Differentials
Deep vein thrombosis (DVT)
SIGNS / SYMPTOMS
Patients may have underlying risk factors for development of DVT.
May present with acute calf pain and/or swelling without associated knee pathology.
INVESTIGATIONS
Venous ultrasound will demonstrate thrombus inside the vein.
Popliteal haematoma
SIGNS / SYMPTOMS
Patients may have a history of recent trauma or treatment with anticoagulants.
INVESTIGATIONS
Ultrasound will demonstrate a haematoma in the affected area.
CT and MRI can also identify the haematoma.
Popliteal muscle tear
SIGNS / SYMPTOMS
May cause pain out of proportion localised at the site of the tear.
INVESTIGATIONS
Ultrasound, MRI, and CT will demonstrate the muscle tear.
Knee effusion
SIGNS / SYMPTOMS
May lead to excessive intra-articular fluid in areas other than the cyst location.
INVESTIGATIONS
Ultrasound, MRI, and CT will demonstrate the knee effusion.
Popliteal artery aneurysm
SIGNS / SYMPTOMS
May cause a pulsatile mass in the popliteal fossa.
INVESTIGATIONS
Arterial ultrasound will demonstrate the aneurysm.
Popliteal vein aneurysm
SIGNS / SYMPTOMS
May cause a soft compressible mass in the popliteal fossa.
INVESTIGATIONS
Venous ultrasound will demonstrate popliteal vein aneurysm.
Popliteal soft tissue mass
SIGNS / SYMPTOMS
May cause a palpable firm mass in the popliteal fossa.
INVESTIGATIONS
Ultrasound, MRI, and CT will demonstrate the mass. Sarcoma will have a heterogeneous appearance.
Popliteal lymphocele
SIGNS / SYMPTOMS
Typically a firmer palpable mass than popliteal cyst.
INVESTIGATIONS
Duplex ultrasound demonstrates cyst with clear fluid and acoustic enhancement posteriorly.
Popliteal abscess
SIGNS / SYMPTOMS
May cause a tender, fluctuant collection with erythema in the popliteal fossa.
There may be signs of infection such as fever.
INVESTIGATIONS
Duplex ultrasound or CT scan will demonstrate non-cystic, heterogeneous collection.
Popliteal fossa varicosities
SIGNS / SYMPTOMS
There may be visible varicosities in the popliteal fossa.
INVESTIGATIONS
Venous duplex will demonstrate varicosities.
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