MRI Osteoarthritis Knee Score (MOAKS) is a semi-quantitative scoring tool published in 2011 that was developed from the Whole Organ Magnetic Resonance Imaging Score (WORMS) and Boston Leeds Osteoarthritis Knee Score (BLOKS) scoring tools 1-3.
Usage
MOAKS has been shown to have very good to excellent reliability in the resarch setting 1-3. MOAKS is the most widely accepted semi-quantitative scoring system for knee osteoarthritis 4.
Classification
Scoring is performed on MRI examinations without (intravenous or intra-articular) contrast 3.
Subregions
Fourteen subregions are defined for scoring articular cartilage and bone marrow lesions 1:
-
patella (axial view)
medial patella (including median patellar ridge)
lateral patella
-
femur
medial and lateral trochlea
medial and lateral central femur
medial and lateral posterior femur
-
tibia
anterior, central and posterior medial articular cartilage
anterior, central and posterior lateral articular cartilage
subspinous region (tibial spines)
N.B. lesions crossing two subregions are scored in both subregions.
Individual features
Bone marrow lesions and cysts
bone marrow lesion: ill-defined trabecular bone signal that is low on T1 and high on T2FS weighted imaging
cyst: well-defined regions of fluid signal adjacent to the subchondral bone plate
multiple bone marrow lesions in one subregion are collated into one percentage
-
scoring
-
subregional volume of bone marrow lesion (including cysts)
grade 0: none
grade 1: <33%
grade 2: 33-66%
grade 3: >66%
-
lesion per centage that is bone marrow lesion vs cyst
grade 0: none
grade 1: <33%
grade 2: 33-66%
grade 3: >66%
-
Articular cartilage
Articular cartilage is graded for lesion size (any cartilage loss) and degree of full-thickness loss:
-
size of cartilage loss as a percentage of subregion size
grade 0: none
grade 1: <10%
grade 2: 10-75%
grade 3: >75%
-
percentage of full-thickness cartilage loss in subregion
grade 0: none
grade 1: <10%
grade 2: 10-75%
grade 3: >75%
Osteophytes
Osteophytes are graded in 12 regions as none (grade 0), small (grade 1), medium (grade 2) or large (grade 3):
anterior femur (trochlea): medial and lateral (sagittal/axial)
posterior femur: medial and lateral (sagittal/axial)
central femur: medial and lateral (coronal)
patella: superior, inferior (sagittal) and medial, lateral (axial)
tibia: medial and lateral (coronal)
Hoffa's synovitis and synovitis-effusion
Mild chronic synovitis in MOAKS is described as diffuse high signal on T2/PD FS sequences within Hoffa's fat pad. It is scored on the sagittal view as:
grade 0: normal
grade 1: mild
grade 2: moderate
grade 3: severe
Effusion-synovitis is scored on the axial view as:
grade 0: physiological volume
grade 1: small; fluid continuous in the retropatellar space
grade 2: medium; slight convexity of the suprapatellar bursa
grade 3: large; evidence of capsular distension
Meniscus
Meniscal position and morphology are graded. Meniscal extrusion is graded as <2 mm (grade 0), 2-2.9 mm (grade 1), 3-4.9 mm (grade 2), and >5 mm (grade 3) and scored in four locations:
-
medial extrusion relative to medial tibial margin (coronal)
maximal anterior extrusion (sagittal)
-
lateral extrusion relative to lateral tibial margin (coronal)
maximal anterior extrusion (sagittal)
Morphology is scored at the anterior and posterior horns (sagittal) and body (coronal) for both medial and lateral menisci. The following features are scored as present (yes) or absent (no):
signal not extending through to meniscal surface on at least two slices
vertical tear (radial and longitudinal): must extend to both femoral and tibial surfaces
horizontal and radial tear: must extend from the periphery to either femoral or tibial surface
complex tear: ≥3 point involvement of the tibial and femoral surfaces
partial maceration
progressive partial maceration
complete maceration
meniscal hypertrophy
Ligaments/tendons
The following are scored:
-
normal vs complete tear
associated bone marrow lesion/cyst at site of insertion or origin
-
normal vs complete tear
associated bone marrow lesion/cyst at site of insertion or origin
-
normal signal vs signal abnormality
Periarticular features
The following structures are defined as being absent or present:
iliotibial band signal
infrapatellar bursa signal
prepatellar bursa signal
-
associated with the tibio-fibular joint
associated with the cruciate ligaments
other