Medial Patellar Luxation

What is medial patellar luxation?

  •  The patella (kneecap) normally rides in a groove called the trochlea at the end of the femur bone (Figure 1). When the patella luxates or moves out of the groove, the knee joint cannot flex properly (Figure 2).
  •  Patellar luxation is usually caused by a conformational abnormality at the level of the hip joint and results in abnormal forces that act on the kneecap causing it to ride outside the groove. In young animals, the groove becomes very shallow and the attachment of the patellar ligament is often malpositioned on the tibia (shin bone). The kneecap most often luxates to the inner aspect of the knee joint and is called medial patellar luxation.


Clinical Signs:

  •  Lameness/Pain
  •  Intermittent skipping
  •  Stiffness of the affected leg
  •  Combination of the above


  •  In most cases, a series of three to four surgical steps are taken to properly align the patella.
  •  If the groove is shallow or misshapen, it is surgically deepened to allow the patella to sit deeper within the femur. Replacement cartilage (fiibrocartilage) will gradually fill in the recontoured portion of bone (Figure 3).
  •  The attachment of the patellar ligament to the tibial crest is often surgically repositioned to the side opposite the luxation. It is then secured in place with one or two metal pins (Figure 4).
  •  The joint capsule and surrounding muscle along the side of the patella are often stretched during a luxation. These tissues are sutured or tightened on the opposite the side of the luxation to provide additional support and prevent abnormal movement of the patella.
  •  Occasionally, the joint capsule on the side of the luxation is ‘released’ to reduce tension.



  •  Pets are often beginning to touch the toes to the ground by 10-14 days. Some take a bit longer depending upon the severity of the luxation.
  •  Most pets are using the operated limb well by 6-8 weeks.


  •  Approximately 90% of our patients will return to normal function of the limb.
  •  Surgery is designed to address the luxating patella, but cannot reverse arthritic changes that are already present in the knee joint. Patients with arthritic knees may have some stiffness after rest or may become lame after heavy exercise.
  •  Some patients with a severe luxation are at risk for reluxating after surgery. Fortunately, this is not common for most pets.

Potential Complications:

  •  Anesthetic related complications can occur with any procedure. Close monitoring of our patients throughout the surgery and recovery period minimizes these complications.
  •  As with any surgical procedure, infection is always a concern. Keeping the surgical site clean and preventing pets from licking the incision is of paramount importance.
  •  Occasionally, the pin(s) used to secure the transposed portion of the shin bone can shift or back out. Once the bone is healed (at approximately 8 weeks), the pin(s) is no longer needed and are removed if they migrate.
  •  A fluid swelling (seroma) may occur over the pins.
  •  Excessive activity during the first 6-8 weeks can result in a breakdown of the repair requiring additional surgery.

Post-operative Instructions MPL (Medial Patellar Luxation)

1.  Keep your pet restricted from excessive activity for the next 6 weeks.  No running, jumping or rough play with other pets during this time.  No unsupervised time outside for the first 6 weeks.

2. Utilize the E-collar or inflatable collar to prevent licking and/or chewing of the incision.

3.  Applying a cold pack to the knee (5-10 minutes daily) will help to reduce inflammation.

4.  Short, slow, leashed walks (5 minutes) twice daily are encouraged.

5.  Medications have been dispensed.  Please follow label directions.

6.  Recheck appointments are necessary at the following times:
  a) 10-14 days for suture removal.
  b) 4 weeks for limb usage evaluation.
  c) 6 weeks for limb usage evaluation.

A rehabilitation protocol has been attached for specific exercises at certain points along his/her recovery.

Please call if you have any questions or concerns. (303)761-7063.


Post Operative Rehabilitation Protocol for Patella Subluxation Surgery

Week 1:

  1. Ice pack over operated knee for 5 minutes 2 times per day for 3 days, especially after exercise. (package of frozen peas or corn wrapped in a damp towel).  Apply a warm compress to the incision for 5 minutes twice daily beginning on day 4 after surgery.  Continue warm comrpesses for 3 days. 
  2.  Massage the thigh muscles for 5 minutes daily.
  3.  Slow leash walks (5 minutes) 2 times per day.  No stair climbing is allowed. 

Weeks 2 & 3:

(Click to see video)

Video provided by: Dennis Caywood DVM, MS, DACVS, CCRT
Senior Veterinary Specialist- Surgery/Rehabilitation

  1.  Begin range of motion exercises (flexion and extension) and ice if swelling is present.  Our staff will show you how to perform these exercises. 
  2. Slow leashed walks (10 minutes) 2 times/day on flat, nonslippery surfaces.
  3. Continue massage.

Weeks 4 & 5:

  1. Slow leash walks 15-20 minutes two to three times per day on flat surfaces..
  2. Sit/stand 10 repetitions 2 times per day
  3. While walking with your dog, gently nudge him/her sideways.
  4. Figure 8 walks or circling to left and right 10 times.
  5. If your pet is doing well, "dance" with him/her.  Hold up the front legs to encourage him/her to walk on the hind legs.

Weeks 6, 7 & 8:

  1.  Leash walk 30-40 minutes, including inclines, hills, ramps.
  2. Stair walks slowly 5 flights twice a day.
  3.  Tug-of-war.

Weeks 9 & 10:

  1. Faster walks on leash 30-40 minutes.
  2. Runs on leash straight only, no turns.

Weeks 11 & 12:

  1. Turns on leash at a run.
  2. Gradual return to full activity at the end of 12 weeks.
  3.  Avoid extreme activity such as chasing a ball or playing Frisbee to reduce the chances of further injury.