Cartilage

 

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

  1. grade I

    1. focal areas of hyperintensity with normal contour 

    2. arthroscopically : softening or swelling of cartilage

  2. grade II

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

    2. arthroscopically : fragmentation and fissuring within soft areas of articular cartilage

  3. grade III

    1. partial thickness cartilage loss with focal ulceration

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

  4. grade IV

    1. full thickness cartilage loss with underlying bone reactive changes

    2. 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. 

  1. stage I

    1. injury limited to articular cartilage

    2. subchondral oedema

    3. X-ray findings : none

  2. stage II

    1. cartilage injury with associated subchondral fracture

    2. thin sclerotic margin

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

  3. stage III

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

    2. separation begins at the margins of the fragment

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

  4. stage IV

    1. osteochondral fragment displaced

    2. usually joint effusion present, surrounding fragment and filling donor site

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

  5. stage V

    1. subchondral cyst formation

    2. secondary degenerative change

    3. X-ray findings : secondary osteoarthrits


Osteochondritis dissecans can be classified at surgery into 4 stages:

  1. stage I

    1. stable

    2. subchondral bone flattening and abnormal increased T2 signal with intact cartilage

    3. arthoscopy:  softening without breach

  2. stage IIA

    1. stable

    2. subchondral cyst formation with minimal edema

    3. arthroscopy:  breached cartilage that is stable

  3. stage IIB

    1. unstable

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

  4. stage III

    1. unstable

    2. cleft of fluid undermining an undetached, undisplaced osteochondral fragment

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

  5. stage IV

    1. unstable.  dislocated fragment

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

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