Patella infera represents the low position of the patella in relation to the femur and the tibia. Two terminologies are used to qualify this low position of the patella: “patella baja” or “patella infera”. As the latin form is the common way to describe the high position of the patella (patella alta), it is coherent to define patella infera as the appropriate term. Its real importance lies in the biomechanical abnormality caused by the inferior situation of the patella in relation to the knee. While normal patellae are not engaged in the trochlea in extension, in cases of patella infera the patella is always in contact with the trochlea. It is most of the time a complication of a traumatic event or a previous surgery on the knee. Rarely, it is a constitutional position of the patella and it is not pathological.