**4. Radiography**

The diagnosis of patellar luxation is clinical, but radiography may help to confirm the diagnosis, showing the luxated patella in more severe cases, and can demonstrate any bony deformities that are present [6]. Mediolateral and craniocaudal radiographs enable assessment of femoral and tibial deformities (**Figure 3A, B**). Tangential views of the flexed stifle enable assessment of the femoral trochlea and its depth (**Figure 3C**). Radiographs can also delineate the morphological changes of the patella and trochlea, demonstrate secondary osteoarthritis [6, 8] and allow the prognosis of limb function.

**Figure 3.** Anteroposterior radiograph of the limbs of a dog, showing: (A) medial luxation grade IV in a 16-month-old Pekinese (left); (B) bilateral medial luxation grade III; (C) tangential view of flexed stifle showing an absent trochlea; (D) tangential view showing shallow trochlea (blue arrow), and ectopic patella in a new trochlea (red arrow).

## **5. Treatment**

Surgical management of patellar luxation in asymptomatic small-breed dogs is controversial and is not considered necessary. However, surgery is recommended early in young puppies (3–4 months) prior to irreparable contracture and in medium to large breeds prior to erosion and trochlea deformity [5]. The goal of surgical treatment is to realign the extensor apparatus to restore normal stifle biomechanics and stabilize the femoropatellar joint. Surgical procedures to stabilize patellar luxation can be divided into soft tissue reconstruction and bone reconstruction [5]. The surgical techniques include deepening of the femoral trochlea, tibial tuberosity transposition, medial soft tissue release and lateral soft tissue tightening. Other procedures, such as transplantation of the origin of the rectus femoris muscle and corrective osteotomy, can be necessary in grade III or IV patellar luxation [6, 8]. It is sometimes necessary to shorten the femur to reduce the luxation. The presence of patellar injuries does not necessarily indicate a surgical contraindication. Healing may occur, and the realignment of the quadriceps shows favourable results even in the presence of osteoarthritis. Patellectomy is rarely necessary, does not produce benefits and does not correct the alignment of the quadriceps complex [6].
