The incidence of bilateral knee valgus accounts for more than 60% of all such deformities, bilateral knee valgus for about 25%, and unilateral knee valgus and knee ectropion for the rest. Surgery is rarely required, generally less than 10%.
The causes of internal and external knee valgus are divided into two categories: physiologic and pathologic. The majority of inversions and ectropion are developmental changes that are physiologic in nature. A few are pathological, such as rickets, trauma, inflammation, congenital skeletal growth disorders, type IV mucopolysaccharidoses, tumors, poliomyelitis, and cerebral palsy, which can cause disorders in the linear arrangement of the lower extremity forces, resulting in internal and external knee deformities. In general, inversion of the knee is usually seen in the upper tibiofibula, while ectropion of the knee is usually seen in the lower femur.
Knee inversion refers to bilateral ankle joints coming together and bilateral medial knee joints not coming together in a bilateral lower limb extension position; conversely knee valgus refers to bilateral knee joints coming together and bilateral medial ankle joints not coming together. The degree is generally indicated by knee spacing and ankle spacing, with 0-5 cm being mild, 6-10 cm being moderate, and 10-15 cm or more being severe.
The presence of mild internal knee rotation is usually normal during the neonatal period and infancy. Inward rotation of the lower extremities can make the appearance of inversion more pronounced, and the presence of inversion of the knee and the tendency to fall when standing and walking are noticed by parents in children over 1 year of age. X-rays show thickening and sclerosis of the femur and tibia medial cortex, normal epiphysis, epiphyseal plate and epiphysis, and inward angulation of the middle and upper third of the tibia. There is usually a symmetrical change on both sides, with the epiphysis-hypophysis angle being less than 11° for physiologic knee inversion and greater than 11° for tibial inversion.
Physiologic knee entropion does not require special treatment, only follow-up observation. Children with rickets should be treated medically, and surgical correction should be performed when self-conscious symptoms disappear, blood calcium, phosphorus, and alkaline phosphatase have normalized, they are older, the bones are hard, and the knee spacing is more than 250 px.
In children between 1.5 and 6 years of age, the presence of mild to moderate knee valgus is a developmental knee valgus and is a normal physiological phenomenon. In children with severe knee valgus, a wobbly gait occurs, with the feet walking apart due to touching knees to avoid falls, and the child is easily fatigued. The foot valgus causes the shoe to protrude outward, and the two toes point inward, giving an “inward eight” gait. If the calf triceps and iliotibial bundle contracture, “outward” gait and pain in the calf muscle belly and front of the thigh occur. In children with severe knee valgus, the patella may be dislocated outward due to the change in direction of the quadriceps and patellar tendons. Children are obese due to reduced activity. The medial collateral ligament elongates and later leads to degenerative arthritis.
Developmental knee valgus is self-correcting in 90% of children and does not require treatment, especially in those who walk with an “inward-facing” toe, and the knee valgus is more self-correcting. If the deformity worsens during follow-up, lower limb bracing can be used to correct the deformity. To prevent foot fatigue, orthopedic shoes that are padded with longitudinal arch supports or medial wedges of the foot may also be used.
For some cases of moderate knee valgus, especially in obese children, braces and orthopedic shoes may be considered for those with ankle spacing and knee spacing over 5 cm. The purpose of applying knee inversion and valgus orthoses at night is to protect the knee joint and prevent ligament instability. Orthoses can be applied for 1-2 years.
Consider surgery for internal knee valgus with a bilateral knee spacing of 10 cm or more and external knee valgus with an internal ankle spacing of 10 cm or more. The age of surgery is postponed as much as possible until after 12 years of age.