When I ran my first long-distance race, I felt like an athlete for the first time. Training for and completing a 15-kilometer run through the worst of a Canadian winter tested my will, as well as my heart, lungs, and legs. Then somebody showed me a video of my finish. Instead of a fierce warrior, I saw a slow, tired woman dragging herself across the finish line, her knees collapsing in towards one another with every step.
Valgus knee, also known as ‘knock-knees’ or genu valgum, is a common condition where the knees angle in towards the midline. This can lead to foot pronation on the affected side and is sometimes associated with increased lordosis, which is the normal curve of the lower back. Increased lordosis will cause a forward tilt of the pelvis, referred to as anterior pelvic tilt.
Knee valgus is a normal presentation in early childhood. Outside of this stage, if it presents on one side or comes on suddenly, there may be an underlying problem that may require treatment.
Difference between valgus and varus knee
In a bilateral valgus knee, the knees angle in towards one another and likely touch in a standing position. This causes the lower legs to splay out, with the feet spaced apart. Knee valgus is also sometimes referred to as knee abduction. This describes a movement of the lower leg and foot away from the midline. A valgus knee may present with inward rotation of the tibia (or shin bone) and the rolling in of the ankles, known as foot pronation. This can also contribute to increased lordosis and anterior pelvic tilt.
In a bilateral varus knee, or genu varum, the opposite is seen. The knees curve away from one another, even with the ankles touching in standing. This is also referred to as being ‘bow-legged’ (which refers to the curve of an archer’s bow) or ‘bandy-legged’. Knee varus can cause the pelvis to roll backwards into a posterior pelvic tilt with the flattening of the low back curvature. Varus knee is also sometimes referred to as knee adduction, referring to the foot and lower leg moving closer to the midline than the knee. Picture a classic cowboy stance, and that’s varus.
The tibiofemoral angle, or TFA, is used to quantify the angle between the axes of the femur — the large thigh bone — and the tibia when viewed from the front. This measurement is taken by finding the angle between a line drawn through the center of the knee joint and the ankle. Then another line is drawn from the center of the knee joint up to the front of the hip bone. If the two axes form a straight line, the measurement is zero degrees. If they form an angle, it is measured as degrees of varus or valgus, whichever is present.
Generally, “normal” TFA is defined as being in the range of six degrees of valgus, with women slightly higher than men, on average. More than 10 degrees of valgus is considered valgus malalignment while a TFA of under zero degrees is considered a varus malalignment, although there is variation in the literature regarding measurement parameters and descriptions.
The TFA has its weaknesses. It is a two-dimensional measure of a mobile, three-dimensional structure, and its accuracy can be compromised by other variables, such as an anterior pelvic tilt.
Symptoms of valgus knee
Patients with valgus knees will present with one or both knees angled in towards the other. This is often accompanied by an inward rotation of the tibia and an associated ‘rolling in’ of the ankles and feet, referred to as foot pronation or flat feet. There may be an anterior pelvic tilt, with increased lordosis of the low back.
Biomechanically, the angle at which load passes through the knee can be important. If there is excessive load placed on the outside of the knees, as happens in a valgus knee, there is an increased likelihood of degenerative changes in these parts of the knee. Excessive varus or valgus malalignment may be an independent risk factor for the development of knee arthritis.
The patella, or knee cap, functions as a fulcrum to increase the force of the quadriceps muscles, the large muscles on the front of the thigh. The patella sits in the trochlea, a groove between the two rounded ends of the femur. The tendon of the quadriceps muscles encases the patella and continues downward to attach at the top of the shin.
Knee valgus can cause problems with tracking of the patella, as the quadriceps pull the patella outward relative to the trochlear groove and patellar tendon attachment.
Knee valgus and patellar tracking issues have often been associated with pain in or around the joint between the patella and the knee. Dynamic valgus leading to patellar maltracking can be a significant factor in the development of patellofemoral pain syndrome (PFPS), a condition that causes pain around the joint between the patella and trochlea. There is strong evidence that patellofemoral arthritis is associated with both the shape of the trochlea and the alignment of the knee when viewed from the front.
