It is located cranially to the joint and sits in the trochlear groove of the femur.

A kneecap in an "alta" position sits above the "trochlear groove" and therefore is less stable.

This ligament acts to keep the patella within the trochlear groove during flexion and extension.

Arthroscopy Use a suprapatella portal to watch patella centre in trochlear groove betw. 30-60deg.

The spiralling nature of the trochlear groove results in the varying transverse axes of the elbow joint.

In normal flexion and extension of the stifle joint the patella glides in the trochlear groove.

The femoral trochlear groove is shallow or absent, with displacement of the quadriceps muscle group in the direction of luxation.

Another cause that patellar dislocation can occur is when the trochlear groove that has been completely flattened is defined as trochlear dysplasia.

As the knee flexes ('bends'), the kneecap moves towards the inner aspect (medial) of the knee, then engages with the trochlea at about 30 degrees of flexion, then runs centrally in the trochlear groove during the rest of bending.

Patellar subluxation can be caused by osseous abnormalities, such as incorrect articulation of the femoral groove with the patella, trochlear dysplasia, or patella alta, which is a distance of greater than 20 mm between the tibial tubercle and the trochlear groove.