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Bow Legs in Children and Adults
The knee joint is the largest and most mobile joint involved in daily activities within the human body. Due to its complex structure and a combination of rotational and sliding movements, proper biomechanical conditions are essential for its normal function. These conditions involve the coordinated action of surrounding muscles, soft tissues, and the mechanical loading of the joint. Axis misalignment leads to asymmetric loading of the joint surfaces. Given the daily strain on the knee joint due to frequent movements, this can cause overload on one compartment and accelerate the development of osteoarthritis.
Lower limb deformities are quite common in young children and are typically painless. Mild, symmetrical deformities without pain or joint stiffness usually indicate a benign condition with a good prognosis as the child grows. However, severe or asymmetrical deformities associated with pain and joint stiffness may suggest a serious underlying cause and require urgent medical attention.
Physiological Changes in Limb Axis During Growth
Axis deviations most commonly present as valgus (knock-knees) or varus (bow legs). It is important to note that changes in limb axis during childhood growth are natural developmental phenomena. Understanding how the shape of the lower limbs evolves with a child's growth is crucial. Bow legs in newborns are physiological, with the greatest curvature observed between 6–12 months of age. Between 18 and 24 months, as toddlers begin walking, the lower limbs gradually straighten. In the next stage, with proper development, the limbs transition into a valgus alignment, where the child’s knees noticeably touch. This alignment is typically observed at 3–4 years of age and corrects spontaneously by about 8 years of age.
Recognizing and Treating Bow Legs in Children
Bow legs describe a condition where the distal part of the limb deviates from the body's midline toward the center. The lower limbs form an "O" shape, with medial malleoli touching and a noticeable gap at the knee joints. This gap should not exceed 3 cm under normal circumstances. If the gap is greater than 5 cm, treatment may be required. The most common cause of this deformity is a structural deviation in the bone axis near the knee joint. Postural abnormalities caused by weakened muscles and ligaments can produce a clinical appearance similar to true structural bow legs. Bow legs are common in newborns and usually improve as the child grows. However, the condition should be monitored to ensure that it does not worsen.
Are Bow Legs in Children Normal?
Mild bow legs are not pathological. As described in the section on physiological changes in limb axis, bow legs can be present from birth, reaching their maximum curvature by the first year of life. By 2–3 years of age, the condition diminishes, transitioning into a normal axis or physiological valgus. Symmetrical bow legs during this stage of development are not pathological and are considered normal. In later stages, medical or physiotherapeutic evaluation may be necessary.
Causes of Bow Legs
Bow legs up to the age of 2 years are physiological. Beyond this age, they should not occur. Not all cases of bow legs in children require treatment. If bow legs are unilateral or pronounced, medical consultation is necessary. Determining the underlying cause of bow legs involves a thorough medical history, physical examination, and appropriate imaging studies. The deformity is usually localized to the bone near the knee, either the distal femur or the proximal tibia.
In symmetrical cases, the direct cause is often difficult to determine. Such cases are referred to as idiopathic bow legs. This condition is diagnosed by ruling out other known causes. It is often attributed to the absence of spontaneous axis correction during growth. The deformity may progress as the child grows. Some sources suggest that early walking may contribute to the condition. Other theories link it to asymmetric loading, obesity, or foot deformities. Family history, bone dysplasia, multiple osteochondromas, kidney diseases, and osteogenesis imperfecta are important factors to consider.
In asymmetrical deformities, the cause is often easier to identify. This may include improper alignment of bone fragments following a fracture, asymmetric growth plate damage due to trauma (resulting in progressive deformity), arthritis, benign bone tumors affecting growth (e.g., enchondromas or osteochondromas). In cases of asymmetrical bow legs, Blount’s disease must be excluded. This condition is caused by disrupted blood supply to part of the tibia and tends to worsen over time.
Young individuals with poor diets and insufficient vitamin D intake may develop rickets, which disrupts bone mineralization and weakens the bones. Rickets often predisposes individuals to bow legs. Nutritional rickets is now rare, but hypophosphatemic rickets, a genetic disorder affecting phosphate absorption and metabolism, can also cause bow leg deformities. Bow leg deformities in children should not cause pain. If pain occurs, further diagnostics should be conducted for internal knee joint damage, inflammatory conditions, or tumors.
Bow Legs in Young Soccer Players
It is commonly suggested that the intensity of training in young athletes, especially soccer players, is linked to the development of bow legs. However, there is insufficient scientific evidence to confirm this relationship. Nonetheless, heavy training loads during a phase of rapid growth may contribute to bow leg deformities.
