Before my mother-in-law had both knees replaced, she walked with a distinctive gait, rocking her body back and forth to accommodate her bowed, stiff and painful, arthritic knees. After a bilateral knee replacement surgery, she was almost unrecognizable when seen from a distance. Her legs were straight, her knees moved properly, and she walked with an unremarkable gait pattern. She said it was the first time in her life that her legs were not bowed.
Varus knee, also known as genu varum, occurs when the knees bow away from each other in a standing position. This can lead to foot supination on the affected side and is sometimes associated with a flattening of the low back curve known as lordosis and a posterior pelvic tilt. In massage school, we used the mnemonic “Pirates drink rum, and they’re bowlegged” to help remember the difference between this and valgus knee.
Genu varum is normal in infants and toddlers under age two. After this stage, if it presents on one side or comes on suddenly, there may be an underlying problem that could require treatment.
Difference between valgus and varus knee
In bilateral knee varus, 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 flattening of the low back lordosis. 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.
In a bilateral valgus knee, also known as genu valgum, the opposite is seen. 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 rolling in of the ankles, known as foot pronation. This can contribute to an increased lordosis and anterior pelvic tilt.
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 determining the angle between a line drawn through the center of the knee joint down through the center of the ankle, and another 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. Over ten 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 a curve in the thigh bone.
Symptoms of varus knee
A patient with knee varus will present with a TFA of less than zero degrees. In simple terms, as soon as the knee starts to bow outwards visibly, it is considered a varus malalignment. The most obvious symptom of genu varum is visible bowing out of the knee. The ankles may touch in standing with the knees apart. This may be associated with outward rotation of the tibia, and rolling out of the feet, also known as supination or eversion. This may also present with a flattening of the low back and a posterior pelvic tilt.
Biomechanically, the angle at which load passes through the knee can be important. Excessive varus or valgus malalignment may be an independent risk factor for the development of knee arthritis. Varus alignment increases the load on the inner aspect of the knee joint. In patients already experiencing arthritis, varus malalignment increases the likelihood of degenerative changes in the medial aspect of the knee.
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, via the patellar tendon.
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 varus knee the Q-angle will likely decrease, as the center of the shin and patella may be further lateral relative to the front of the hip. The large quadriceps muscle will exert more of a vertical pull on the patella in this alignment than they would in a normal alignment, which is slightly valgus.
Knee varus may present an increased likelihood of osteoarthritis in the medial aspect of the joint between the patella and femur, possibly as a result of increased muscle tension and loading through the medial aspect of the patella.
Japanese researchers examining a group of 34 women with varus or valgus knee alignment found that subjects with varus engaged their quadriceps less strongly when landing from a jump than those with valgus. In landing, subjects with a varus knee alignment were able to transfer force through to their hip joints more effectively than subjects with valgus alignment. This could have relevance for those working with athletes, especially those who regularly engage in explosive and high-speed jumps and landings.
Varus knee causes
Knee varus is normal before age two, but if it persists after this age it may be a symptom of an underlying disorder or pathology. Idiopathic knee varus occurs when varus alignment persists past two years of age without another known cause.
Knee varus can present secondary to nutritional deficiencies, or disorders affecting bone growth, such as Blount disease, achondroplasia (a common cause of dwarfism), Paget’s disease, tumours, infections, or arthritis. Calcium and vitamin D deficiencies may lead to osteomalacia and rickets, which may cause varus.
Varus alignment 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. Varus can also present in association with a significant leg length discrepancy. In cases of leg length discrepancy, varus may be observed only on one side.
Injury to the supportive ligaments of the knee may lead to a varus instability, meaning that the knee is able to deviate further laterally than it should. In these cases, rehabilitative exercise and/or surgery may be indicated to restore adequate support to the outer aspect of the knee.
Varus can be both a contributor to and a result of osteoarthritis in the knee. Loss of joint space and degenerative changes caused by arthritis can increase existing alignment issues. Varus malalignment may increase the rate at which knee arthritis progresses.
Varus knee treatments
There are various options available for treatment of knee varus. The appropriate treatment will depend on the reason for the varus presentation, as well as the severity of symptoms. The age of the patient may also influence treatment decisions, as there is an ideal ‘window’ for the application of surgical techniques aiming to influence growth.
In many cases, a mild varus knee alignment 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 need to be addressed along with any direct treatment of the knee itself.
Orthotics are external devices used to alter mechanics and redistribute force. Orthotics that have been used in treatment of knee varus include laterally wedged foot orthotics as well as ‘valgus unloader’ knee braces, which may be used in conjunction with each other.
