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Baker's Cyst (Popliteal Cyst) After Knee Surgery: Evaluation and Management

Postoperative Popliteal Cyst: A Structured Approach

A fluid-filled swelling behind the knee after surgery is often a Baker's cyst—synovial fluid herniating through the posterior capsule. While concerning, it is manageable with a stepwise algorithm.

Step 1: Surgical Follow-Up

Contact your operating surgeon. They know the intraoperative findings (meniscal repair, chondral work, capsule closure) which dictate cyst significance.

Step 2: Clinical Assessment

  • Size, fluctuance, tenderness, range of motion (ROM) limitation.
  • Rule out DVT (calf tenderness, swelling, Homan's sign) – requires urgent ultrasound if suspected.
  • Assess wound healing, signs of infection.

Step 3: Imaging

  • Ultrasound: First-line. Confirms cystic nature, size, communication with joint, rules out mass/DVT.
  • MRI: If internal derangement (meniscus, loose body) suspected as driver.

Step 4: Conservative Management (First-Line)

  • RICE: Rest, Ice (15–20 min q4–6h), Compression (neoprene sleeve, not tourniquet), Elevation.
  • Activity Modification: Avoid deep flexion, prolonged standing, impact.
  • NSAIDs: Ibuprofen/naproxen for inflammation (if no contraindications).
  • PT Guidance: Quad sets, SLR, gentle ROM per protocol. Avoid hamstring stretching if cyst tense.

Step 5: Interventional Options

  • Aspiration + Corticosteroid Injection: Under ultrasound guidance. Diagnostic (fluid analysis) and therapeutic. Recurrence ~30–50%.
  • Address Intra-articular Pathology: If cyst driven by meniscal tear, loose body, synovitis—arthroscopic treatment of primary cause resolves cyst in >80%.

Step 6: Surgical Excision (Rare)

Reserved for large, symptomatic, recurrent cysts with no intra-articular pathology. Posterior approach; risk to neurovascular bundle.

Red Flags – Seek Immediate Care

  • Calf swelling/pain (DVT/ruptured cyst mimic)
  • Fever, wound drainage, spreading erythema
  • Sudden size increase, numbness/weakness in foot

Most postoperative cysts resolve with time and conservative care. Partner with your surgeon—don't self-manage.

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