Patellofemoral joint stabilization
Damir Hudetz
University hospital Sveti Duh, Zagreb
Specialty hospital St.Catherine, Zabok
Patellofemoral joint is of utmost importance for the function of knee flexion and extension. Tracking in the patellofemoral joint is commonly affected with wide range of problems ranging from mild lateral maltracking and tilt to instability with subluxation and dislocation. Patients with instability have relatively high probability of recurrence. Each episode of dislocation or subluxation contributes to a number of significant problems, including persistent knee pain, functional limitations, decreased athletic performance and arthritic degeneration of the patellofemoral joint. Surgical treatment plays major role in the treatment in cases of recurrent dislocation whereas systemic physical therapy has important role in patients with mild lateral maltracking. Patellofemoral instability with dislocation has usually lateral direction. The incidence of this injury has been shown to be around 6 per 100000 with the highest incidence occurring in the 2 nd decade of life.
Tracking and stability of the patellofemoral joint is influenced by osseous anatomy of patella and trochlea. Any dysplastic changes of patella and trochlea can lead to instability. The shape of trochlea closely matches the articular shape of the patella providing restraint for excessive lateral movement of the patella. Patellofemoral dysplasia has been classified by Dejour et al. Patella alta with increased length of the patellar tendon contributes to patellar instability.
Soft tissue structures important for the stability of the patellofemoral joint include lateral retinaculum, iliotibial band and vastus lateralis muscle on the lateral side and medial retinaculum, medial patellofemoral ligament and vastus medialis muscle on the medial side. Weakness or disruption of the medial stabilizers can lead to lateral instability especially at flexion angles between
0-30 degrees. Tightness or excessive force by the lateral stabilizers like lateral patellar retinaculum or iliotibial band with its fibers can produce abnormal patellar tilt and maltracking. Dynamic stabilizers both on medial (vastus medialis obliqus) and lateral side (vastus lateralis muscle) contribute to stability.
Lower extremity malalignment influences patellofemoral joint stability. Increased femoral anteversion with internal rotation of the femoral condyle, external tibial torsion and valgus femoral alignement contribute to femoropatellar maltracking.
Femoropatellar stabilization treatment depends on clinical presentation. The patient may present with instability without pain, pain without instability or instability and pain as a consequence of all anatomical modalities and trauma. Usually first time dislocations are treated conservatively.
Recurrent dislocations are treated with surgical therapy adjusted to specific condition. In recent years after introduction in 1994 reconstruction of the MPFL has gained popularity with excellent results. This treatment can be combined with different osteotomy type in order to address

underlying osseous pathology. Tibial tubercle osteotomies in various planes, corrective osteotomies of the femoral axis in terms of varisation and derotation or trochleaplasty can successfully stabilize patella with respect to trochlea and reduce pain.