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Imaging of the patellofemoral joint (PFJ) is
both customary and innovative: the narrowed
joint space, the very definition of osteoarthritis
pathology, is routinely detected using standard
radiological assessment. Early degenerative
chondral lesions are detected using slice
imaging: arthro-CT scans, commonly used in
France, MRI and its new acquisition sequences
or even MRI arthrography with an intra-
articular injection of Gadolinium.
Joint impairment involves the lateral
compartment of the PFJ in 90% of cases and
encompasses four etiologies:
- Primary patellofemoral joint osteoarthritis
(OA),
- Patellofemoral joint OA with instability: the
patient has a history of patellar dislocation,
- Traumatic patellofemoral joint OA: history of
patellar fracture,
- Articular chondrocalcinosis.
Imaging procedures are used to study this
etiological framework, which is particularly
crucial for determining the treatment.
Question 1:
Is there
degenerative impairment of
the patellofemoral joint?
Standard radiological assessments
Standard radiological assessments include
front views extended in monopodal stance,
schuss, lateral view extended in 30° of flexion,
axial view of the patella at 30° of flexion.
The Iwano classification describes the four
stages of joint space impairment on the axial
view of the patella (fig. 1).
- Stage 1:
mild OA joint space at least 3mm.
- Stage 2:
moderate OA; joint line narrowing
> 3mm.
- Stage 3:
severe OA; joint line narrowing
< 3mm
-
Stage 4:
very severe OA, joint surfaces
entirely touch each other.
Radiological assessments are aimed at detecting
certain etiological factors:
- Chondrocalcinosis is, in particular, charac
terized by a jagged, uneven aspect of the joint
surfaces. Meniscal calcifications are not
specific to articular chondrocalcinosis.
- Patellar fracture sequelae are generally
revealed during medical questioning; on the
X-ray, the patella appears enlarged trans
versally.
Patellofemoral chondral lesions:
MRI and arthro-CT scan
MRI and arthro-CT scans are indicated in the
case of diagnostic doubt about early arthrosis,
without joint space narrowing upon first
assessment or with radiological anomalies that
do not explain the pain [15, 16]. Given the
development of cartilage repair techniques,
there is increasing interest in detecting early
chondral lesions.
Imaging of Patellofemoral
Joint Osteoarthritis
C. Lapra, S. Chomel, M. Bakir