Patellar Tendon Rupture

Patellar tendon rupture is disruption of the tendon between the inferior pole of the patella and the tibial tuberosity. It typically affects men under 40, in contrast to quadriceps tendon rupture. It follows forceful eccentric quadriceps contraction in jumping or landing. Tears occur most often at the inferior patellar pole, less often in the midsubstance or at the tibial tubercle.

Risk factors: chronic patellar tendinopathy (jumper's knee), local corticosteroid injection, fluoroquinolone use, systemic inflammatory disease, chronic kidney disease, and prior bone-tendon-bone graft harvest. Tears are acute or chronic (over 6 weeks), and chronic cases are complicated by tendon retraction and patella alta.

• Sudden pain, a pop and inability to bear weight
• Hemarthrosis, an infrapatellar gap, a high riding patella
• Extensor lag or inability to straight leg raise
• Red flags: bilateral rupture (look for systemic disease), open wound, and concurrent cruciate injury

• Clinical examination for the gap and extensor failure.
• Lateral radiograph in 30 degrees of flexion: patella alta (Insall-Salvati ratio over 1.2 or Caton-Deschamps over 1.2), avulsed bone.
• Ultrasound or MRI to show the tear site, retraction and associated injuries.
• Metabolic and inflammatory screen when the cause is unclear.

Differentials: quadriceps tendon rupture, patellar fracture, tibial tubercle avulsion fracture, Osgood-Schlatter disease, severe patellar tendinopathy.

Complete tear: surgical repair as early as possible, ideally within 2 weeks.

• Acute: Krackow sutures through patellar tunnels or suture anchors, with augmentation by cerclage wire, tape or suture to protect the repair (set at 45 degrees flexion, matching the patella height to the other knee on radiograph).
• Chronic: reconstruction with hamstring or Achilles tendon allograft, sometimes preceded by traction or staged mobilization to restore patellar height.
• Cefazolin 2 g IV before incision (3 g if over 120 kg).
• Postoperative: hinged brace locked in extension for 2 weeks when walking, then 0 to 90 degrees flexion at 6 weeks, full motion by 12 weeks, jogging at 4 to 5 months and sports at 6 to 9 months.

Partial tear: immobilization in extension for 4 to 6 weeks, then rehabilitation.

Pain control: ibuprofen 400 mg orally every 8 hours with food for 5 to 7 days, with paracetamol 1 g every 6 hours.

Complications: re-rupture (up to 5%), quadriceps weakness, patella baja, stiffness, infection, anterior knee pain.

Review the cause (steroid, fluoroquinolone, systemic disease). Follow up at 2 and 6 weeks, 3 and 6 months. Counsel on a slow return to impact activity.