MRI of patellar disorders

MRI of Patellar Disorders

Dr. Bhavin JankhariaJankharia Imaging

Patellar Disoders

PF Joint•How to diagnose acute subluxation / dislocation

and not to miss the diagnosis especially when the patella has reduced back

Patellar Disoders



•How to evaluate PF incongruence

Patellar Disoders



•How to evaluate PF incongruence•Chondromalacia

Acute Injury

PF Joint

Acute•Dislocation / subluxation•Retinaculum and medial patellofemoral ligament

tears•Chondral lesions

Marrow Edema Anterior Lateral Femoral Condyle

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

Here the edema is straightforward….

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

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

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

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

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).

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

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.

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)

PF Joint

Acute Subluxation / Dislocation•Marrow edema of the anterior LFC is a clue

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

Patellofemoral Incongruence

There are various parameters that we can use to assess PF

incongruence. They are listed in the next few slides

PF Joint

• Measurements–Patellar length

Chhabra et al. Skeletal Radiol (2011) 40:375 387

patellar tendon length / patellar bone long axis length greater than 1.3 usually

suggests patella alta

PF Joint

• Measurements–Patellar length–Translation


greater than 2 mm difference between the medial edges is considered significant

PF Joint

• Measurements–Patellar length–Translation–Abnormal tilt


Lateral patellar angle less than 8 degrees is significant. The angle

should open laterally.

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

PF Joint



Lateral femoral condylar protrusion greater than 8 mm suggests overgrowth

PF Joint



–Tibial tubercle - trochlear groove distance


Distance greater than 15mm suggests an abnormal TT-TG distance

PF Joint



–Tibial tubercle - trochlear groove distance


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


Old PF Injury

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

patellar subluxation

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

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

Chondromalacia

Chondromalacia Patellae

• Cartilage softening, swelling, fibrillation in young patients

• Staging– Gd 1: softening,

swelling

Elias DA. Clin Radiol 2004; : 543



• Staging– Gd 1: softening,

swelling– Gd 2: fragmentation,

fissuring upto 1.3mm




• Staging– Gd 1: softening, swelling– Gd 2: fragmentation,

fissuring upto 1.3mm– Gd 3: fissuring > 1.3mm





fissuring upto 1.3mm– Gd 3: fissuring > 1.3mm





fissuring upto 1.3mm– Gd 3: fissuring > 1.3mm– Gd 4: cartilage loss down

to subchondral bone





fissuring upto 1.3mm– Gd 3: fissuring > 1.3mm– Gd 4: cartilage loss down

to subchondral bone


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

Dynamic Imaging and Patellar Tracking

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

Dynamic Imaging

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

Patellar Disoders



•How to evaluate PF incongruence•Chondromalacia

Thank You

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MRI of patellar disorders