Genu Valgum in Children: Diagnostic and Therapeutic Alternatives Gregory R. White, MD, and Gregory A. Mencio, MD Abstract Genu valgum is a common orthopaedic problem in children. The vast majority femoral anteversion and compen- of cases are physiologic variants, which resolve normally. However, there are satory external tibial torsion may pathologic entities due to both focal and systemic processes in which the defor- have the appearance of valgus mity often progresses and usually requires treatment. Differentiating between malalignment of the knee when, in the two forms is facilitated by a thorough understanding of the natural history of fact, no frontal-plane deformity the development of the tibiofemoral angle in children. In this review, an approach exists. The appearance of genu val- to the evaluation and diagnosis of genu valgum is presented, and therapeutic gum in this situation is due to alternatives are discussed. malalignment in the transverse J Am Acad Orthop Surg 1995;3:275-283 (rotational) plane. Pathologic Genu Valgum Genu valgum, or knock-knee, is a and 22 months and progresses into Pathologic genu valgum is much common condition affecting the maximum valgus angulation (10 to less common than the physiologic lower limbs in children and adoles- 15 degrees) at around 3 years of age. type. However, numerous causes cents that the orthopaedist is often The normal child then has a gradual exist. Both focal and systemic called on to evaluate. As with genu resolution to physiologic knee val- processes may cause deformity that varum, physiologic forms are most gus (7 to 8 degrees) over the ensuing either is localized to a specific site common; however, pathologic years (Fig. 1). Using clinical tech- within the bone or is more general- causes, which have the propensity to niques of measurement, Staheli et ized, involving the whole bone. By progress and may require treatment, al2,3 have reported a similar pattern definition, children with pathologic do exist (Table 1). It is obviously of development. genu valgum have tibiofemoral important to distinguish between In the vast majority of children angles that are outside two standard these entities. In this review, we will with genu valgum, the tibiofemoral deviations of the mean.1-3 This mea- present an approach to the evalua- angle is within the physiologic surement varies as a function of age tion, diagnosis, and treatment of range of two standard deviations genu valgum in children. above or below the mean. They can be treated with observation and parental reassurance that the Dr. White is Chief Resident, Department of Orthopaedics and Rehabilitation, Vanderbilt Physiologic Genu Valgum “deformity” is a variant of normal University Medical Center, Nashville, Tenn. 1-3 and not a disease. Staheli has Dr. Mencio is Assistant Professor, Department Evaluating angular malalignment is suggested that such children are of Orthopaedics, Vanderbilt University School of simplified if one is familiar with the probably best described as having Medicine, Nashville. normal development of the tibio- knock-knees.2 Fat thighs, ligamen- femoral angle. Salenius and Vankka1 tous laxity, and flatfoot, which often Reprint requests: Dr. Mencio, Department of Orthopaedics and Rehabilitation, Vanderbilt have shown in a radiographic study results in toed-out habitus, can University Medical Center, Nashville, TN that the tibiofemoral angle in the accentuate the knock-kneed appear- 37232-2550. newborn is characterized by maxi- ance4 and cause physiologic genu mal lateral bowing (genu varum valgum to seem more severe. Tor- Copyright 1995 by the American Academy of angulation of 10 to 15 degrees). It sional malalignment can have a sim- Orthopaedic Surgeons. straightens between the ages of 20 ilar effect. Children with excessive Vol 3, No 5, September/October 1995 275 Genu Valgum in Children equate reduction or physeal injury gressive angular deformity.6 These Table 1 and subsequent growth arrest. In injuries should be looked for dili- Classification of Genu Valgum the proximal tibia, as in other parts gently, and families should be of the immature skeleton, Salter- informed of the potential conse- Physiologic Knock-knees Harris type III, IV, and V fractures quences to avoid subsequent Apparent genu valgum (fat pose the greatest risk of this occur- embarrassment, misunderstand- thighs, rotational deformity) rence. In contrast, several authors ing, and potential liability. Hresko Pathologic have shown that in the distal femur and Kasser6 recommend that all Idiopathic the fracture type is not predictive of patients with traumatic injury to Unresolved physiologic valgus future growth problems.5 Due to the lower extremity undergo radio- Lateral femoral hypoplasia the large cross-sectional area