Is the ACL damaged?
No, despite what looked like a flake avulsion from the tibial spine, the ACL is intact.
What does the flake of bone seen on the plain film represent?
It is a fragment of bone attached to a much larger chondral fragment with a large osteochondral defect of the lateral femoral condyle
Is there a predisposition to patella dislocation in this case?
Yes, the trochlear groove is shallow.
What other significant injury has occurred - take a look at the patellofemoral compartment.
There has been a patella dislocation - there is marked bone oedema on the medial aspect of the patella and the lateral femoral condyle.
Large osteochondral defect of the femoral condyle and medial patella with loose bodies in the joint. Kissing-contusions secondary to patella dislocation and a shallow trochlear groove. Large joint effusion.