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Quadriceps Tendon Rupture

  • Rupture of the quadriceps tendon (knee extensor mechanism) results in an inability to extend the leg.
    • In patients >40 years old, rupture may be secondary to tendon degeneration.
  • Classification:
    • Complete versus incomplete
General Prevention
Stretching before athletics and thigh-strengthening exercises in patients with chronic tendinitis could provide some protection.
  • A rare occurrence
  • Can occur in any age group
  • Affects males more than females
Risk Factors
  • Trauma, usually in the setting of an underlying chronic tendinitis
  • Medical conditions such as renal disease, diabetes mellitus, gout, rheumatoid arthritis, chronic steroid use, obesity, lupus, hyperparathyroidism, and dialysis
  • Previous total knee arthroplasty
No known inheritance of predisposition to quadriceps tendon rupture
  • Tendon rupture can occur:
    • During attempts to regain balance to avoid a fall; maximum force can be placed across the quadriceps tendon when eccentric loading is placed on a semiflexed of knee.
    • Secondary to direct or penetrating knee trauma
Associated Conditions
Meniscal or knee ligament damage
Signs and Symptoms
  • Inability to extend the knee actively
  • Acute pain
  • Suprapatellar gap
  • Weak leg extension with partial rupture
  • Acute trauma
  • Attempt to regain balance before a fall, with a history of a chronic condition or tendinitis
Physical Exam
  • Inability to perform a straight-leg raise
  • Inability to actively extend the leg
  • Holding the knee in full extension may be possible if the knee retinaculum is intact; patients should be asked to extend the knee from the flexed position.
  • Palpation of a gap 1-2 cm proximal to the superior pole of the patellar; examination of the contralateral knee is important.
  • Nearly full passive ROM is possible.
  • Routine knee ligament examination is performed to ensure that no other damage has occurred.
  • Routine AP and lateral radiographs:
    • The patella is displaced distally on lateral radiographs.
    • May see calcifications in the presence of chronic tendinitis
  • MRI or ultrasound may be useful when the physical examination is inconclusive.
Pathological Findings
Degenerative changes are seen in the quadriceps tendon in patients with collagen vascular disease and in persons >40 years.
Differential Diagnosis
  • Patellar fracture
  • Patellar tendon rupture
  • Knee ligament injury
  • Quadriceps muscle rupture
General Measures
  • Partial tears with an intact extensor mechanism are rare.
    • Treated nonoperatively
    • The knee is immobilized in full extension with a brace or cast.
    • Protected ROM and strength training is begun after 6 weeks.
    • Weightbearing as tolerated with the knee braced
  • Complete tears:
    • Repaired surgically
    • Ideally, operative repair should be performed as soon as possible.
    • Quadriceps ruptures also may require quadriceps lengthening and augmentation because muscle retraction can occur and the muscle can adhere to the femur (tendon cannot be mobilized).
    • Quadriceps sets and straight-leg raises in a knee immobilizer are begun immediately after surgery.
Physical Therapy
  • Therapy is best begun early, 1-2 weeks after repair.
  • Passive ROM and active flexion exercises are emphasized.
  • May wean from use of the knee brace with improved quadriceps strength (6-8 weeks)
  • NSAIDs are helpful for reducing swelling and pain.
  • Narcotics may be added for analgesia.
  • Primary end-to-patella repair:
    • Results are better with early intervention.
    • Delayed repairs may require augmentation or interpositional tendon graft.
  • Results are excellent with appropriate treatment.
  • ~90% of patients achieve full or near-full ROM and full or near-full return of preinjury strength.
  • Extensor lag
  • Extension weakness
  • Tendon rerupture
Patient Monitoring
Patients are followed at 1-month intervals until they attain full ROM and strength, and normal gait and function.
844.8 Quadriceps tendon rupture
Patient Teaching
  • Chronic quadriceps tendinitis should not be ignored because it puts the tendon at risk for rupture with a sudden misstep.
  • After surgical repair, patients can recover full motion, strength, and function with an intensive physical therapy program.
Q: Is quadriceps tendon rupture the only mechanism for losing the ability to extend a flexed knee?
A: The extensor mechanism includes the quadriceps muscles, quadriceps tendon, patella, and patellar tendon. All are required to extend the knee forcefully or to perform a straight-leg raise. A rupture of the quadriceps or patellar tendon or a fracture of the patella will make extending the knee difficult.

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