Articular Cartilage

10.1055/b-0034-92256

Articular Cartilage

Grading of Cartilage Lesions

The radiologic grading of articular cartilage lesions by magnetic resonance imaging (MRI), MR arthrography, or computed tomographic (CT) arthrography in the clinical setting is based on surgical and arthroscopic classification systems. Cartilage lesions can be classified according to their morphologic appearance, depth, size, and location. Various authors have proposed clinical classification systems that take into account one or more of these features.

Outerbridge Classification

The classic Outerbridge classification defines four grades of chondromalacia ( Table 13.1 ).

The Outerbridge classification implies a staged progression of cartilage damage and is therefore limited to the description of degenerative cartilage lesions. Because Outerbridge developed this classification for the progression of chondromalacia patellae, its original version can be strictly applied only to the patellar cartilage. Ultimately, however, all arthroscopic classifications are based on this grading system to some degree.

Outerbridge RE. The etiology of chondromalacia patellae. J Bone Joint Surg Br 1961;43-B:752–757

Outerbridge classification of articular cartilage lesions
Grade	Description
1	Softening and swelling (closed chondromalacia)
2	Fragmentation and fissuring < ½ inch (< 1.3 cm) in diameter
3	Fragmentation and fissuring > ½ inch (> 1.3 cm) in diameter
4	Erosion of cartilage down to bone

Shahriaree Classification

The grading system proposed by Shahriaree builds directly on the Outerbridge classification. It comprises four grades of chondromalacia, and distinguishes between a more localized basal degeneration and superficial degeneration that usually involves extensive surfaces of the articular cartilage ( Table 13.2 ). In the original article, the author assumed that this categorization might facilitate differentiation between traumatic and degenerative lesions. However, over the years, this classification, like the Outerbridge system, turned out to be applicable only to degenerative cartilage lesions.

Shahriaree H. Chondromalacia. Contemp Orthop 1985;11: 27–39

Shahriaree system for the arthroscopic classification of cartilage lesions
Grade	Basal degeneration	Superficial degeneration
1	Softening	Fibrillation
2	Blister formation	Fissure formation
3	Ulceration and “crabmeat” formation	Fragmentation
4	Crater formation and eburnation	Crater formation and eburnation

Noyes and Stabler Classification

The Noyes and Stabler classification ( Table 13.3 ) was developed for the knee joint and basically defines only three different lesion grades. Grade 1 indicates softened cartilage with an intact surface. Grades 2 and 3 describe superficial defects of varying depth, irrespective of defect morphology. The size and location of the cartilage lesions are also classified. Additionally, the examiner states the degree of knee flexion where the lesion is in weight-bearing contact (e.g., 20–45° of flexion).

Noyes FR, Stabler CL. A system for grading articular cartilage lesions at arthroscopy. Am J Sports Med 1989;17(4):505–513

Noyes and Stabler system for the arthroscopic classification of cartilage lesions
Grade	Extent of involvement	Surface description	Diameter (all grades)	Location (all grades)
1A	Definite softening with some resilience remaining	Cartilage surface intact	< 10 mm ≤ 15 mm ≤ 20 mm ≤ 25 mm > 25 mm	Patella: Proximal, middle, distal third Medial facet, ridge, lateral facet Trochlea: Medial femoral condyle: Anterior third Middle third Posterior third Lateral femoral condyle: Anterior third Middle third Posterior third Medial tibial condyle: Anterior third Middle third Posterior third Lateral tibial condyle: Anterior third Middle third Posterior third
1B	Extensive softening with loss of resilience (deformation)	Cartilage surface intact
2A	< Half thickness	Cartilage surface damaged; cracks, fissures, fibrillation, or fragmentation
2B	≥ Half thickness
3A	Bone surface intact	Bone exposed
3B	Bone surface cavitation	Bone exposed