When a child with bowlegs stands with his or her feet together, toes pointed straight ahead, and the knees do not touch, he or she has bow-legs. The medical term is “genu varum”. It may come from the thighbone (femur), shinbone (tibia) or both
When a child with knock-knees stands with his or her legs together, feet pointed straight ahead, and the knees touch but their ankles do not, he or she has knock-knees. The medical term is “genu valgum”. It too may come from the thighbone, shinbone or both.
A newborn child is normally born with about 10 to 15 degrees of varus angulation. The angulation gradually decreases in the second year of life and reaches 0 degrees by 2 years age. This normal varus angle which persists till the age of 2 years is called “Physiological” bowlegs. Thereafter the knee start growing into valgus and reach a peak valgus angle of about 10 degrees by the age of 4 years. This normal valgus angle is called “Physiological” knock-knees. After the age of 4 years, the valgus decreases to adult angle of about 6 degrees valgus by the age of 8 years.
Any deformity which fails to follow the above normal pattern is deemed to be abnormal.
Deformity occurring due to underlying metabolic bone disease
The first step in the treatment of bowlegs and knockknees is establishing the diagnosis which is done on the basis of clinical examination, blood investigations (blood levels of Calcium, Vitamin D,etc.) , X-rays and in special situations advanced imaging like MRI, CT-scan, etc. In most of the cases, bowlegs/ knock-knees is normal (physiological) in which case parents need to be reassured that the deformity will automatically resolve with age. In cases where the deformity is abnormal (pathological), treatment may consist of:
Surgical treatment: is needed in most cases of pathological (abnormal) bowlegs and knock-knees. Surgical treatment is broadly of two types:
Growth modulation (guided growth) with eight plates: The eight plate is a metallic device which is implanted in the growing bone straddling the growth plate. The eight plate functions by guiding the bone growth in such a way that the deformity corrects with growth. This technique is an ideal modality for younger children with healthy growth plates with sufficient growth remaining.
Corrective Osteotomy: Osteotomy is a surgical procedure in which the deformed bone is cut at the level of deformity, the deformity is corrected and the bone is fixed in the corrected position with implants to maintain correction. It is a larger surgical undertaking than a growth plate and needs to be performed in older children or in children with damaged growth plates in whom the potential for remaining growth is limited.