Treatment:

The cranial cruciate ligament (CrCL) is a fibrous connective tissue that connects the femur to the tibia, and affords stability to the stifle joint.  After Bonnie's CrCL ruptured, increased joint laxity led to increased contact (excessive compressive forces) between the femur and tibia, resulting in changes to the layers of the articular cartilage.  Critical to cessation of further degenerative joint changes is stabilization of the joint.  

Conservative (medical) management of CrCL rupture involves confined rest for 4-8 weeks, complemented by analgesic/anti-inflammatory therapy.  This approach allows for compensatory changes in the joint and its capsule (fibrosis, increased joint fluid) to provide for an increased stability.  The main drawback to medical management is that it allows for degenerative changes to the joint to progress.  Also, medical management increases the chances of similar problems in the other stifle joint within 12-18 months, as an increased weight load is placed on the other leg.  

Therefore, surgical resolution of the instability, via intracapsular repair, is warranted.  Bonnie is a good candidate for this type of surgery, because this is an acute rupture.  In other words, a lack of radiographic signs of degenerative joint disease suggests that her tissues are capable of supporting a healthy joint.

The over-the-top technique is chosen for Bonnie's surgery.  This techique consists  of removing a portion of the patella without splitting the patella or entering the joint.  A strip of fascia, corresponding in width to the medial one-third of the patellar ligament and incorporating the wedge of patella, is dissected free.  The stifle is inspected and debrided after a medial arthrotomy is performed.  The patella is displaced laterally to expose the fabella.  The free end of the graft is passed through the femoral condyles and is attached to the lateral femoral condyle with stainless steel sutures.  The correct tension should be applied to the graft until cranial drawer motion is eliminated prior to suturing and closure of the joint.  

Postoperative management consists of immobilization with a cast, lateral splint, or soft-padded bandage with cage rest for 2 to 8 weeks.  A gradual increase in activity occurs over one to two months.  The ideal postoperative physical therapy program should maintain thigh muscle strength, joint stability, and range of motion, and promote early return to function and diminish degenerative joint disease.  Swimming is the ideal exercise to maintain joint function without the added stress of a weight-bearing exercise.   Pain management will begin during surgery with the use of an opioid(Morphine)  epidural.  The benefits of this protocol allow for prolonged local analgesia  postoperatively with minimal added risk of sedation seen with parenterally administered opioids.   Bonnie will be discharged with oral analgesic/anti-inflammatory therapy consisting  of phenylbutazone(200-600 mg/day in 2 or 3 doses for 4 days followed by 100 mg/day for 10 days).  
 
Bonnie's  prognosis is good to excellent following the surgical intervention.  However,  careful attention to a weight loss program and regular exercise should help prevent possible damage to the right stifle and further degenerative changes  to the injured left stifle.