Patellofemoral joint is the joint that is between patella and femoral trochlea. Quadriceps, along with the patellar tendon, forms the extensor mechanism of the knee. For joint stability, while patellar tendon, medial-lateral retinaculum, trochlear groove are the passive stabilizers, quadriceps is the active stabilizer. Between quadriceps muscle contracture vector and patellar tendon axis, there is a 10-degree valgus vector. This angle is called q angle and it is important for patellofemoral pathologies.
Acute Patella Dislocation
Etiopathogenesis: It is commonly seen during childhood and adolescence. It is not seen in normal knees with the exception of trauma. Commonly, dislocation occur because of rotational trauma due to a blow to lateral knee.
Clinical Status: There is severe pain and decreased range of motion. In general, patella is relocated spontaneously. Rarely, for patients who are admitted to hospital with a dislocated patella, reduction is performed by pushing patella medially while knee is in extension.
Diagnosis: Diagnosis is made with an AP x-ray. However, it is hard to determine the pathology in relocated knee. That’s why definitive diagnosis is made with MRI. MRI is important as it shows medial retinaculum tear, trochlear dysplasia and possible osteochondral damage.
Treatment: The approach for the first dislocation is knee immobilization in extended position, so that medial retinaculum is healed; then, rehabilitation by quadriceps strengthening with using patella stabilizing knee pad. For athletes, additional osteochondral injuries or patients with high risk of recurring dislocation due to underlying pathologies, surgery may be performed after the first dislocation. Surgical approaches include medial retinaculum repair, arthroscopic or open lateral release and relocation of vastus medialis obliquus medially and distally.
Habitual Patella Dislocation
Patella is at its proper location during extension, but it is dislocated laterally during flexion. Vastus lateralis fibrosis, iliotibial band anomalies are thought to be the etiology. During flexion and extension motion, patella dislocates laterally by passing over trochlea after 30-40 degree of flexion. While painless during the childhood, it may lead to arthrosis, if it is not treated, in adulthood.
Recurring Patella Dislocation
Patella is at its normal position during flexion and extension movement. It is more commonly seen in adolescent females. In general, they admit to hospital with acute dislocation for multiple times. At advanced stages, patella dislocates and relocates easier. Trochlear and patellar dysplasia, patella alta, vastus medialis insufficiency and vastus lateralis fibrosis can be seen among the causes. Osteochondral injuries may be observed during acute dislocation. Q angle is high in these patients.
Treatment: It is decided according to patient’s age and chondropathy. For operative treatment, proximal alignment surgery (lateral release, medial plication, medial patellofemoral ligament reconstruction), distal alignment surgery (tibial tubercle medialization), TT anteromedialization (Fulkerson operation), TT anteriorization, trochleoplasty or combined methods are used. Nowadays, MPFL reconstruction with hamstring or quadriceps tendon is the most commonly used method and it has successful results.
