MRI after luxation of the right patella: A bone bruise is at the medial surface of the patella (axial image) and in the corresponding surface of the lateral condyle of the femur (coronal). The medial retinaculum of the patella is at least partially disrupted. Diagnosis is made through palpation of the knee, to see whether it slips inside the joint more than would normally be expected. Often, a dog owner might be told that his or her pet has "loose knee", but this is not a medical term, and it is not correct to use it interchangeably with<unk> .<unk>  cannot be present without the knee being loose, but a loose knee is not necessarily slipping out of the joint. Even with<unk> , symptoms such as intermittent limping in the rear leg might be mild or absent. Physical examination and manual manipulation are the preferred methods for diagnosis. More extreme cases can result in severe lameness. Osteoarthritis typically develops secondarily. The four recognized diagnostic grades of patellar luxation include, in order of severity: Grade I * Grade I - the patella can be manually luxated but is reduced (returns to the normal position) when released. Grade II * Grade II - the patella can be manually luxated or it can spontaneously luxate with flexion of the stifle joint. The patella remains luxated until it is manually reduced or when the animal extends the joint and derotates the tibia in the opposite direction of luxation. Grade III * Grade III - the patella remains luxated most of the time, but can be manually reduced with the stifle joint in extension. Flexion and extension of the stifle results again in luxation of the patella. Grade IV * Grade IV - the patella is permanently luxated and cannot be manually repositioned, with up to 90° of rotation of the proximal tibial plateau. The femoral trochlear groove is shallow or absent, with displacement of the quadriceps muscle group in the direction of luxation.
Luxating patella
Bipartite patella
Attenuated patella alta
Tarsal coalition
Retrocalcaneal bursitis
Sprained ankle
Bimalleolar fracture
Calcaneal spur