What is the recommended management of an adult patellar fracture, including indications for non‑operative versus operative treatment, pain control, weight‑bearing, and rehabilitation based on fracture displacement and extensor mechanism integrity?

Management of Adult Patellar Fractures

For displaced patellar fractures (>2-3 mm articular step-off, >1-4 mm displacement, or disrupted extensor mechanism), surgical fixation is mandatory, while undisplaced fractures with intact extensor mechanism can be managed non-operatively. 1, 2

Initial Assessment

Evaluate extensor mechanism integrity first - this is the critical determinant of treatment strategy:

• Test active knee extension against gravity (straight leg raise) 3
• Assess for palpable defect in the retinaculum 4
• Measure fracture displacement and articular step-off on radiographs 1, 2
• Consider CT imaging pre-operatively, as it frequently changes both classification and treatment planning by revealing fracture complexity not apparent on plain films 1

Treatment Algorithm

Non-Operative Management Indications

Reserve for fractures meeting ALL of the following criteria:

• Displacement <2-3 mm 1, 2
• Articular step-off <2 mm 1, 2
• Intact extensor mechanism (able to perform straight leg raise) 1
• Closed fracture 2

Non-operative protocol:

• Immobilization in extension (knee immobilizer or cylinder cast) 1
• Multimodal analgesia for pain control 1
• Early range of motion exercises as pain permits to prevent knee stiffness 1
• Progressive weight-bearing as tolerated 1

Operative Management Indications

Surgery is required for fractures with ANY of the following:

• Articular step-off >2 mm 1, 2
• Fracture displacement >3 mm 2
• Disrupted extensor mechanism (inability to perform straight leg raise) 1, 2, 3
• Open fractures 2

Surgical Technique Selection

For simple transverse two-part fractures:

• Two parallel cannulated lag screws combined with anterior tension band wiring is the gold standard, providing superior biomechanical stability 5
• Modified tension band wiring alone can be used for most fracture patterns 5, 2

For comminuted fractures:

• Anatomical reconstruction of the articular surface is mandatory to prevent post-traumatic osteoarthritis 1
• Supplement tension band constructs with interfragmentary screws, cerclage wire/suture, or plate-and-screw constructs when comminution makes standard fixation inadequate 3
• Partial patellectomy may be necessary for severely comminuted fragments, but total patellectomy should only be considered as a salvage procedure due to significant quadriceps power loss and poor outcomes 5, 3

Critical Technical Considerations

Meticulous soft-tissue handling is paramount due to the patella's tenuous blood supply and limited soft-tissue envelope 2:

• Minimize periosteal stripping during exposure 2
• Repair retinacular tears meticulously to restore extensor mechanism continuity 4
• Use low-profile implants when possible to minimize soft-tissue irritation 2

Postoperative Management

Rehabilitation protocol:

• Early mobilization to prevent knee stiffness, which is a common disabling complication 1
• Progressive range of motion exercises 1
• Weight-bearing as tolerated based on fixation stability 1
• Plan for hardware removal after fracture healing, as implant-related pain requiring removal is extremely common 1

Common Pitfalls

Failure to achieve anatomical articular reduction leads to inevitable post-traumatic patellofemoral osteoarthritis 1, 3:

• Even minor articular incongruity causes long-term detrimental effects 2
• CT imaging pre-operatively prevents underestimating fracture complexity 1

Inadequate assessment of extensor mechanism integrity results in inappropriate non-operative treatment of displaced fractures requiring surgery 3

Delayed mobilization significantly increases risk of permanent knee stiffness and functional disability 1