A short presentation on the practical issues related to the patellofemoral joint (subluxation, dislocation and incongruence) and chondromalacia

1. MRI of Patellar Disorders
Dr. Bhavin Jankharia
Jankharia Imaging

2. Patellar Disoders
PF Joint
• How to diagnose acute subluxation / dislocation
and not to miss the diagnosis especially when
the patella has reduced back

3. Patellar Disoders
PF Joint
• How to diagnose acute subluxation / dislocation
and not to miss the diagnosis especially when
the patella has reduced back
• How to evaluate PF incongruence

4. Patellar Disoders
PF Joint
• How to diagnose acute subluxation / dislocation
and not to miss the diagnosis especially when
the patella has reduced back
• How to evaluate PF incongruence
• Chondromalacia

5. Acute Injury

6. PF Joint
Acute
• Dislocation / subluxation
• Retinaculum and medial patellofemoral ligament
tears
• Chondral lesions

7. Marrow Edema Anterior Lateral Femoral
Condyle

8. When marrow edema is seen in the anterior
aspect of the lateral femoral condyle, our
antennae need to go up for the presence of
an acute lateral patellar subluxation /
dislocation

9. Here the edema is straightforward….

10. ….as are the associated lateral patellar tilt and subluxation (red arrow) and
acute chondral defect (yellow arrow)

11. It is when the patella has reduced and the only positive finding is the
marrow contusion (arrow)

12. that it becomes necessary to look at the patella and the medial
patellofemoral ligament (MPFL), which is edematous, contused and torn
with subtle lateral patellar translation, best seen on the T2W axial MRI

13. A review of the anterior most STIR coronal images often will show
marrow contusion of the medial patellar facet subjacent to the
attachment of the MPFL

14. The MPFL avulsion tear at the patellar attachment is along the inferior aspect
(yellow arrow) with involvement of the whole MPFL up to the anterior femoral
attachment of the medial collateral ligament (MCL) (blue arrow). Note the
marrow contusion in the anterior LFC (red arrow).

15. Sometimes, the MPFL injury may be a bony avulsion (red arrow)

16. The MPFL tear can also be at the femoral attachment (red arrow), in which
case, often the anterior aspect of the femoral attachment of the MCL (blue
arrow) may be involved.

17. Chondral defects (red arrow) may occur due to the shear stress of the
subluxation / dislocation and an effort should be made to look for additional
cartilage fragments (blue arrow)

18. PF Joint
Acute Subluxation / Dislocation
• Marrow edema of the anterior LFC is a clue

19. PF Joint
Acute Subluxation / Dislocation
• Marrow edema of the anterior LFC is a clue
• If seen, look at the patellar marrow, cartilage,
MPFL and congruence

20. Patellofemoral Incongruence

21. There are various parameters that
we can use to assess PF
incongruence. They are listed in
the next few slides

22. PF Joint
• Measurements
– Patellar length
patellar tendon length / patellar bone long
axis length greater than 1.3 usually
suggests patella alta
Chhabra et al. Skeletal Radiol (2011) 40:375
387

23. PF Joint
• Measurements
– Patellar length
– Translation
greater than 2 mm difference between the
medial edges is considered significant
Chhabra et al. Skeletal Radiol (2011) 40:375
387

24. PF Joint
• Measurements
– Patellar length
– Translation
– Abnormal tilt
Lateral patellar angle less than 8
degrees is significant. The angle
should open laterally.
Chhabra et al. Skeletal Radiol (2011) 40:375
387

25. PF Joint
• Measurements
– Patellar length
– Translation
– Abnormal tilt
– Trochlear sulcus depth
and lateral femoral
condylar overgrowth
Trochlear depth of 3mm or less and
trochlear angle greater than 145 degrees
suggests trochear dysplasia / hypoplasia
Chhabra et al. Skeletal Radiol (2011) 40:375
387

26. PF Joint
• Measurements
– Patellar length
– Translation
– Abnormal tilt
– Trochlear sulcus depth
and lateral femoral
condylar overgrowth
Lateral femoral condylar protrusion greater
than 8 mm suggests overgrowth

