Fractures of the Patella
The patella (kneecap) is the largest sesamoid bone in the body. It increases the mechanical advantage of the quadriceps mechanism. Fractures here disrupt the extensor apparatus.
1. Mechanism & Types
- Direct Injury: Fall on the knee. Causes Comminuted/Stellate fractures (often retinaculum is intact).
- Indirect Injury: Violent quadriceps contraction. Causes Transverse fractures with retinacular tears (Gap appears).
2. Management
- Undisplaced (< 2-3mm step): Cylindrical Cast (Tube cast) for 4-6 weeks.
- Displaced Transverse: Tension Band Wiring (TBW). Converts tensile force of quads into compressive force at the fracture site.
- Comminuted: Cerclage wiring or Patellectomy (Partial or Total) if reconstruction is impossible.
3. Physiotherapy
Key Concept: Extensor Lag
Loss of active extension despite full passive extension. Indicates quadriceps weakness or lengthening of the extensor mechanism (after patellectomy). Focus on Straight Leg Raises (SLR) and VMO strengthening.
Loss of active extension despite full passive extension. Indicates quadriceps weakness or lengthening of the extensor mechanism (after patellectomy). Focus on Straight Leg Raises (SLR) and VMO strengthening.
25 Practice MCQs
Q1. The patella is a:
Answer: A). Embedded within the quadriceps tendon.
Q2. Tension Band Wiring (TBW) is used for:
Answer: A). Requires a clean fracture line to compress.
Q3. Indirect injury (Quad contraction) typically causes:
Answer: A). The muscle pulls the top half up.
Q4. Direct trauma (fall on knee) typically causes:
Answer: B). The bone is crushed against the femur. Retinaculum usually intact.
Q5. Function of the patella:
Answer: A). Extends the knee with less force.
Q6. Total Patellectomy results in:
Answer: A). The fulcrum is lost.
Q7. Bipartite Patella is:
Answer: A). Often mistaken for fracture. Smooth edges on X-ray.
Q8. Conservative treatment involves:
Answer: A). Knee must be straight to relax the quads.
Q9. TBW allows for:
Answer: A). Dynamic compression principle.
Q10. Indications for surgery:
Answer: A). Disrupted extensor mechanism needs repair.
Q11. Partial Patellectomy usually preserves the:
Answer: A). To maintain the quad insertion leverage.
Q12. Active knee extension test checks for:
Answer: A). If patient cannot lift leg straight, surgery is needed.
Q13. Skyline View (Sunrise view) is best for:
Answer: A). Shows the articular surface congruence.
Q14. Chondromalacia Patella is:
Answer: A). Common long-term sequelae or independent condition.
Q15. Q-Angle is formed by lines between:
Answer: A). Normal 10-15 deg. Increased angle = dislocation risk.
Q16. Hardware removal is common because:
Answer: A). Patella is very superficial.
Q17. Vertical fractures are usually:
Answer: A). Muscle pull doesn't separate fragments.
Q18. Patella Alta means:
Answer: A). Insall-Salvati ratio > 1.2.
Q19. Patella Baja means:
Answer: A). Often seen after trauma/surgery.
Q20. Sleeve fracture occurs in:
Answer: A). Often missed on X-ray.
Q21. Quadriceps setting exercises (Isometrics) should start:
Answer: A). Safe inside the cast.
Q22. Dislocation of patella is usually:
Answer: A). Due to Q-angle pull.
Q23. Apprehension Test is for:
Answer: A). Patient fears lateral push.
Q24. Screw fixation alone (without wire) is good for:
Answer: B). Compression screws work well here.
Q25. Knee flexion during rehab is usually limited to:
Answer: A). Progresses as healing confirms.
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