Knock knees and vitamin D: what to know

Knock knees, also called genu valgum, describe knees that angle inward when the legs are straight. This alignment can be part of normal growth, but marked, worsening, painful, or uneven alignment deserves assessment. Low vitamin D can affect bone mineralisation and may contribute to bone shape changes in a growing child; it is only one possible explanation. A clinician may consider age, growth pattern, diet, time outdoors, limb alignment, pain, and walking pattern before deciding whether testing or imaging is appropriate.

Arrange a clinical assessment if the alignment is pronounced, increasing, present on one side, or associated with pain or tired walking. Do not start high-dose vitamin D without advice, because the right amount depends on the child and the reason for treatment. Support ordinary bone health with a balanced diet and regular age-appropriate activity. A physiotherapist can assess strength, balance, gait, and movement habits; see [Paediatric Physiotherapy](/treatments/physiotherapy-and-rehabilitation/paediatric-physiotherapy/) for related care. Severe structural alignment may need an orthopaedic discussion, including whether [Osteotomy](/treatments/reconstructive-orthopedic-surgery/osteotomy/) is relevant.

Seek prompt medical review for significant pain, swelling, fever, sudden change, refusal to walk, repeated falls, or a leg that looks noticeably different from the other. Arrange a routine appointment when knock knees persist beyond the expected growth pattern, interfere with running or stairs, or cause concern about development. Urgent assessment is appropriate after an injury if the child cannot bear weight or the leg appears deformed.

Ask whether the alignment fits the child’s age and growth stage, whether vitamin D testing is indicated, and which findings would make imaging useful. Clarify whether supplements are needed, how progress will be monitored, and whether physiotherapy could improve walking comfort or control.