreplacement https://www.hss.edu/osseointegration-limb-replacement.asp #osseointegration #amputationsurgery #amputee #cyborgsworld @cyborgsworld #amputeelife #amputeestrong #amputation #osseointegrationUSA www.osseointegrationUSA.com #prostheticlimb #prostheticleg #prostheticsandorthotics #limbreplacementsurgery #limbreplacement #osseointegrationaustralia #osseointegrationswholift #Rozbruch #aaos #llrs #orthopedicsurgery #liveyourbestlife #orthopedicsurgeon #hospitalforspecialsurgery #limblengthening @hspecialsurgery @limbdeformity @reifmd #SRobertRozbruchMD www.limblengthening.com www.hss.edu/limblengthening www.hss.edu/LSARC #hssLLCRS #HSSlimbLengthening
Sherry 3 years post percutaneous single stage osseointegration. With compromised skin and a unique residual limb shape, she was not doing well with a socket. Osseointegration limb replacement has improved her mobility and life quality #osseointegrationlimbreplacement https://www.hss.edu/osseointegration-limb-replacement.asp #osseointegration #amputationsurgery #amputee #cyborgsworld @cyborgsworld #amputeelife #amputeestrong #amputation #osseointegrationUSA www.osseointegrationUSA.com #prostheticlimb #prostheticleg #prostheticsandorthotics #limbreplacementsurgery #limbreplacement #osseointegrationaustralia #osseointegrationswholift #Rozbruch #aaos #llrs #orthopedicsurgery #liveyourbestlife #orthopedicsurgeon #hospitalforspecialsurgery #limblengthening @hspecialsurgery @limbdeformity @reifmd #SRobertRozbruchMD www.limblengthening.com www.hss.edu/limblengthening www.hss.edu/LSARC #hssLLCRS #HSSlimbLengthening
Kevin’s first steps 3 months post single stage osseointegration. With a short residual leg, he had great difficulty with a socket. An alternative to a transfemoral amputation, Osseointegration will preserve his knee. #osseointegrationlimbreplacement https://www.hss.edu/osseointegration-limb-replacement.asp #osseointegration #amputationsurgery #amputee #cyborgsworld @cyborgsworld #amputeelife #amputeestrong #amputation #osseointegrationUSA www.osseointegrationUSA.com #prostheticlimb #prostheticleg #prostheticsandorthotics #limbreplacementsurgery #limbreplacement #osseointegrationaustralia #osseointegrationswholift #Rozbruch #aaos #llrs #orthopedicsurgery #liveyourbestlife #orthopedicsurgeon #hospitalforspecialsurgery #limblengthening @hspecialsurgery @limbdeformity @reifmd #SRobertRozbruchMD www.limblengthening.com www.hss.edu/limblengthening www.hss.edu/LSARC #hssLLCRS #HSSlimbLengthening
Joanne @a_hip_journey after an osseointegration limb replacement hip disarticulation. She shared her experience with a live demo our HSS advances in amputation surgery course in January 2023. I preserved some proximal femur for bone stock. She is ambulating quite well independently at 8 months postop single stage osseointegration Her prosthetic has both a hip and knee joint #osseointegrationlimbreplacement https://www.hss.edu/osseointegration-limb-replacement.asp #osseointegration #amputationsurgery #amputee #cyborgsworld @cyborgsworld #amputeelife #amputeestrong #amputation #osseointegrationUSA www.osseointegrationUSA.com #prostheticlimb #prostheticleg #prostheticsandorthotics #limbreplacementsurgery #limbreplacement #osseointegrationaustralia #osseointegrationswholift #Rozbruch #aaos #llrs #orthopedicsurgery #liveyourbestlife #orthopedicsurgeon #hospitalforspecialsurgery #limblengthening @hspecialsurgery @limbdeformity @reifmd #SRobertRozbruchMD www.limblengthening.com www.hss.edu/limblengthening www.hss.edu/LSARC #hssLLCRS #HSSlimbLengthening
Mark from Utah is 11 weeks post single stage osseointegration limb replacement surgery. He is very excited to get back to his super active lifestyle. I expect that he will become an example and inspiration to amputees. #osseointegrationlimbreplacement https://www.hss.edu/osseointegration-limb-replacement.asp #osseointegration #amputationsurgery #amputee #cyborgsworld @cyborgsworld #amputeelife #amputeestrong #amputation #osseointegrationUSA www.osseointegrationUSA.com #prostheticlimb #prostheticleg #prostheticsandorthotics #limbreplacementsurgery #limbreplacement #osseointegrationaustralia #osseointegrationswholift #Rozbruch #aaos #llrs #orthopedicsurgery #liveyourbestlife #orthopedicsurgeon #hospitalforspecialsurgery #limblengthening @hspecialsurgery @limbdeformity @reifmd #SRobertRozbruchMD www.limblengthening.com www.hss.edu/limblengthening www.hss.edu/LSARC #hssLLCRS #hsslimblengthening