Japanese researchers examining a group of 34 women with varus or valgus alignment found that subjects with valgus engaged their quadriceps more strongly when landing from a jump. In landing, subjects with valgus were not able to transfer force through to their hip joints as effectively as subjects with a varus knee alignment. This could have relevance for those working with athletes, especially those who regularly engage in explosive and high-speed jumps and landings.
A similar measurement to the TFA, the ‘Q-angle’ — or quadriceps angle — is the angle between the quadriceps muscle and the patellar tendon. It is determined by measuring the angle between a line drawn from the center of the patella upward to the front of the hip bone, and another line upward from the patellar tendon insertion on the tibia through the center of the patella. This indicates the direction of force of the quadriceps muscles on the patella and lower leg. In a valgus knee, the Q-angle could increase as the center of the shin and patella may be further medial than the front of the hip.
Q-angle has long been associated with valgus knee, although it may not be a valid or relevant measurement tool. Like the TFA, the Q-angle is a two-dimensional measurement of a three dimensional structure. It does not account for variations in pelvic shape, and may not significantly correlate with structural or dynamic knee valgus.
Brazilian researchers recently compared Q-angle and dynamic valgus of the knee on 22 women during a step-down action and found no significant correlation between the Q-angle and dynamic valgus. The British authors of a 2008 systematic review examined research regarding the validity and reliability of the Q-angle and concluded that there was a lack of consensus overall. Measurement procedures lack standardization, which may be one reason for the inconsistent findings.
Valgus knee causes
Physiologic knee valgus is very common in toddlers but is usually resolved by five or six years of age. If valgus alignment persists after early childhood, it may be a symptom of an underlying disorder or pathology. Valgus knees may present as a structural or functional condition.
Women have a higher presentation of normal, physiologic knee valgus than men, and a greater incidence of valgus during weight-bearing activities. This may occur in part because of differences in pelvic shape after puberty.
Dynamic knee valgus classically presents as valgus which is visibly apparent during weight-bearing. There is debate about whether the strength of the muscles in the hip is a factor in dynamic knee valgus in healthy individuals.
Neuromuscular conditions like paralysis or cerebral palsy, which affect the ability of the nervous system to appropriately control movement, posture, and tone, may lead to genu valgum.
Knee valgus can present secondary to ligamentous laxity, nutritional deficiencies, or bone pathologies such as osteomalacia, rickets, tumors, or arthritis. It may occur if there is an injury to the knee or leg bones during growth, in which case it will be seen only on the side of the injury. Valgus can also be present with a significant leg length discrepancy. In cases of leg length discrepancy, valgus may be observed only on one side.
Injury to supportive ligaments on the inside of the knee may lead to a valgus instability, meaning that the knee is able to deviate further medially than it should. In these cases, rehabilitative exercise and/or surgery may be indicated to restore adequate support to the medial aspect of the knee.
Obesity is often cited as a contributor to knee valgus. In some cases, obesity can create gait issues which mimic a valgus knee. Young people who are carrying extra weight may adapt gait by drawing the weight-bearing leg towards the midline while walking and increasing valgus stress on the knee.
A 2019 retrospective review published in the Journal of Pediatric Orthopedics found a significantly higher rate of obesity in children with valgus knee alignment of unknown origin, when compared to a non-valgus population. The researchers found a positive correlation between skeletal maturity and severity of valgus. They theorized that obesity in children may cause valgus stresses during skeletal development, which could influence growth and lead to more severe valgus at maturity.
If all other traumatic, pathologic or congenital causes have been ruled out, in the presence of an obvious valgus misalignment, a diagnosis of idiopathic valgus may be made.
Valgus knee treatments
There are various options available for treatment of valgus knee conditions. The appropriate treatment will depend on the reason for the valgus presentation, as well as the severity of symptoms. In many cases, a mild valgus presentation in a healthy individual will require no treatment. If the reason for the problem is related to nutrient deficiencies or disease processes, these underlying disorders will need to be addressed, along with any direct treatment for the knee itself.
