Meniscal Cysts

Epidemiology

 

Most common in lateral meniscus 9:1

 

Peak incidence 20-40

 

Aetiology

 

Probably 2° to infiltration of joint fluid into extra-articular tissues

- almost always associated with horizontal cleavage tear

- creates a flap valve in lateral 1/3 of LM

 

Symptoms

 

Usually present with pain

- activity related

 

May notice lump

- can vary in size with activity

 

Signs

 

Lateral mass associated with lateral joint line

- usually anterior to LCL

 

Best seen with knee in extension or slight flexion

- may disappear with knee flexion

 

Usually firm & immobile

- transilluminate

 

DDx

 

Ganglion

Cacific deposit in MCL / LCL

Osteochondroma

Soft tissue tumour

 

MRI

 

Meniscal tear + associated lateral meniscal cyst

 

MRI Lateral Meniscal CystMRI Lateral Meniscal Cyst 2MRI Anterior Lateral Meniscal Tear

 

Meniscal cyst 1Meniscal Cyst 2Meniscal cyst 3

 

Management 

 

Options

 

1.  Arthroscopic resection of tear

 

Tear may be difficult to identify

- careful inspection & probing

- often on undersurface of meniscus

- probe passed through tear into cyst

- usually results in decompression of cyst

- defunction flap valve with meniscectomy

 

Lateral Meniscus Cyst Normal Looking MeniscusLateral Meniscal Cyst Anterior Horn TearLateral Meniscal Cyst Defunction with Fluid

 

2.  Meniscal repair and cyst decompression

 

Results

 

Hulet et al Arthroscopy 2004

- incidence of 1.5% in 8000 knee arthroscopies

- 104 partial lateral meniscectomies

- intra-articular debridement in 91 and open cystectomy in 14

- 11 cysts recurred

- good or excellent results in 87%