Congenital lateral dislocation of the patella.

Congenital lateral dislocation of the patella is a rare condition caused by displacement of the extensor mechanism of the knee, which occurs before or shortly after birth (Malkin 1932). The patella is small and cannot be replaced in its normal position except by operation. This type of dislocation differs from recurrent or habitual dislocation of the patella, which occurs during childhood or adolescence and may be caused by congenital anomalies such as failure of the development of the lateral femoral condyle (Smillie 1951) or an abnormal attachment of the iliotibial tract (Ober 1939, Jeifreys 1963). Congenital dislocation may have the same etiology (Malkin 1932, Ober 1939) but must be differentiated from recurrent dislocation from congenital causes. When the patella and extensor apparatus are permanently displaced laterally, full active