Knock Knees and Flat Feet in Children Dr Gillian Wilson Knock Knees / Genu Valgum • Legs are bowed inwards in the standing position. Bowing occurs at or around the knee. On standing with knees together, the feet are far apart. Normal Development • Most children are “bowlegged” from birth until around 3 years old, then become “knock kneed” until age 4 to 5, and straighten towards adult alignment by age 6 to 7. Investigations 1 • Measurement of intermalleolar distance. i.e Distance between two malleoli when the knees are gently touching with legs in adduction. • Up to 3 and a half inches (9 centimeters) with child lying down is acceptable. • 75% of children aged 2 - 4 years have some degree of intermalleolar separation. Investigations2 • Intermalleolar separation under 3 inches is normal at any age. • Periodic observation and measurement if less than 3.5 inches. • If > 3.5 inches, need AP X-Ray with both legs on same film for knee deformity, hip and ankle joints and view of both long bones. Indicators of Serious Disease • Pronounced asymmetry • Short stature • Other skeletal abnormalities • Intermalleolar separation greater than 3.5 inches Aetiology • Developmental • Miscellaneous syndromes e.g Rickets (Alk Phos raised, with x-ray changes) • Rare Genetic disorders e.g Cohen Syndrome • Nutritional conditions e.g Vitamin C deficiency • Autoimmune e.g RA • Degenerative e.g OA When to refer • Age > 7 with knock knee • Unilateral problem i.e Asymmetry of legs • Intermalleolar distance > 3.5 inches (9 cms) • Associated symptoms e.g Pain, Limp Treatment • No evidence that shoe modification, splints, or exercises affect condition • No evidence to justify surgical intervention under 6 inches of intermalleolar separation. • Surgical options: Medial epiphyseal stapling at 10 to 11 years Corrective osteotomy at maturity. Flat Feet / Pes Planus • Arch of the foot is low. Medial arch is lost. There may be some valgus and eversion deformity of the foot. Normal Development • Flat feet are normal when learning to walk. • Medial arch does not develop until 2nd / 3rd year of life. • Normal arch functions as a shock absorber. Investigation • Ask patient to stand on tiptoes. • If medial arch restores itself when standing on tiptoe or when foot is unloaded, no action is needed. Presentations • 2 Groups: – Pain free feet with normal mobility and muscle power. – Painful, stiff, hypermobile feet with abnormal muscle power i.e weak or spastic feet. Causes of Flat Feet • Loose - ligamented flat foot: – Commonest type. – Always bilateral. – Arch looks normal when non weight bearing / standing on tip toe. – Laxity can often be demonstrated in other joints. Rare Causes of Flat Feet • Rocker bottom foot : Congenital vertical talus. • Coalition Syndrome: Peroneal spastic flat foot. • In both, subtalar joint movement is limited. • In peroneal spastic flat foot, attempting to invert hind foot produces painful spasm of peroneal muscles. Rare Causes of Flat Feet • May be part of a more generalized condition – Severe joint laxity – Cerebral Palsy – Peroneal spastic flat foot – Downs Syndrome Treatment • No proven benefit from insoles, shoe modification, foot exercises. • Spasmodic type : – Hindfoot fusion for pain relief. – Subtalar arthrodesis corrects deformity. Summary • Knock Knees: – less than 3 inches intermalleolar separation is normal at any age. – Refer if age >7. Asymmetry, intermalleolar distance > 3.5 inches, short stature, pain or limp. – Remember normal developmental stages. Summary • Flat Feet: – Test by standing patient on tip toes. – Refer if painful, stiff, hypermobile with abnormal muscle power. – Waiting time for Orthopaedic OPA at Birmingham Childrens Hospital is less than 4 weeks, but > 13 weeks for physiotherapy.
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