Approach
- As for knee examination
- Inspection
- Visible swelling
- skin involvement
- Palpation
- Pulsatile or expansile (aneurysm)
- Fluctuant (cystic swelling)
- Compressible (saphena varix)
- Transilluminable (cystic swelling)
Completion
- Continue with rest of knee examination
- Neurological and peripheral vascular examination including peripheral pulses
- Examine joint above (hip) and joint below (knee)
Differential diagnosis
- Skin / subcutaneous tissues
- lipoma
- sebacous cyst
- Vascular
- popliteal aneurysm
- saphena varix of saphenopopliteal junction
- Deep vein thrombosis
- Other
- Nerve - neuroma
- Enlarged bursae: associated with semimembranousus and medial head of gastronemus
- Baker's cyst: associated with degenerative changes in the knee joint, and popliteal cysts (enlargement of popliteal bursae)
Boundaries of popliteal fossa
- superiomedial: semimembranosus / semitendinosus
- superolateral: biceps
- inferiomedial: medial head of gastrocnemius
- inferolateral: lateral head of gastrocnemius
- Roof = fascia lata
- Floor = popliteal surface of femur, capsule of the knee joint and popliteus msucle covered by fascia
Bakers Cyst
- Posterior herniation of knee joint capsule
- Leads to escape of synovial fluid into one of the posterior bursae, stiffness and knee swelling
- Often associated with degenerative knee joint disease
- Diagnosis confirmed by USS examination - identification of fluid between semimembranosus and medial gastrocnemius tendons
- Aspiration possible, although recurrence common
- Important to rule out DVT
Popliteal cyst
- Usually located on the medial side of the popliteal fossa, just distal to the flexion crease of the knee under medial head of gastrocnemius
- Found in chiuldren and young adults
- Twice as common in boys compared with gfirls
- Usually unilateral
- Becomes more prominent when knee extended
- Firm, can be transilluminated
- Rx: aspirated or surgically excised