Quadriceps Tendon Rupture

Quadriceps tendon rupture is disruption of the extensor tendon at or near its patellar insertion. Incidence is about 1.4 per 100,000 a year, mostly in men over 40 (male to female about 8 to 1), with a peak at 50 to 60 years. The usual mechanism is eccentric quadriceps contraction against a flexed knee during a fall or misstep.

Risk factors: diabetes, chronic kidney disease, gout, rheumatoid arthritis, hyperparathyroidism, obesity, corticosteroid use, fluoroquinolone and statin use, and prior tendinopathy. Ruptures are partial or complete. A complete rupture disrupts extension unless the retinacula are intact. Delay beyond 2 to 3 weeks worsens outcomes through retraction and scarring.

• Sudden pain, a palpable suprapatellar gap, hemarthrosis and swelling
• Inability to perform a straight leg raise, or extensor lag
• Patella baja in complete tears
• Some patients can extend the knee if the retinacula are intact, which can lead to a missed diagnosis
• Red flags: bilateral or spontaneous rupture (look for metabolic or systemic disease), and open wounds

• Clinical examination for the gap and extensor mechanism failure.
• Lateral radiograph: patella baja (Insall-Salvati ratio under 0.8), suprapatellar soft tissue swelling, avulsed bone fragments.
• Ultrasound (rapid, dynamic) and MRI to define partial versus complete tears and the retraction.
• Metabolic screen when spontaneous: glucose, HbA1c, creatinine, calcium, parathyroid hormone, urate.

Differentials: patellar fracture, patellar tendon rupture, quadriceps contusion, femoral nerve palsy, prepatellar bursitis.

Partial tear with intact active extension: knee immobilizer in full extension for 4 to 6 weeks with weight bearing as tolerated, then progressive range of motion and strengthening.

Complete tear: surgical repair as early as possible (within 2 weeks).

• Krackow type locking sutures through three transosseous patellar tunnels, or suture anchors. Augment with a tension band or tape in poor tissue.
• Cefazolin 2 g IV before incision (3 g if over 120 kg).
• Postoperative: locked brace in extension for 6 weeks with weight bearing as tolerated. Motion 0 to 45 degrees at week 2, 0 to 90 degrees by week 6, full by 12 weeks. Return to sport at 6 months.
• Chronic ruptures: reconstruction with Achilles or hamstring allograft or autograft, or a Scuderi turndown flap.
• Complications: re-rupture (about 2%), loss of extension strength, stiffness, infection, heterotopic ossification, venous thromboembolism (consider enoxaparin 40 mg SC daily for 14 days in high risk patients).

Address contributing disease and review any fluoroquinolone or steroid exposure. Follow up at 2 and 6 weeks, 3 and 6 months. Counsel on rehabilitation adherence.