How to Check for Bow Legs
A simple method to check for bow legs is to stand with legs and ankles together. If it is impossible to bring the knees together due to a gap of more than 3 cm between them, bow legs are likely present. In such cases, consulting an orthopedic specialist is recommended to determine the next steps.
Diagnosis of Bow Legs
In a medical history, questions about the child’s development, diet, and family history of similar deformities, rickets, or skeletal dysplasia are important. The physician will then perform a thorough examination of the hip, knee, and foot, assess the length and axis of the lower limbs, and evaluate tibial torsion using a goniometer.
Imaging, particularly a standing AP X-ray of the entire lower limbs (from hips to feet), is critical to assess knee joint deviation from the mechanical axis. This axis is a line connecting the center of the femoral head to the center of the talus. Normally, it passes through the middle of the intercondylar eminence, which defines the center of the knee joint in the frontal plane. Minor deviations of less than 1 cm are not considered pathological. X-rays can also determine the degree of varus deformity and its location. This examination can help identify causes such as Blount’s disease.
When and How to Treat Bow Legs
Mild bow legs in young children typically require no significant medical intervention. Observation and reevaluation within six months are sufficient. Orthopedic shoes or braces are not recommended. Vitamin D and calcium supplementation is advised.
Pathological bow legs are present when the deformity persists or worsens in children over 3 years old. Symmetrical deformities should be treated cautiously with surgery at a younger age. Mild, painless symmetrical deformities in children may benefit from observation or physiotherapy aimed at improving joint biomechanics and supporting spontaneous correction. Severe deformities may require surgical intervention, guided by radiographic findings.
If the deformity is localized around the knee and the child still has growth potential (up to 14–15 years in boys, 12–13 years in girls), growth modulation with an eight-plate device may be performed. This minimally invasive procedure allows quick recovery (most children resume normal activities within two weeks). For adolescents with little growth potential, or for deformities far from the knee joint, corrective osteotomy may be necessary.
Why Treat Bow Legs?
Bow legs lead to abnormal mechanical loading of the joint surfaces, causing medial compartment overload, meniscal damage, and early degenerative changes. Bow legs also affect the patellofemoral joint and ankle alignment, contributing to asymmetric loading and overuse injuries in the ankle and foot.
Conservative Exercises for Bow Legs
Since bow legs (genu varum) often have a bone-related cause, exercises are designed to improve the biomechanics of the knee joint and support spontaneous correction in mild deformities. Below is a set of corrective exercises for bow legs:
Standing Glute Activation: While standing, tighten the gluteal muscles and simultaneously try to bring the knees together.
Standing with a Soft Ball or Pillow: Place a soft ball or pillow between your knees while standing and perform half-squats, maintaining the position of the ball.
Stretching Adductor Magnus and Gracilis Muscles: Perform stretches in a wide stance, similar to preparing for a side split.
Seated Knee Squeezes: Sit with legs bent and squeeze a soft ball or pillow placed between your knees.
Bridge Pose with a Ball: Lie on your back with feet hip-width apart, place a soft ball between your knees, and lift your pelvis upwards while holding the ball without over-squeezing it.
Leg Circles with Support: Lying on your back, place a soft object like a small pillow or bag between your knees and make circular movements above the ground.
Supine Knee Together Pose: While lying on your back in a wide stance, bend your knees, bringing them together, with your feet positioned outward and farther apart.
Gluteus Minimus and Piriformis Stretch: Lie on your back, cross one leg over the other while bending the knee, and gently touch the floor with the bent leg while slightly twisting your hips. Ensure your back remains flat on the floor.
Related Articles:
Other potential cases in pediatric orthopedics.
References:
- White G.R., Mencio G.A.: Genu Valgum in Children: Diagnostic and Therapeutic Alternatives. „Journal of the American Academy of Orthopaedic Surgeons”, 1995
- Salenius P., Vankka E.: The development of the tibiofemoral angle in children. „The Journal of Bone and Joint Surgery”, 1975
- Kaspiris A., Zaphiropoulou C., Vasiliadis E.: Range of variation of genu valgum and association with anthropometric characteristics and physical activity: Comparison between children aged 3-9 years. „Journal of Pediatric Orthopaedics B”, 2013
- Maciałczyk-Paprocka K., Stawińska-Witoszyńska B., Kotwicki T. et al.: Prevalence of incorrect body posture in children and adolescents with overweight and obesity. „European Journal of Pediatrics”, 2017
