Sunrise View

A clear understanding of the anatomy and mechanics of the patellofemoral joint is critical when treating a patient that presents with a possible patellar dislocation. The alignment of the patellae should be evaluated to understand where the patellae sit in relation to the trochlea medially and laterally, as well as looking at the height of the patellae, proximal to distal. Physical exam should include assessing for a “J” sign, the patella height and patella tilt and comparing to the opposite knee. The evaluation of both physical exam and radiographic exam should include the integrity of the medial retinaculum, the height of the patella, length of the patellar tendon of the involved knee relative to the uninvolved knee. If you do not know what normal is, then it is hard to determine if there is an abnormality. The treatment of patellar dislocations can be dependent chronic verses acute problems, and if it was traumatic or non-traumatic incident.

With 40 years of experience in treating only knees, we have been able to develop a sound algorithm for treating patellar dislocations and/or malalignments that may be congenital in nature. Following a patellar dislocation, X-rays should include bilateral knees with a lateral and a merchant view (top image, above) and not a sunrise view (bottom image, above). The merchant views are with the knees bent at 45 degrees, with the muscles relaxed to allow the patellae to settle into the trochlear groove. This allows a comparison of the involved to the uninvolved patella location in the groove and to the opposite side, to see if there is any lateral displacement. The lateral views are with 60 degrees of flexion, and with the quad contracted. The patellar tendon length is measured bilaterally, on the 60-degree flexion view. The average patellar length for males is 50 mm and for females is 45 mm. We can also measure the height of the patellae by measuring from the inferior tip of the patella chondral surface to the level of Blumensaat’s line. With the quad contracted, we can evaluate the height of the patella in relation to the trochlear groove.

MRI scan can further evaluate the status of the medial retinaculum, which is seen on the axial view, and we look for any chondral defects of the patellofemoral joint.

Treatment is dependent on the physical exam, X-ray measurements and MRI results. There are three options for patellar realignments:

  1. Medial Imbrication with Lateral Release(MI/LR)
    1. Usually done with acute dislocation and normal anatomy
    2. Soft tissue correction only and no bony changes
    3. Release the lateral retinaculum and tighten medially to realign patella
    4. Patient wears an immobilizer when walking the first 1-2 weeks depending on quad control
    5. Bedrest with CPM with exercises of taking to 120 on CPM, SLR, 3x/day during the first week to minimize swelling and pain
  2. Elmslie Trillat Procedure (Trillat)
    1. Usually done with acute dislocation but patella sitting laterally but normal patellar tendon length
    2. Tibial tubercle is cut and moved medially (pivot)
    3. Fixed with plate and screws
    4. Will also do a MI/LR as above
    5. Bedrest with CPM with exercises of taking to 120 on CPM and SLR 3x/day.
  3. Distalization Procedure
    1. Usually done with acute/chronic dislocation with patella alta
    2. Tibial tubercle is cut and moved distally and medially (if indicated)
    3. Fixed with plate and screws
    4. Will also do the MI/LR as above
    5. Patient wears the immobilizer when walking the first 3-4 weeks
    6. Flexion limited to 90 degrees max (or lower based on tolerance) for CPM exercise 3x/day
    7. Will also do quad sets but no SLR as an exercise 3x/day. Assist lifting the leg in and out of CPM during first week of bedrest.

The purpose of bedrest in the first week with the use of CPM is more about controlling the effusion in the knee joint which allows us to be more aggressive starting week two (refer to our Blog on CPM use during first week). Our outcomes show the IKDC 2 years post op is 84 out of 100. By one week, patients have full symmetrical extension and by 4-6 weeks, they demonstrate symmetrical flexion. The mean strength at three months postop show 70% of 110 patients got greater than or equal to 90% of their pre-op strength, and 12% of those patients had strength between 80-89%.