Background

OCD MFC Loose BilateralLoose OCD MFC MRI

 

Definition

 

Focal idiopathic abnormality of subchondral bone

 

Bone begins to separate from its surrounding area due to disruption in blood supply

 

May result in instability and disruption of adjacent articular cartilage

 

Epidemiology

 

4 x more common in boys

- most common in the knee

- most commonly age 12 - 19 years (peak age 15)

 

16% bilateral knees affected

 

Brown et al. AJSM 2020

- 61 knees undergoing osteochondral allograft for OCD

- 2/3 of patients with either lateral or medial OCD had malalignment / mechanical axis deviation

 

Higher risk of knee OCD with childhood obesity

 

Groups

 

2 main groups

 

1.  Juvenile osteochondritis dissecans (JOCD)

- open phyes

 

2.  Adult osteochondritis dissecans (AOCD)

- closed physes

- many thought to be late presenting juvenile disease

- may be separate entity

 

Etiology Theories

 

Thought to be often multi-factorial / combination of theories

 

Repetitive microtrauma

 

Many children are heavily active in sport

- repetitive twisting

- repetitive impingement of tibial spine on the lateral aspect of MFC

 

Ischaemia

 

Studies demonstrate different vascular patterns at site of OCD

May predispose to interruption of blood supply with microtrauma

 

Genetic

 

Seen in identical twins

 

Pathology

 

4 stages

- initial osteopenia

- become edematous, likely due to trabecular microfracture

- develop a sclerotic ring between normal and abnormal bone

- develop fibrocartilaginous tissue at interval, and detach

 

Symptoms

 

Variable

- pain

- stiffness

- swelling

- locking

 

Xray

 

Intercondylar view / notch / tunnel view imperative

- most commonly seen in this view

- can miss the lesion unless have flexed knee view 30-50o

 

Knee OCD Xray Type 3Knee OCD Rosenberg View

 

Femoral OCDFemoral OCD 2

 

Xray classification

 

Stage 1:  Normal / abnormal MRI

Stage 2:  Lucent area of subchondral bone, can have surrounding sclerosis

Stage 3:  Partial loosening

Stage 4:  Completely detached / loose body

 

Type 2 OCDType 3 OCDType 4 OCD

Type 2                                             Type 3                                                  Type 3

 

MRI Classification

 

Stage 1:  Low signal changes, articular cartilage intact (stable)

Stage 2:  Articular cartilage breached, low signal indicating fibrocartilage behind fragment (stable)

Stage 3:  Articular cartilage breached, high signal indicating synovial fluid behind fragment (unstable)

Stage 4:  Loose body (unstable)

 

Look for

- integrity of the articular cartilage

- fluid behind the lesion, suggesting instability

- displacement of the lesion

 

Stable

- no synovial fluid behind lesion

 

Unstable

- cartilage breach with synovial fluid behind lesion

 

Stage 1.  Articular cartilage intact

 

Stage 1 OCD MRIStage 1 OCD MRI

 

Stage 2.  Articular cartilage breach, but low signal intensity behind fragment

 

Knee OCD MRI Partially DetachedFemoral OCD Type 3 MRI

 

Stage 3.  Articular cartilage breach and synovial fluid behind fragment (unstable)

 

Femoral OCD Type 3 MRIUnstable trochlea OCD with cartilage cleftTrochlea OCD cartilage cleft

 

Cartilage breach 1Cartilage breach 2

 

Stage 4.  Loose body

 

MRI Knee Displaced OCDKnee MRI type 4Knee OCD Type 3

Minimally displaced loose body

 

Knee OCD MRI Displaced and Empty Crater

Completely detached

 

ICRS Arthroscopic Classification

 

1. Cartilage Intact 

 

2. Partial discontinuity but stable on probing

 

Femoral OCD Type 2 Arthroscopic

 

3. Completely detached but insitu

 

Type 3 OCD Femur Arthroscopy

 

4.  Fully detached with crater & loose body

 

A. Chondral Fragment Salvageable

- recent

 

B. Chondral fragment unsalvageable

- increased in size / change in shape

 

Knee OCD Arthroscopy Fully DetachedKnee OCD Arthroscopy Type 4

 

Type 4 Knee OCD ArthroscopyFemoral OCD Type 4 Non salvageableKnee OCD Fragments

 

Displaced OCD 1Displaced OCD 2Displaced OCD 3

 

MRI and Arthroscopy correlation

 

Heywood et al. Arthroscopy 2011

- MRI predicted 21/23 OCD to be unstable

- arthroscopy found 10/23 OCD to be unstable

- false positives associated with high signal intensity at bone-fragment interface

 

Location

 

Medial Femoral Condyle 85%

- lateral aspect of the MFC

- PCL origin

 

Knee OCD Medial Femoral CondyleFemoral OCD

 

Lateral Femoral Condyle 10%

- most common in the central region of the LFC

 

Knee OCD Lateral Femur APKnee OCD Lateral OCD

 

Patellofemoral Joint 5%

- typically lateral trochlea

 

Trochlea OCD xrayTrochlea OCD Post Patella DislocationTrochlea OCD Post Patella DIslocation Sagittal

 

Patella OCD

 

Patella OCD