1736

Accumulation of joint fluid in the area behind the knee.

The most common mass of the popliteal fossa.

In elderly frequently associated with knee arthritis.

Can be caused by the herniation of the knee joint capsule into the back of the knee, commonly associated with tear in the meniscal cartilage.

A synovial cyst resulting from fluid distention of the gastrocnemius-semitendinosus bursa.

Affects both genders.

Affects all races.

Typically affects adults.

Rarely affects children with rheumatoid arthritis or trauma.

Associated processes include: osteoarthritis, rheumatoid arthritis, gout, systemic lupus, infections, long-standing dialysis and derangements of anterior cruciate ligament, tears in meniscus and osteochondral fractures.

Lies between the tendons of the medial head of the semimembranous and gastrocnemius muscles, and posterior to the femoral condyle.

In general not associated with symptoms.

May cause stiffness or other discomfort.

Indicated by the presence of a soft tissue mass at the back of the knee.

May rupture and be associated with pain, swelling and bruising.

Patients typically present with a popliteal swelling, aching, effusion and they may experience buckling, locking of the knee or cracking.

May be associated with a limited range of motion.

Complications: rupture or dissection with a pseudo-thrombophlebitis syndrome, DVT, pulmonary embolism, leakage, infection, and posterior compartment syndrome.

0.2%-11% patients have coexisting DVT.

Translumination can demonstrate the fluid nature of the mass.

Diagnosis confirmed by ultrasound, CT, arthroscopy, or MRI.

Often no treatment is needed.

Treatment involves assisted weight-bearing, anti-inflammatory agents, and ice therapy.

The cyst can be drained or rarely removed surgically if the cyst is problematic.

Long term disability rare.

Usually disappears over time