We are reporting six cases of congenital absence of one or both cruciate
ligaments of the knee in patients with mild proximal femoral focal
deficiency. Three patients had considerable laxity of the knee with a
positive anterior and posterior drawer sign. Three patients had an isolated
anterior drawer sign without posterior instability. Radiographic
examination showed changes in the tibial spine in all affected knees.
Arthroscopic examination showed complete absence of both cruciate ligaments
in all three patients who had the combined sagittal laxity. The three
patients with anterior laxity alone had no vestige of an anterior cruciate
ligament. None of the patients in our study had any arthroscopic or
important radiographic signs of osteoarthritis. One patient was followed
until she was sixty years old. Her case suggests that knee instability may
persist without causing osteoarthritis.