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Knock Knees / Genu Valgum
Definition: An augmentation in the normal tibiofemoral angle results in genu valgum.
Causes: Genu valgum is most manifest in females due to their wider pelvis and shorter femurs. Other causes of genu valgum include rickets in children and osteomalacia in adults. Mild genu valgum can be present in children aged two to five however, this has a tendency to rectify itself as the child enters adulthood. Some cases of genu valgum are congenital and can be aggravated by obesity, and arthritic knees where the joint is deformed.
Examination: Genu valgum is not necessarily pathological. Knock-knees are a cause for concern when symptoms arise as a result of their presence, or if they are secondary to some underlying bone pathology. A patient suffering from advanced genu valgum will be unable to maintain the medial border of their feet together whilst simultaneously straightening their legs.
Orthopaedic test for the diagnosis of genu valgum:
A line is drawn for the anterior superior iliac spine through the centre of the patella on the same leg. A second line is drawn from the centre of the patella to the centre of the tibial tubercule. The angle formed by the intersection of these two lines is called the Q angle and should be no greater than 22° in females and 18° in males with the knee extended.