27. PF Joint
• Measurements
– Patellar length
– Translation
– Abnormal tilt
– Trochlear sulcus depth
and lateral femoral
condylar overgrowth
– Tibial tubercle - trochlear
groove distance
Distance greater than 15mm suggests an
abnormal TT-TG distance Chhabra et al. Skeletal Radiol (2011) 40:375
387

28. PF Joint
• Measurements
– Patellar length
– Translation
– Abnormal tilt
– Trochlear sulcus depth
and lateral femoral
condylar overgrowth
– Tibial tubercle - trochlear
groove distance
Chhabra et al. Skeletal Radiol (2011) 40:375
387

29. PF Joint
• Measurements
– Patellar length
– Translation
– Abnormal tilt
– Trochlear sulcus depth and lateral femoral condylar
overgrowth
– Tibial tubercle - trochlear groove distance
– Superolateral Hoffa's fat pad signal, etc
Chhabra et al. Skeletal Radiol (2011) 40:375
387

30. Old PF Injury

31. In some patients with PF
incongruence, a careful search
often reveals evidence of old,
perhaps undiagnosed lateral
patellar subluxation

32. This patient has PF incongruence with lateral patellar subluxation and
abnormal tilt with a loose body (red arrow)

33. A careful review of the patient in the previous slide shows an old avulsion
injury of the patellar attachment of the MPFL (red arrows)

34. Chondromalacia

35. Chondromalacia Patellae
• Cartilage softening,
swelling, fibrillation in
young patients
• Staging
– Gd 1: softening,
swelling
Elias DA. Clin Radiol 2004; : 543

36. Chondromalacia Patellae
• Cartilage softening,
swelling, fibrillation in
young patients
• Staging
– Gd 1: softening,
swelling
– Gd 2: fragmentation,
fissuring upto 1.3mm
Elias DA. Clin Radiol 2004; : 543

37. Chondromalacia Patellae
• Cartilage softening,
swelling, fibrillation in
young patients
• Staging
– Gd 1: softening, swelling
– Gd 2: fragmentation,
fissuring upto 1.3mm
– Gd 3: fissuring > 1.3mm
Elias DA. Clin Radiol 2004; : 543

38. Chondromalacia Patellae
• Cartilage softening,
swelling, fibrillation in
young patients
• Staging
– Gd 1: softening, swelling
– Gd 2: fragmentation,
fissuring upto 1.3mm
– Gd 3: fissuring > 1.3mm
Elias DA. Clin Radiol 2004; : 543

39. Chondromalacia Patellae
• Cartilage softening,
swelling, fibrillation in
young patients
• Staging
– Gd 1: softening, swelling
– Gd 2: fragmentation,
fissuring upto 1.3mm
– Gd 3: fissuring > 1.3mm
– Gd 4: cartilage loss down
to subchondral bone
Elias DA. Clin Radiol 2004; : 543

40. Chondromalacia Patellae
• Cartilage softening,
swelling, fibrillation in
young patients
• Staging
– Gd 1: softening, swelling
– Gd 2: fragmentation,
fissuring upto 1.3mm
– Gd 3: fissuring > 1.3mm
– Gd 4: cartilage loss down
to subchondral bone
Elias DA. Clin Radiol 2004; : 543

41. While there is some correlation
between PF incongruence and
acute lateral patellar subluxation,
repetitive subluxation and
chondromalacia, each of these
can exist without the other

42. Dynamic Imaging and Patellar Tracking

43. As a rule patellar tracking can be done
clinically. The mere demonstration of a
tracking abnormality on either static or
dynamic real-time images is usually not
clinically relevant

44. Dynamic Imaging
• Patello-femoral joint
– Tracking
– Patellar subluxation and tilt
– Passive, active, with our without loading

45. Patellar Disoders
PF Joint
• How to diagnose acute subluxation / dislocation
and not to miss the diagnosis especially when
the patella has reduced back
• How to evaluate PF incongruence
• Chondromalacia

46. Thank You