1b (Knee) - Answer: 52-year-old female presents with left knee pain, swelling, and popping

HISTORY:

This 52-year-old female presents with left knee pain, swelling, and popping.

(QUIZ ANSWER) NOT A FINDING IN THIS CASE:

Traumatic tear of the anterior cruciate ligament (ACL).

Using the diagnostic web viewer, we have provided images that assist in telling our clinical story. Areas of significance are indicated below.

FINDINGS:

Skeletal: No acute fracture, stress fracture or osseous contusion.

Multi-centric chondral surface erosions weight-bearing medial compartment, lateral trochlea, patellofemoral compartment.

No traumatic tear or injury of the ACL, PCL, MCL or lateral collateral complex. No posterolateral or posteromedial corner injury.

Menisci: Chronic posterior horn-root tear lateral meniscus. Additional free edge radial tear 1-2 cm length. Inner third cleavage tear meniscal body. Juxtameniscal somewhat complex cyst may or may not have intrameniscal communication, 7.5 mm craniocaudad diameter. Chronic undersurface tear peripheral posterior horn-body junction medial meniscus.

Patellofemoral: Delamination medial and lateral facet, lateral tilt. Penetrating osseous edema lateral trochlea class 4 chondromalacia. MPFL is intact. Enthesophytic spurring superior pole patella. Quadriceps tendon, patellar tendon and flexor mechanism are unremarkable. Nominal preinsertional tendinosis semimembranosus.

Joint effusion with synovial hypertrophy. Additional multiple low signal foci are identified within the joint space. Whether this represents tiny metaplastic bodies or whether this is sequelae of prior surgery is not entirely certain. Infrapatellar scarring.

Complex mixed hemorrhagic and proteinaceous Baker's cyst craniocaudal diameter 4.9 cm, short-axis diameter 2.6 cm medially with additional myotendinous component associated with the medial gastrocnemius and resultant proximal muscle atrophy.

Penetrating chondromalacia lateral trochlea class 3, class 4 chondromalacia weightbearing central medial condyle and class 3 with focal class 4 chondromalacia in addition to eburnation subchondral lateral tibial plateau.

Curvilinear dark signal is seen within the articular cartilage. Chondrocalcinosis favors CPPD crystal deposition disease. Note preserved signal intensity within the popliteus tendon origin. Myotendinous edema is seen in the retrotibial popliteus.

Swollen Baker's cyst as dehisced with fluid dissecting alongside the medial and to lesser degree lateral gastrocnemius in the lower popliteal region.

Note swelling at the posterior horn capsulofascicle attachment associated with parasagittal and root lateral meniscus.

CONCLUSION:

1. Findings favor inflammatory arthropathy with complex hemorrhagic and proteinaceous Baker's cyst as well as infiltrative pseudocyst contributing to origin muscle atrophy of the medial gastrocnemius. Multiple small metaplastic intra-articular bodies, synovitis as well as chonedrocalcinosis noted. Consider CPPD or gout.

2. Multifocal class 4 / class 3 chondromalacia greatest in the lateral trochlea (patellofemoral) and medial central weight-bearing compartments.

3. Meniscal pathology: 1 cm undersurface tear peripheral posterior horn-body junction medial meniscus with longer radial tear posterior horn root, posterior horn and central body lateral meniscus at least 3 cm length.

4. Reactive fissuring of the medial patellar articular cartilage.

Discussion
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  MSK MRI
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