Valgus unloader braces are often used for the management of medial knee arthritis, frequently associated with varus knee alignment. Unloader braces are designed to ‘open up’ the medial aspect of the knee joint during weight-bearing. They do this by inducing a valgus force into the joint and transferring load through the brace itself, and to the other side of the knee joint.
Valgus unloaders may affect mechanics and change load distribution during gait, however the effect may be so small as to be clinically irrelevant. This minimal mechanical effect does not appear to be associated with long term improvement in pain and functional activity outcomes, although bracing may offer beneficial support in short-term rehab. There is very little quality evidence to inform recommendations regarding use of knee braces in varus arthritis, but the available evidence fails to support their use.
Lateral wedge orthotics aim to indirectly correct the angle at the knee by changing the position of the ankle. By raising up the outer side of the foot, the ankle may be brought out of supination, lessening external rotation of the tibia and associated varus knee positioning.
Although in theory this makes sense, orthotics have not been found to provide long-term benefits to patients experiencing medial knee osteoarthritis. When compared to a neutral insole added to the shoe, they provide no additional benefit in pain or functional outcomes. There is a lack of any quality research support for the use of these devices.
Generally speaking, varus knees are more likely to result from conditions which affect the structure of the leg, such as growth disorders or arthritis. Functional deficits like weakness or lack of muscle control have more commonly been associated with a valgus knee presentation. Since slight valgus is the normal orientation of the knee, it is also the direction in which a normally aligned knee will collapse in weight bearing, without proper muscular support and control.
Individuals with a non-pathological varus knee alignment should engage in an active lifestyle. Although a varus knee alignment may slightly increase the chance of eventual arthritis development, there are many other factors involved in the development of arthritis. Overall mental and physical health benefits of regular exercise are significant and numerous and may help to offset any increased risk of arthritis presented by malalignment.
Mechanical alignment may be a consideration when engaging in activities such as long-distance running or weight lifting, as these activities involve higher loads and repetitive impacts. It is important when engaging in endurance sports or heavy lifting to ensure a gradual build up in training, in order to give body structures the opportunity to adapt, and decrease risk of injury. This could be even more important in situations where alignment impairs the ability of the joint to efficiently disperse impact, increasing stress in isolated regions of the knee joint.
Individuals who engage in low to moderate amounts of running are not at higher risk of developing knee osteoarthritis, and there is no conclusive link between higher volumes of running and the development of knee osteoarthritis. This means that individuals with varus knees should be able to engage in a moderate running program without any concern of significantly increasing their eventual arthritis risk.
Corrective exercise may have some potential in patients with varus knee arthritis to effect small changes in weight bearing alignment, although this does not correlate to a change in alignment during gait. Individualized exercise programs aimed at affecting control of the leg muscles can be safe even in populations with severe knee osteoarthritis, and may offer additional benefits of pain control and improved overall conditioning.
Physical therapy approaches used to address knee varus may include use of orthotics, braces, corrective exercise programs, and manual therapy approaches. The goals of treatment will depend on the reason for the varus presentation as well as the personal goals and needs of the patient.
In pediatric cases of idiopathic knee varus, exercises may be used in conjunction with manual therapy approaches to positively influence gait patterns and muscle development.
In patients with knee varus and osteoarthritis, the general goal of physical therapy will be to support active living and to assist patients in maintaining mobility and managing pain. In addition to guiding patients in exercise programs which support their goals, manual therapy approaches like massage therapy may be used to assist with mobility and pain control.
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 central nervous system perceptions and responses related to that input. Pain management has the added value of supporting rehabilitative exercise.
In cases of severe or progressive varus 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, either 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 varus alignment. Varying surgical approaches may have different levels of success, with some showing good long-term benefit and others only providing short-term improvement. These surgeries may also be performed with a goal of delaying or eliminating the need for an eventual total knee replacement.
In the most severe cases of osteoarthritis, a total knee replacement may be performed, and any valgus or varus malalignment will be corrected.
Knee varus may present specific mechanical challenges to the body, but in most cases will not require intervention. More severe presentations and possible arthritic complications have good treatment options available to manage pain and dysfunction, and correct structural defects if necessary or appropriate. Varus is associated with an increased likelihood of arthritic changes in the knee, but a diagnosis of varus knee does not guarantee the eventual development of arthritis, nor is arthritis always associated with pain.
My mother-in-law sailed through both of her knee replacement surgeries like a champion, and recovered very quickly. She told us she could vividly remember walking out of the operating room after the first surgery, although the surgeon and other staff assured her this hadn’t been the case! Maybe she was just that excited to have a new, mobile and properly aligned pair of knees to get her around.
These days, my mother-in-law is an energetic and healthy individual, no longer plagued by pain and loss of mobility. After struggling with disability and knee pain for so many years, she is now able to enjoy a full and active retirement.