Knee effusion

A knee effusion is a fluid accumulation in the intra-articular space of the knee

May be serous, bloody, or purulent
Etiology
- Osteoarthritis
- Trauma
- Crystal arthritis (gout)
- Rheumatoid arthritis
- Septic arthritis (infection)
- Ligament injuries
- Meniscus injuries
Clinical features
- Swelling around and above patella
- Decreased ROM
- Patellar ballottement
Diagnosis
- Swift diagnosis of septic arthritis is important to reduce complication
- X-ray
  - Check for OA or fracture
- Joint aspiration
  - Detect bacteria, crystals, blood
- MRI
  - Check for ligament injuries
Treatment
- RICE
- NSAIDs
- Depends on underlying cause
- Septic arthritis -> IV antibiotics

Popliteal cyst

Popliteal cyst, also called a Baker cyst, is a cyst in the popliteal fossa, between the semimembranosus and gastrocnemius
- The cyst consists of a gel-like material
- The cyst communicates with the synovium of the knee, so it’s not a true cyst
Etiology
- It forms on the basis of a chronic inflammation of the knee
- Osteoarthritis
- Meniscus injury
- Rheumatoid arthritis
Clinical features
- Often asymptomatic
- Pain
- Locking and clicking during movement
Diagnosis
- MRI
  - To look for meniscal problem
- X-ray
  - Osteoarthritis
Treatment
- Treat underlying conditions
- Surgical removal if there are complaints