Cartilage Grading

Chondromalacia can be divided into 4 grades by MRI, using fat saturated proton density sequences. This grading system is the modified Outerbridge grading system

    •    grade I

         ◦ focal areas of hyperintensity with normal contour 

         ◦ arthroscopically : softening or swelling of cartilage

    •    grade II

         ◦ blister-like swelling/ fraying of articular cartilage extending to surface

         ◦ arthroscopically : fragmentation and fissuring within soft areas of articular cartilage

    •    grade III

         ◦ partial thickness cartilage loss with focal ulceration

         ◦ arthroscopically : partial thickness cartilage loss with fibrillation (crab-meat appearance)

    •    grade IV

         ◦ full thickness cartilage loss with underlying bone reactive changes

         ◦ arthroscopically : cartilage destruction with exposed subchondral bone

Osteochondral injury staging system for MRI attempts to grade the stability and severity of osteochondral injury and is used to plan management. 

    •    stage I

         ◦ injury limited to articular cartilage

         ◦ subchondral oedema

         ◦ X-ray findings : none

    •    stage II

         ◦ cartilage injury with associated subchondral fracture

         ◦ thin sclerotic margin

         ◦ X-ray findings : usually none; may see fracture as sclerotic or osteopaenic area

    •    stage III

         ◦ high signal around osteochondral fracture (rim sign) but not displaced

         ◦ separation begins at the margins of the fragment

         ◦ X-ray findings : slight lucency between osteochondral fragment and remainder of the bone

    •    stage IV

         ◦ osteochondral fragment displaced

         ◦ usually joint effusion present, surrounding fragment and filling donor site

         ◦ X-ray findings: increased lucency between osteochondral fragment and remainder of the bone, or loose body with donor site

         ◦ irregularity

    •    stage V

         ◦ subchondral cyst formation

         ◦ secondary degenerative change

         ◦ X-ray findings : secondary osteoarthrits

Osteochondritis dissecans can be classified at surgery into 4 stages:

    •    stage I

         ◦ stable

         ◦ subchondral bone flattening and abnormal increased T2 signal with intact cartilage

         ◦ arthoscopy:  softening without breach

    •    stage IIA

         ◦ stable

         ◦ subchondral cyst formation with minimal edema

         ◦ arthroscopy:  breached cartilage that is stable

    •    stage IIB

         ◦ unstable

         ◦ incomplete separation of osteochondral fragment with edema at interface with adjacent bone, increased cystic change

    •    stage III

         ◦ unstable

         ◦ cleft of fluid undermining an undetached, undisplaced osteochondral fragment

         ◦ arthroscopy:  definable fragment that remains partially attached (flap lesion)

    •    stage IV

         ◦ unstable.  dislocated fragment

         ◦ complete detachment and separation of fragment, which can be loose and free within the joint.

         ◦ arthroscopy:  loose body and osteochondral defect at the the donor site.