and graphic evaluation of the knee in Posttraumatic the convoluted anatomy of this addition to a thorough clinical eval- Malunion growth plate, damage to the physeal uation. Physeal arrest cartilage is probably extensive Another common cause of genu Metaphyseal tibial fracture despite the pattern of injury. Fur- valgum is tibia valga following Metabolic Rickets thermore, the geometry of this fracture of the proximal tibial me- Renal osteodystrophy physis may affect the ability to taphysis (Fig. 3). Since the first Neuromuscular achieve an adequate, anatomic description by Cozen7 in 1953, there Cerebral palsy reduction. have been many reports of this Paralytic conditions (e.g., It is worth mentioning that problem. Hosts of possible theories poliomyelitis) occult physeal injuries to the knee about etiology have been proposed, Infectious (e.g., osteomyelitis) may occur concomitantly with although the actual cause of the Generalized disorders more overt fractures of the metaph- abnormality remains unknown. Juvenile arthritis yseal and diaphyseal regions of the Cozen suggested that the problem Osteochondrodysplasia tibia and femur and can lead to pro- was due to asymmetric stimulation Osteogenesis imperfecta (Fig. 1). Deformity is more apt to be +20° unilateral, and treatment is often necessary. +15° Idiopathic Varus +10° Idiopathic genu valgum occurs when physiologic variants fail to +5° resolve, leading to persistent or pro- gressive deformity. Children with 0° this diagnosis are often obese and flatfooted and characterized by liga- -5° mentous laxity.4 Hypoplasia of the lateral femoral condyle and stretch- Valgus -10° ing of the medial soft-tissue struc- tures of the knee may develop in response to prolonged, excessive -15° weight-bearing through the lateral half of the joint (Fig. 2). 1 2 345 6 7891011 12 13 Age, yr Posttraumatic Trauma is probably the most Fig. 1 Graph illustrating the development of the tibiofemoral angle in children during growth, based on measurements from 1,480 examinations of 979 children. Of the lighter common cause of pathologic genu lines, the middle one represents the mean value at a given point in time, and the other two valgum. Fractures of the distal represent the deviation from the mean. The darker line represents the general trend. femur or proximal tibia can lead to (Adapted with permission from Salenius P, Vankka E: The development of the tibiofemoral angle in children. J Bone Joint Surg Am 1975;57:259-261.) valgus deformity due to either inad- 276 Journal of the American Academy of Orthopaedic Surgeons Gregory R. White, MD, and Gregory A. Mencio, MD and postulated that medial soft-tis- sue interposition was the cause of the deformity. More recently, Jordan et al13 reported on seven patients with this deformity, reviewed the major theo- ries regarding the etiology of this problem, and concluded that the most likely primary mechanism is growth stimulation of the medial portion of the proximal tibia due to fracture hyperemia. This is cur- rently the prevailing theory and is strongly supported by the findings in two case reports. Green14 re- ported a case of posttraumatic tibia valga in which the mechanism of medial overgrowth of the proximal tibia was supported by the finding of asymmetric growth-arrest lines. Zionts et al15 reported a case of tibia A B valga that showed increased radionuclide activity in the medial half of the proximal tibial growth plate on a bone scan. Metabolic Metabolic causes of pathologic Fig. 2 Idiopathic genu valgum in an obese genu valgum include the various teenager in whom physiologic valgus failed forms of rickets and renal osteodys- to resolve. Note the asymmetric involve- ment (greater on the left) and the hypoplasia trophy. Although the metabolic of the lateral femoral condyle, suggesting effects on the physis are similar in excessive lateral loading. these disorders, vitamin D–resistant and vitamin D–deficient rickets are more typically associated with varus deformity at the knee, and of the proximal tibial physis.8 Tay- renal osteodystrophy is typically lor9 attributed it to overgrowth of associated with valgus deformity.16 the tibia relative to the fibula. This difference is thought to be Salter and Best10 felt that mal- related to the pattern of mechanical union was the most important fac- loading of the physes as determined tor in the pathogenesis of the by the alignment of the knee at the valgus angulation. Houghton and time the metabolic process mani- Rooker11 experimentally produced fests itself.17 tibia valga in rabbits by sectioning Most of the disorders that are the pes anserinus and medial responsible for vitamin D–resistant C periosteum and postulated a teth- and vitamin D–deficient rickets are present from birth. Therefore, the ering