Patellar Realignment (Anteromedialization/Tibial Tubercle Osteotomy)

This page contains information about a common method to address recurrent dislocation of the patella (kneecap) and patellar maltracking issues.  These problems can cause chronic anterior knee pain and accelerate cartilage deterioration, often creates mechanical symptoms such as "buckling" of the knee, and place your joint at risk of further injury.  The following information is attributed to sportsmedcenter.com and can accessed by clicking on the following link: Knee Extensor Realignment – Sports Medicine and Orthopedics (sportsmedcenter.com)

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General:

Patellar malalignment is relatively common and may lead to chondromalacia at an early age with eventual osteoarthritis of the patella with the chronic overload of the lateral facet of the patella. This is exacerbated by increased body weight especially considering that patellar loading is at least 4 times body weight with activities of daily living. Patellar malalignment can be caused by several factors including a muscular imbalance of the quadriceps and is commonly exacerbated by an increased quadriceps angle (please see drawing) which mechanically increases overload of the lateral patella. The normal tibiofemoral angle contributes to overload and because of typically wider hips in women this condition is more common in women. Patellar overload is more often associated with activities which include high patellofemoral loads such as climbing, cross-country running, jumping and squatting. 

Symptoms:

Symptoms are the same as with chondromalacia but increase with increasing age and increasing patellar wear. Initially, symptoms are mild with swelling and lateral anterior knee pain. Cracking, popping or grating is palpable and may be audible with motion of the knee. As the knee becomes more arthritic in the lateral patella, stiffness occurs with sitting or reduced activities. Weather ache is common as the patella becomes more worn. Debris from the cartilage results and inflammation of the knee and increased swelling and pain.

Diagnosis:

Diagnosis is generally easily made with history and physical examination. Plain x-ray examination is very helpful especially using a skyline or merchant view which visualizes the patellar tracking viewed from the head towards the foot. When done properly, this sees the tilt and subluxation of the patella as well as significant patellar wear. CT scan or MRI may be indicated especially when meniscal or ligament pathology is suspected. These studies may help to visualize the patellar tracking in full extension because x-ray cannot see the patellar tracking with the knee completely straight. This can also be used to measure the Quadriceps Angle.  Chondromalacia and maltracking of the patella eventually lead to increased patellar arthritis. Typically, the patient experiences ups and downs in symptoms related to activity and worsen over time.

Treatment:

When conservative treatment including medial quadriceps strengthening, anti-inflammatory medication, weight reduction (if necessary), and patellar bracing have failed to decrease symptoms adequately, realignment of the extensor mechanism may be considered. This is generally performed in younger patients less than 40 years of age. This is primarily because, with arthritis present, there is less reliable improvement with extensor realignment. Multiple factors need to be considered which include: Patient age, weight, underlying arthritic changes, ligament or meniscal injuries, activity level and return to sports. Conservative measures prior to surgical intervention include medial quadriceps strengthening as outlined in my chondromalacia article.

Surgery:

Surgical intervention is considered after conservative measures have been exhausted. Lateral release arthroscopically is usually by itself, of little value and only results in significant improvement when the patella has significant lateral tilt prior to surgery and a relatively normal quadriceps angle. In an effort to lower the quadriceps angle and normalize loading on the patella, tibial tubercle transposition can be undertaken. This is generally combined with an arthroscopic lateral release which allows the patella to centralize even without dramatic tilt prior to surgery. This is generally performed with a quadriceps angle over 20° prior to surgery. To improve the safety of the procedure, it is better to leave the tibial tubercle attached distally. The tibial tubercle is undercut and bent medially using a small incision just medial to the tibial tubercle. Fixation of the tibial tubercle in this position is generally accomplished with screws which are countersunk to avoid prominence and generally the screws can be left without need for future removal. Occasionally, the patella rides much higher than it should, and the patella exits the femoral groove with full extension. In this case, distal transposition may be necessary. This is generally accomplished with 2 screws because of the added concern for solid fixation before healing has occurred. In both instances, significant bone healing generally has occurred by 6 weeks following surgery. During this, the patient remains full weight-bearing but utilizes a hinged brace locked in extension for ambulation only. To improve comfort following surgery, a femoral block is generally employed along with general anesthesia. This makes the anterior knee numb for about 24 hours following surgery allowing the procedure to be performed in an outpatient setting.