Osteochondrosis of Superior Pole of Patella

Clinically young male patient with athletic background complaining of typical unilateral anterior knee pain. Marked tenderness at the superior pole of patella.

This MRI study of knee joint shows abnormal irregularity, fragmentation with sclerosis involving superior pole of patella. An associated thickening of quadriceps tendon. 

Knee joint effusion.

Imaging findings consistent with osteochondrosis of patella at superior pole.

Osteochondrosis of the superior pole of the patella

Osteochondroses are the heterogeneous group of injuries to the epiphyses and apophyses of children or adolescents, are actually osteonecrosis owing to repetitive microtrauma and avulsion injuries at tendinous insertions. Imaging wise characterized by bone fragmentation and sclerosis.

There are two well-known such syndromes associated with knee joint, one is Osgood-Schlatter disease, an avulsion of the tibial tuberosity and another is Sinding-Larsen-Johansson disease, a chronic avulsion injury involving lower pole of the patella at the insertion of patellar tendon.

The less well described osteochondrosis at the superior pole of patella appears secondary to similar mechanism associated with quadriceps tendon insertion, a rare cause of anterior knee pain in children between 5 and 10 years of age, usually single knee is affected but bilateral cases have also been reported.

Excessive lateral pressure syndrome MRI

This MRI Axial STIR sections of knee show clinical marker on skin on anteromedial aspect of knee joint. There is patellar tilt, articulating surface of patella facing medially, abnormal thickening of lateral patellar retinaculum and patellofemoral ligament. Associated bone marrow oedema involving lateral margin of lateral articulating facet of patella.

Imaging findings consistent with clinical diagnosis of Excessive lateral pressure syndrome.

Lateral Patellar Compression Syndrome

Synonym : Excessive lateral pressure syndrome, ELPS

This is another common cause of anterior knee pain.

The improper tracking of the patella in the trochlear groove generally caused by imbalance between medial and lateral dynamic stabilizers of knee, the tight lateral retinaculum restricting the patellar mobility with excessive lateral tilt of patella causing friction between lateral articulating facet of patella with lateral trochlea of femur.

Typically affects adults, patient presents with pain on compression of the patella, lateral facet tenderness. Condition is aggravated physical activity.

This is mainly a clinical diagnosis. However, lateral tilt of patella on axial sections of MRI or sunrise knee radiographs, patella facing medially without lateral translation should be depicted meticulously which is very commonly overlooked during MRI interpretation. Furthermore, abnormal thickening and shortening of lateral patellar retinaculum and lateral patellofemoral ligament could be appreciated on MRI. Nonetheless, the important ancillary findings on MRI are subchondral bone marrow oedema, cystic geodes involving lateral articulating facet of patella and adjacent lateral femoral trochlea facing the patella. The patellofemoral angle is calculated on axial sections, the medial opening of the angle, that is demonstration of angle more than 8° can support the diagnosis of ELPS.

Treatment is mainly conservative with physiotherapy focusing on quadriceps stretching and strengthening. Operative lateral retinaculum release is reserved for refractory cases. 

Medial patellar plica syndrome

Clinically young patient presented with anteromedial knee pain.

MRI sagittal T2 and axial T2 images delineates a linear well-defined low signal intensity band running across medial patellofemoral recess. However, there is no obvious associated bone marrow oedema involving medial articulating facet of patella or medial femoral trochlea. Mild associated joint effusion.

Medial plica mentioned in the report with joint effusion.

Medial plica syndrome

Synonym: synovial plicae of the knee.

The another common cause of anterior knee pain typically present with pain on anteromedial aspect of the knee, just cranial to the joint line with or without associated with crepitation, catching and locking sensations. Typically involves young with athletic background. 

There are actually synovial invaginations as a part of remnants of embryological development. They are encountered in MRI over 70% of individuals and are mostly asymptomatic. However these tags can get inflamed secondary to repetitive friction and stretching, making patient symptomatic. They can undergo fibrosis after long standing inflammation imparting them non-stretchable restricting the joint movement and painful.

In symptomatic patients, medial plica seen as low signal intensity band on T1 as well as T2-weighted images with an associated chondral defect involving medial articulating facet of patella.

Treatment is mainly conservative, physiotherapy and intra articular steroid injections.