Patella alta, or a high riding patella, can be a congenital finding, or if acute and associated with an inability to straight leg raise, more likely due to a complete patella tendon tear.  

Many debate the 'more' correct terminology, between a patella ligament and a patella tendon.  The patella bone is a sesamoid bone, so many will deem the patella tendon 'a tendon', as it is a continuation of the quadriceps muscle group and quadriceps tendon, to then insert on to the tibial tubercle.