knee)

🦴 Anatomy - Bones, Ligaments & More

• Bones: Femur, Tibia, Patella. Fibula is non-articulating.
  • Key surfaces: Femoral condyles, Tibial plateaus.
• Cruciate Ligaments (Intra-articular):
  • ACL: Prevents anterior tibial translation.
  • PCL: Prevents posterior tibial translation.
• Collateral Ligaments (Extra-articular):
  • MCL: Resists valgus stress (force from lateral side).
  • LCL: Resists varus stress (force from medial side).
• Menisci: Fibrocartilage shock absorbers.
  • Medial: C-shaped, attached to MCL.
  • Lateral: O-shaped, more mobile.
• Popliteal Fossa: Contains Popliteal artery/vein, Tibial & Common peroneal nerves.

⭐ The "Unhappy Triad" (O'Donoghue's): A common injury pattern from a lateral blow to a planted foot, classically involving the ACL, MCL, and Medial Meniscus.

🩺 Clinical Manifestations - Reading the Signs

• Pain Location:
  • Anterior: Patellofemoral pain, patellar tendinopathy.
  • Medial/Lateral: Collateral ligament (MCL/LCL) or meniscal tears, osteoarthritis.
  • Posterior: Baker's cyst, PCL injury.
• Swelling (Effusion):
  • Rapid (hours): Hemarthrosis → ACL tear, intra-articular fracture.
  • Slow (24-48h): Synovial fluid → Meniscal tear, inflammatory arthritis.
• Mechanical Symptoms:
  • Locking/Catching: Suggests meniscal tear or a loose body.
  • Giving Way/Instability: Classic for ligamentous injury (esp. ACL).
  • Crepitus: Grinding sound; indicates chondromalacia or osteoarthritis.

⭐ The "unhappy triad" (O'Donoghue's) is a classic pattern: simultaneous injury to the ACL, MCL, and medial meniscus from a valgus stress.

🕵️ Diagnosis - The Detective Work

• Imaging & Procedures:
  • X-ray: First-line for trauma/fracture (use Ottawa Knee Rules) & osteoarthritis (joint space narrowing, osteophytes).
  • MRI: Gold standard for soft tissue: ligaments (ACL, PCL), menisci, cartilage.
  • CT Scan: Best for complex fractures and surgical planning.
  • Arthrocentesis: Crucial for suspected septic arthritis (WBC > 50,000) or crystal arthropathy (gout/pseudogout).

⭐ The "unhappy triad" (ACL tear, MCL tear, medial meniscus tear) is a classic association, but an isolated ACL tear or ACL with a lateral meniscus tear is more common.

🛠️ Management - The Repair Shop

• Conservative First: RICE (Rest, Ice, Compression, Elevation), NSAIDs, physical therapy (PT), and activity modification are initial steps for most non-acute/stable injuries.

• Surgical Interventions:

  • ACL Repair: Arthroscopic reconstruction is standard.
    • Autograft: Patellar tendon (gold standard), hamstring tendon.
    • Allograft: Cadaveric tendon; often for older, less active patients.
  • Meniscal Tears:
    • Repair: Sutured if in the outer, vascular "red zone."
    • Meniscectomy: Resected if in the inner, avascular "white zone."
  • Collateral Ligaments (MCL/LCL): Often managed non-operatively with bracing. Surgery for Grade III tears or multi-ligament injuries.
  • Total Knee Arthroplasty (TKA): For end-stage osteoarthritis refractory to conservative management.

⭐ Unhappy Triad (O'Donoghue's Triad): A classic severe knee injury from a valgus force, involving tears of the ACL, MCL, and medial meniscus.

⚡ Biggest Takeaways

• ACL tears are common non-contact pivot injuries; test with the Lachman test (most sensitive) and anterior drawer sign.
• PCL tears typically result from "dashboard injuries"; assess with the posterior drawer test.
• The "unhappy triad" involves injury to the ACL, MCL, and medial meniscus, often from a lateral blow.
• Meniscal tears present with joint line tenderness, locking, and a positive McMurray test.
• MCL/LCL tears are diagnosed with valgus/varus stress tests, respectively.
• Patellar dislocation is almost always lateral.