The age of the individual with valgus may also influence treatment decisions since there is an ideal ‘window’ for the application of surgical techniques which aim to influence growth.
Orthotics are external devices used to change mechanics and redistribute force. Orthotics which have been used in treatment of knee valgus include foot orthotics as well as ‘unloader’ knee braces.
Braces and foot orthotics are inadequate, ineffective, and unnecessary in the treatment of genu valgum in young people. Use of a brace designed to correct valgus or varus in arthritic patients does not seem to influence biomechanics or progression of arthritis, but it may improve outcomes such as pain and the ability to complete activities of daily living.
There is very little evidence directly relating weak hip muscles with knee valgus, however exercise programs aimed at correction may still be helpful. An exercise program geared towards correction of dynamic valgus can be an effective treatment for PFPS. Exercises specifically aimed at changing the control, strength and use of the muscles around the hip have been found to be effective for correction of dynamic knee valgus.
Manual therapies like massage therapy, chiropractic, or osteopathic manual treatment are often paired up with exercise programs for issues associated with knee malalignment.
Generally, manual therapy approaches should be geared towards assisting patients with pain and mobility and supporting an active lifestyle. There is no plausible basis to believe that passive manual therapy approaches can provide any type of long-term change to the alignment or structure of any joint, especially a large, load-bearing joint such as the knee.
Very little research specifically deals with manual therapy as a treatment approach for knee misalignment issues. The available research tends to be related to treatment of arthritis symptoms sometimes associated with misalignment.
When combined with an exercise program, manual therapies show promise in the short-term management of painful symptoms associated with knee arthritis and may contribute to short term improvements in mobility.
Manual therapy may also produce a short term decrease in overall sensitivity and central nervous system pain responses. Pain is a complex phenomenon, involving both sensory input from the body, and perceptions and responses from the brain and central nervous system relate to that input. Pain management may have the added value of supporting rehabilitative exercise.
In cases of severe or progressive valgus knee misalignment in children, surgery can be a safe and effective approach to treatment. The goal of surgery is to control the final position of the joint by influencing growth prior to skeletal maturity.
An open or closed wedge osteotomy may be performed, which involves either inserting or removing a wedge of bone from the femur or tibia to affect the final position of the joint. Another method used is hemi-epiphysiodesis, which is a technique used to stop bone growth on one side temporarily or permanently. This approach is used for correction of leg length discrepancy as well as valgus or varus deformities.
Various approaches to hemi-epiphysiodesis are used to inhibit and guide growth, including stapling, or surgical application of a metal device attached across the growth plate. Patients may achieve total correction with relatively low complication rates using modern surgical techniques. When the desired alignment is achieved, the hardware is removed.
Surgery may also be considered for patients with severe arthritis associated with a valgus alignment. There is a significant incidence of need for reoperation in this patient population.
Surgical and rehabilitative downtime, and potential surgical complications, should be seriously weighed against the low possible potential of this surgery to delay total knee replacement in cases of severe arthritis.
Back to that first long-distance run, I was surprised to see how my body looked in action. That first race was as interesting mentally as it was challenging physically. At the beginning of the race, I was dismayed because I saw everyone was running pass me. Young, old, heavy, lean—every body type and description seemed faster and more athletic than I. I kept waiting to find myself at the very back of 11,000 people running that day.
As I continued, I marveled at the variation in body compositions, shapes, and especially gait patterns and biomechanics of the tired runners in front of me. Many participants had what might classically be considered ‘poor’ biomechanics. People were running with hunched shoulders, knock knees, scoliosis, no movement at all between hips and shoulders in gait. Remember, anybody I was looking at was running in front of me, so I guess they were running faster than I was!
This experience highlighted for me the importance of being active and not giving too much weight to the importance of biomechanical perfection. Seeing people (including myself), with less than perfect bodies and alignment achieve this impressive feat of athleticism and determination made me realize that in many cases, what we do with our bodies can be just as important as our physical structure and mechanics.
Feature photo: Penny Goldberg, DPT