MAGNETIC RESONANCE IMAGING OF CYSTIC KNEE LESIONS

 M. GONGI, W. HARZALLAH, M. OMRI, R. SALEM, MA. JELLALI, A. ZRIG, W. MNARI, M. MAATOUK, M. GOLLI

THE 5th PAN ARAB CONGRESS OF RADIOLOGY

 MUSCULOSKELETAL : MK 12

INTRODUCTION (1) :

- Cystic lesions around the knee are a diverse group of entities, frequently encountered during routine MRI of the knee.

- These lesions may produce overlapping clinical features, rendering the clinical diagnosis difficult.

INTRODUCTION (2) :

- MRI is the technique of choice in characterizing lesions around the knee: to confirm the cystic nature of the lesion, to evaluate the anatomical relationship to the joint and surrounding tissues, and to identify associated intra-articular disorders.

PURPOSE :

The purpose of this study is to review the MRI aspects of some cystic knee lesions.

MATERIALS AND METHODS :

- We retrospectively report 11 cases of cystic knee lesions collected in the radiology department of Fattouma Bourguiba Hospital of Monastir over a period of 5 years.

- All patients were explored by MRI (1.5 Tesla) for knee pain.

RESULTS :

- The most common lesion was Baker cyst, also termed popliteal cyst (5 cases).

- Meniscal cysts were found in 3 cases .

- A cyst of the ilio-tibial band was found in one case.

- Mucoid degeneration of the anterior cruciate ligament was diagnosed in 2 cases.

DISCUSSION :

1 - Popliteal (Baker’s) Cysts :

Popliteal cysts are lined with synovium and result from extrusion of joint fluid into the gastrocnemio-semimembranosus bursa through a weak portion of the postermedial capsule of the knee between the medial head of the gastrocnemius muscle and the semimembrannosus muscle.

- Size :The cyst can vary in size from quite small to very large.

- Age :It’s rare in chidren.

- Presentation :-asymptomatic +++ -painful popliteal swelling ,-knee effusion,-clicking of the knee,-buckling of the knee ..

- Complications :

- break :  table of pseudo-thrombophlebitis,- vascular or nerve compression, - synovial diseases : osteochondromatosis ..

On MR images, popliteal cysts usually appear as well-defined fluid collections. The presence of hemorrhage or debris within thecyst is not rare.

: popliteal cyst SM : semimembrannosus muscle G : gastrocnemius muscle

SM

G

SM

G

Hemorrhagic popliteal cyst

Large popliteal cyst

A popliteal cyst found in a child

2 - Meniscal Cysts

- Meniscal cysts characteristically are locatedat the joint line on the medial or lateral side of the knee and invariably are associated with an underlying horizontal meniscal tear.They are formed by extrusion of joint fluid, into the adjacent tissues, through this meniscal tear which leads directly into the cyst.

-Presentation :They are manifested by knee pain, locking and a mass adjacent to the joint line.

-On MR images, lateral meniscal cysts appear as well-defined rounded cysts located adjacent to a meniscal tear.Medial meniscal cysts tend to be larger and dissect away from the site of the tear . The meniscal tear is usually horizontal and extensive.

Lateral meniscal cyst

Meniscal cyst

Meniscal cyst

3 - Mucoïd degeneration of the anterior cruciate

ligament :

- The lesion presents with knee pain and restriction of flexion.

- The pathogenesis is unclear.

- It’s suspected in a patient with a physically intact ligament and no obvious trauma history.

- The lesion may manifest as an elongated cystalong the long axis of the ACL, or as an enlargedACL.

- Discrete intraosseous ganglia are observed in77% of the cases with mucoid degeneration of theACL. These ganglia consist of myxoid material andhave generally no identifiable communication withthe articular surface or joint cavity.-

The MR-findings of mucoid degeneration of the ACL include:- an ill-defined ACL,- an increased ligamentous girth,- a normal orientation of the ligament, - and an increased signal intensity on all sequences interspersed among visible intact ACL fibers.

Mucoid degeneration of the ACL

ACL

Mucoid degeneration of the ACL

a b

4 - Cyst of the ilio-tibial band :

Iliotibial band friction syndrome (ITBFS) is a common cause of lateral knee pain that is often related to intense physical activity, as occurs in long-distance runners, cyclists...

Clinical examination :tenderness over the lateral femoral epicondyle and reproducible pain during flexion and extension of the knee.

On MRI findings, there is a cyst located adjacent to Iliotibial band.

: cyst ITB : ilio-tibial band

ITB ITB

a b

c

CONCLUSION (1) :

- A wide variety of cystic lesions may be encountered in the soft tissues and bones during routine MR imaging of the knee.

- The ability of MR to visualize internal derangements of the knee and abnormalities of the surrounding soft tissues makes this technique ideally suited to the evaluation of these cystic lesions.

CONCLUSION (2) :

- MR diagnosis is also needed to avoid unnecessary arthroscopy and to guide specific therapy.