The term cartilage injury or articular cartilage injury summarizes a spectrum of different cartilage lesions that are usually used in the context of hyaline cartilage damage within diarthrodial joints.
In a narrower sense, the term cartilage injury describes types of articular injury with sparing of bone and the subchondral bone plate. If the latter is affected this is referred to as osteochondral injury.
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Epidemiology
Cartilage injuries are quite common, especially among athletes, with a suggested overall prevalence as high as 36% in knees alone in that population. Cartilage injuries are often associated with ligamentous injuries 1,2.
Clinical presentation
Symptoms will vary depending on the type, extent and chronicity of the cartilage injury and include swelling, pain and decreased range of motion of the affected joint as well as stiffness or instability.
Complications
The typical complication of cartilage injury is early osteoarthritis of the affected joint.
Pathology
The pathologic correlate of cartilage injury is characterized by the cell death of chondrocytes resulting in different defect patterns or chondral discontinuities.
Etiology
Cartilage injuries result from trauma or repetitive loading due to overuse and are caused by different forms of stress and loading forces respectively as compression and shear forces by direct blunt trauma, indirect impact loading and/or torsional loading 3-5. Tension forces affecting diarthrodial joints mainly act on tendons and ligaments but can cause secondary cartilage injury.
Subtypes
Different types of cartilage injury include 3,4:
chondral fissure (compression)
chondral fracture (compression)
chondral delamination (shear forces)
chondral defect
Radiographic features
Cartilage injuries are best evaluated on MRI, MR or CT arthrography. Features vary with the type of injury.
MRI
Intermediate weighted images are most widely clinically used for musculoskeletal imaging and also in the evaluation of cartilage injury together with usual T1 weighted, T2 weighted and PD weighted images.
More recent techniques as T2 mapping, diffusion-weighted imaging, sodium MRI, dGEMRIC, T1 rho and ultra-short TE sequences are still more subject to research than clinical application 5.
Usual characteristics for different lesions include 5:
acute traumatic lesions: sharply demarcated margins with a narrow transition zone
degenerative lesions: shallow defects with a wide transition zone
Location of the cartilaginous defects is classified according to ICRS alphanumerical mapping system 8.
A common grading system for chondral defects is the modified Outerbridge classification.
CT/MR arthrography
Both techniques have high accuracy similar sensitivity and specificity especially for higher grade cartilage lesions 4.
Treatment and prognosis
Treatment depends on type, extent, the acuity of the lesion, symptoms as well as the age and activity of the patient and range from direct repair with bio-absorbable pins or screws, over mere debridement and lavage to the different cartilage repair and reconstruction methods 1,6,7.
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