Wk 4, Case 2 - Review

Patient History
20-year-old male with right knee pain and swelling 1 week after dislocation.

Findings
Menisci:

Medial Meniscus: Tiny undersurface flap tear posterior horn-body junction.

Lateral Meniscus: Intact. Meniscal flounce adjacent to the inner edge of the meniscal body.

Ligaments:

Anterior Cruciate Ligament: Intact.

Posterior Cruciate Ligament: Intact.

Medial Collateral Ligament: Thickened tibial collateral ligament with increased intrasubstance signal involving the proximal and mid portions with diffuse periligamentous edema, consistent with an low to intermediate grade sprain. Partial-thickness tear of the anterior tibial collateral ligament fibers adjacent to the femoral origin of the medial patellofemoral ligament. Diffusely swollen lax meniscofemoral and meniscotibial ligaments consistent with sprains.

Lateral Collateral Ligament: Intact.

Posterolateral Corner Structures: Intact.

Posteromedial Corner Structures: Intact.

Extensor Mechanism:

Patellar Tendon: Intact.

Distal Quadriceps Tendon: Intact.

Medial Patellofemoral Ligament: Massive tear with rupture of the medial patellofemoral ligament. Avulsion of the distal patella attachment with associated small cortical avulsion fracture. Avulsed proximal femoral attachment with a large gap between the femoral attachment footplate/adductor tubercle and the avulsed medial patellofemoral ligament fragment (at least 5.1 cm gap).

Medial and Lateral Patellar Retinacula: Diffusely torn medial markedly lax patellar retinaculum. Thickened lateral patellar retinaculum.

Hoffa’s Fat Pad: Diffusely contused Hoffa’s fat pad with increased signal.

Articulations:

Patellofemoral Compartment: Moderate to marked laterally subluxed patella. Small cortical avulsion fracture of the medial patella, in the region of the usual medial patellofemoral ligament attachment. Trochlear dysplasia with medial facet hypoplasia and insufficient trochlear groove (Dejour type C). Wiberg 2 patella. Increased TT-TG distance measuring 2.0 cm. Patella alta with Insall-Salvati ratio 2.0 cm. No traumatic chondral or osteochondral lesion.

Medial Compartment: Unremarkable.

Lateral Compartment: Unremarkable.

General:

Bones: Lateral femoral condyle kissing contusion with diffuse marrow edema.

Effusion: Massive hemarthrosis with heterogeneous intermediate to low signal organizing hematoma.

Baker’s Cyst: Moderate amount of fluid tracking along myofascial planes deep to the medial head of the gastrocnemius and superficial to the popliteus muscle belly, which could represent recent dehisced/ruptured Baker’s cyst or myofascial injury.

Loose Bodies: None.

Other, soft tissue and Neurovascular: Diffusely increased signal with fiber discontinuity involving the distal sartorius tendon and myotendinous junction, consistent with intermediate grade strain and partial-thickness tear.

Conclusion
Recent transient patellar dislocation-relocation event with the following:

1.Patellar remains moderately laterally subluxed.
2.Massive rupture medial patellofemoral ligament and medial retinaculum.
3.Avulsion fracture medial patella at the MPFL footplate with corresponding bony kissing contusion of the lateral femoral condyle.
4.Concomitant large hemarthrosis with organizing hematoma.
5.Background of high grade trochlear dysplasia (Dejour C), patella alta and increased TT-TG distance of 2.0cm.
6.Intermediate grade strain with partial distal sartorius tendon tear.
7.Low to intermediate grade (grade I-II) MCL sprain (involving layer II tibial collateral ligament, and layer I meniscofemoral and coronary/meniscotibial ligaments).