How should I manage a patellar fracture, including assessment, imaging, treatment options, pain control, antibiotics, VTE prophylaxis, immobilization, weight bearing, rehabilitation, and follow‑up?

Patellar Fracture Care Plan

Initial Assessment and Imaging

Obtain anteroposterior and lateral knee radiographs immediately to classify the fracture pattern and assess displacement. 1

• Look specifically for: displacement >2-3 mm, articular step-off >2-3 mm, comminution pattern, and integrity of the extensor mechanism (ability to perform straight leg raise against gravity) 1
• If radiographs show a fracture but clinical findings seem inconsistent, or if high suspicion exists despite negative radiographs, obtain CT without contrast to better characterize fracture complexity—CT changes both classification and treatment in a significant proportion of cases 1
• MRI is not routinely needed for acute patellar fractures unless soft tissue injury (quadriceps or patellar tendon rupture) is suspected 2

Treatment Decision Algorithm

Surgical fixation is indicated for: (1) displacement >2-3 mm, (2) articular step-off >2-3 mm, (3) disruption of the extensor mechanism (inability to perform straight leg raise), or (4) open fractures. 1

Conservative treatment is appropriate only for truly undisplaced fractures (<2 mm displacement, <2 mm step-off) with an intact extensor mechanism (documented ability to perform straight leg raise). 1

Surgical Management

For transverse fractures: Use modified tension band wiring technique, which provides the best functional outcomes. 3

For comminuted fractures: Consider high-strength braided non-absorbable suture techniques (suture mesh or "cobweb" technique) to avoid hardware-related complications while achieving rigid fixation. 4

• Anatomical reconstruction of the articular surface is mandatory to prevent posttraumatic osteoarthritis 1
• For severely comminuted fractures with no major fragments containing articular surface, patellectomy may be necessary 3
• Vertical fractures can be treated with mini cancellous screws or lag-screw fixation 3
• Inferior pole fractures should be treated with non-absorbable braided suture fixation woven through the patellar tendon and drill holes, which has lower reoperation rates (7.6%) compared to tension band wiring (30.6%) 5

Conservative Management Protocol

Immobilize in a knee immobilizer or cylinder cast in full extension for 4-6 weeks. 6

• Allow weight-bearing as tolerated with crutches or walker from the outset to prevent deconditioning 2
• Repeat radiographs at 2 weeks to confirm no displacement has occurred 1

Pain Management

Provide multimodal analgesia including acetaminophen, NSAIDs (if not contraindicated), and short-term opioids for severe pain. 2

• Adequate pain control is essential for early mobilization and preventing complications 2

Antibiotic Prophylaxis

Administer preoperative antibiotics (typically cefazolin 2g IV) within 60 minutes of surgical incision for operative cases. 2

• For open fractures, continue antibiotics until definitive wound closure 2

VTE Prophylaxis

Initiate pharmacologic VTE prophylaxis (low molecular weight heparin or direct oral anticoagulant) and continue for 4 weeks postoperatively for surgical cases. 7

• Mechanical prophylaxis (sequential compression devices) should be used perioperatively 7
• For conservative management, consider VTE prophylaxis in patients with additional risk factors (obesity, immobility, prior VTE) 2

Postoperative Immobilization and Weight-Bearing

Allow immediate weight-bearing as tolerated with assistive device (crutches or walker) after surgical fixation. 7

Begin gentle range-of-motion exercises at 3-5 days postoperatively once initial pain subsides, progressing from passive to active-assisted to active motion. 8

• Avoid complete immobilization—early mobilization prevents complications including pneumonia, DVT, and pressure ulcers 7
• For tension band fixation: Begin protected range of motion at 0-90 degrees for first 2 weeks, then progress as tolerated 3
• For suture fixation: Similar early mobilization protocol with gradual progression 5
• Full active extension should be achieved by 6 weeks 1

Rehabilitation Protocol

Progress to resistance exercises only after achieving pain-free range of motion, typically at 3-4 weeks. 8

• Quadriceps strengthening (isometric initially, then isotonic) is critical to restore extensor mechanism function 2
• Include long-term balance training to prevent falls and subsequent fractures 7
• Return to impact activities only after full pain-free function is restored, typically 6-8 weeks minimum 8
• Most patients achieve good to moderate results (90% combined) with appropriate surgical technique and rehabilitation 3

Follow-Up Schedule

Evaluate at 2 weeks (wound check and radiographs), 6 weeks (radiographs and ROM assessment), 12 weeks (functional assessment), and 6-12 months (final outcome assessment). 1

• At each visit, assess for: wound healing, hardware complications, loss of reduction, knee range of motion compared to contralateral side, and extensor lag 3, 5
• If pain or edema worsens or fails to improve by 2 weeks, obtain additional imaging to evaluate for complications 8

Common Pitfalls and Complications

Hardware removal is frequently required after tension band fixation due to implant-related pain (30.6% reoperation rate), whereas suture fixation has significantly lower reoperation rates (7.6%). 5

• Monitor for loss of reduction, which occurs more commonly with inadequate initial fixation 6
• Knee stiffness is the most common complication—aggressive early mobilization is essential to prevent this 1
• Posttraumatic osteoarthritis develops when articular surface is not anatomically restored 1
• Patients requiring reoperation or hardware removal have significantly diminished range of motion (p<0.005) 5

Secondary Fracture Prevention

Systematically evaluate all patients aged 50 years and over for osteoporosis risk and initiate appropriate treatment. 2

• Ensure adequate calcium and vitamin D intake 2
• Consider pharmacologic osteoporosis treatment for high-risk patients 2