Popliteal (Baker's) Cysts
Popliteal (Baker's) Cysts
Key Points
- Fluid-filled synovial cyst in the popliteal fossa
- More common in children aged 4-7 years
- Usually benign and self-limiting in children
- Often associated with underlying joint pathology
- Different etiology and management compared to adult Baker's cysts
Overview
Popliteal cysts, also known as Baker's cysts, are synovial fluid-filled lesions located in the popliteal fossa. In children, they often present as an incidental finding and may be asymptomatic. Unlike adults, pediatric popliteal cysts frequently occur without associated intra-articular pathology.
Pathophysiology
Anatomical Considerations:
- Formation mechanism:
- Distention of gastrocnemius-semimembranosus bursa
- Communication with knee joint space
- One-way valve mechanism
- Associated Conditions:
- Juvenile Idiopathic Arthritis (JIA)
- Trauma
- Synovitis
- Meniscal tears (rare in children)
Histopathology:
- Synovial lined cavity
- Fibrous wall composition
- Connection to knee joint via semimembranosus bursa
Clinical Presentation
History:
- Often asymptomatic
- Presenting complaints:
- Posterior knee swelling
- Mild discomfort with activity
- Feeling of tightness
- Occasional pain
- Associated symptoms:
- Joint stiffness
- Limited range of motion
- Activity-related discomfort
Physical Examination:
- Inspection:
- Visible posterior knee swelling
- Usually soft and non-tender
- More prominent with knee extension
- Palpation:
- Soft, compressible mass
- Usually non-tender
- Mobile in transverse plane
- Special Tests:
- Foucher's sign
- Transillumination test
Diagnosis & Assessment
Imaging Studies:
- Ultrasound:
- First-line imaging modality
- Shows anechoic or hypoechoic mass
- Can assess for complications
- MRI:
- Gold standard for evaluation
- Shows relationship to surrounding structures
- Identifies associated pathology
- T2-weighted images show fluid signal
- X-rays:
- Limited utility
- May show soft tissue shadow
- Rules out bony abnormalities
Differential Diagnosis:
- Soft tissue tumors
- Arterial aneurysms
- Deep vein thrombosis
- Ganglia
- Synovial sarcoma
Management
Conservative Treatment:
- Observation:
- First-line treatment in children
- Regular monitoring
- Spontaneous resolution common
- Activity Modification:
- Avoid aggravating activities
- Range of motion exercises
- Physical therapy if needed
Medical Management:
- NSAIDs for symptomatic relief
- Treatment of underlying condition if present
- Aspiration:
- Rarely indicated in children
- High recurrence rate
Surgical Management:
- Indications:
- Large, symptomatic cysts
- Failed conservative treatment
- Complications
- Surgical Options:
- Open excision
- Arthroscopic treatment
- Treatment of underlying pathology
Complications & Prognosis
Potential Complications:
- Rupture:
- Pseudo-thrombophlebitis
- Compartment syndrome (rare)
- Compression:
- Neurovascular compromise
- Deep vein thrombosis (rare)
- Recurrence after treatment
Prognosis:
- Generally excellent in children
- High rate of spontaneous resolution
- Better outcomes compared to adults
- Regular monitoring recommended
