[Retracted] Discovering Knee Osteoarthritis Imaging Features for Diagnosis and Prognosis: Review of Manual Imaging Grading and Machine Learning Approaches

Table 3

Summary of knee OA grading systems based on imaging modalities.

Imaging modalities	OA grading system	Examined OA features	Pros	Cons
X-ray images	KL	(i) Osteophyte	(i) Universally accepted knee OA grading system	(i) Overemphasizes the significance of osteophytes as compared to JSN
		(ii) JSN	(ii) Indicates OA changes in medial compartment better	(ii) Poor reliability for OA changes in lateral compartment
		(iii) Bone end deformity		(iii) Poor inter- and intraobserver reliabilities
		(iv) Subchondral sclerosis
	Ahlbäck	(i) JSN	(i) Greater emphasis on JSN than osteophytes by assuming the joint space reduction as an indirect sign of cartilage loss	(i) Poor inter- and intraobserver reliabilities
		(ii) Bone attrition
	Brandt	(i) Percentage of JSN	(i) Greater emphasis on JSN than osteophytes	(i) Poor inter- and intraobserver reliabilities
		(ii) JSN associated osteophytes	(ii) Good correlation with arthroscopic damage
		(iii) JSN associated subchondral sclerosis
		(iv) JSN associated subchondral cysts
	OARSI	(i) Percentage of JSN	(i) Most widely used individual OA feature scale with example images	(i) Only focus on JSN feature
	IKDC	(i) Joint space width	(ii) Best combination of good interobserver reliability and medium correlation with arthroscopic findings	(i) Only focus on joint space width
	Fair bank	(i) Squaring of tibial margin	(i) Involves many radiographic features	(i) Limited to post-meniscectomy condition
		(ii) Flattening of femoral condyle		(ii) Lack of knowledge about its reliability
		(iii) Sclerosis of tibial margin
		(iv) Hypertrophic changes
		(v) JSN
	Jäger-Wirth	(i) Osteophytes	(i) Involves many radiographic features.	(i) Lack of knowledge about its reliability
		(ii) JSN
		(iii) Arthrosis
MRI images	Modified Outerbridge classification	(i) Fat-saturated proton density sequences of chondromalacia patella and chondral surface	(i) Greater emphasis on cartilage morphology	(i) Require validation with arthroscopic examination
				(ii) No bony assessment
	WORMS	(i) Cartilage	(i) Greater emphasis on cartilage and bone morphologies	(i) Tedious interpretation task
		(ii) Bone marrow lesions
		(iii) Subchondral cysts
		(iv) Bone attrition
		(v) Osteophytes
		(vi) Effusion synovitis
		(vii) Meniscal tears
		(viii) Ligaments
		(ix) Periarticular cysts
		(x) Bursitis
		(xi) Loose bodies
	KOSS	(i) Cartilage	(i) Greater emphasis on cartilage and bone morphologies	(i) Tedious interpretation task
		(ii) Bone marrow lesions
		(iii) Subchondral cysts
		(iv) Osteophytes
		(v) Effusion synovitis
		(vi) Synovial thickening
		(vii) Meniscal extrusion
		(viii) Meniscal tears
		(ix) Popliteal cysts
	BLOKS	(i) Cartilage	(i) Greater emphasis on cartilage and bone morphologies	(i) Tedious interpretation task
		(ii) Bone marrow lesions
		(iii) Osteophytes
		(iv) Effusion synovitis
		(v) Hoffa synovitis
		(vi) Meniscal extrusion
		(vii) Intrameniscal signal
		(viii) Meniscal tears
		(ix) Meniscal maceration
		(x) Meniscal cyst
		(xi) Ligaments
		(xii) Periarticular cysts
		(xiii) Bursitis
		(xiv) Loose bodies
	MOAKS	(i) Cartilage	(i) Greater emphasis on cartilage and bone morphologies	(i) Tedious interpretation task
		(ii) Bone marrow lesions	(ii) Cover most OA features
		(iii) Osteophytes
		(iv) Effusion synovitis
		(v) Hoffa synovitis
		(vi) Meniscal extrusion
		(vii) Intrameniscal signal
		(viii) Meniscal tears
		(ix) Meniscal maceration
		(x) Meniscal cyst
		(xi) Hypertrophy
		(xii) Ligaments
		(xiii)Periarticular cysts
		(xiv) Bursitis
		(xv) Loose bodies
CT images	OACT	(i) JSN	(i) Emphasis on two knee compartments: tibiofemoral and patellofemoral joints	(i) Lack of validation result
		(ii) Osteophytes
		(iii) Cysts
		(iv) Sclerosis
Ultrasonography	Ultrasonographic grading scale	(i) Osteophytes	(i) Depends on the shape of distal femoral osteophytes	(i) Features may be distorted by noise
		(ii) Projection from femoral condyle		(ii) Limited to primary knee OA
OCT images	DJD classification	(i) Cartilage surface irregularities	(i) Deep examination of cartilage	(i) Difficult to collect samples
		(ii) Tissue disorganization in cartilage		(ii) Only focuses on cartilage changes
		(iii) Fibrocartilaginous regeneration
		(iv) Cartilage erosion