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Knee

Patellar Tendon Ruptures

What is a Patellar Tendon Rupture?

A patellar tendon rupture is a serious injury in which the tendon that connects the kneecap (patella) to the shinbone (tibia) becomes partially or completely torn. This tendon works together with the quadriceps muscle and quadriceps tendon to allow the leg to straighten and support walking, running, and jumping.

When the patellar tendon tears, patients lose the ability to actively straighten the knee, making it extremely difficult to walk, climb stairs, or bear weight. This injury typically occurs in active adults under 50 years old, often during sports or a sudden fall, and requires prompt diagnosis and treatment to restore normal function.

The extensor mechanism of the knee includes three key components:

  1. The quadriceps muscles in the front of the thigh.
  2. The quadriceps tendon, which connects the quadriceps muscle to the patella (kneecap).
  3. The patellar tendon, which attaches the bottom of the patella to the tibia (shinbone).

Together, this system allows you to straighten your knee and stabilize the leg when standing or landing. When the patellar tendon is torn, the chain is disrupted, and the knee loses the ability to extend against gravity.

Patellar tendon ruptures often occur when a person lands awkwardly from a jump, stumbles, or tries to catch themselves from a fall while the knee is bent. The tendon fails as the quadriceps muscle contracts forcefully to straighten the leg against resistance.

Common Causes and Risk Factors

  • Sudden deceleration or landing injury (basketball, volleyball, soccer).
  • Direct trauma to the front of the knee.
  • Degenerative changes from chronic tendinitis or overuse.
  • Systemic conditions that weaken tendons, including diabetes, kidney disease, or lupus.
  • Anabolic steroid or fluoroquinolone use, which can impair tendon strength.

Patellar tendon ruptures can occur in otherwise healthy individuals but are more likely in patients with preexisting tendon inflammation or degeneration.

Typical symptoms include:

  • Sudden pain at the front of the knee or just below the kneecap.
  • Swelling and bruising shortly after injury.
  • A palpable gap below the patella where the tendon has torn.
  • Inability to straighten the leg or perform a straight-leg raise.
  • The kneecap appearing higher than normal (patella alta) due to loss of the lower tendon attachment.

Patients often describe feeling a “pop” at the time of injury, followed by immediate weakness and difficulty walking.

Diagnosis begins with a detailed history and physical examination by Dr. José Vega, Cleveland’s trusted orthopedic knee specialist.

During your evaluation, Dr. Vega will:

  • Check for swelling and a visible gap below the kneecap.
  • Assess knee alignment and ability to straighten the leg.
  • Compare the position of both kneecaps for asymmetry.

Imaging Studies

  • X-rays may show a high-riding patella (patella alta), suggesting complete tendon rupture.
  • Ultrasound can confirm a discontinuity in the tendon fibers.
  • MRI provides detailed visualization of the tear, the degree of retraction, and the quality of the remaining tissue—information critical for planning surgical repair.

Partial tears may be treated nonsurgically if some tendon fibers remain intact and the patient can still extend the knee.

Nonsurgical management includes:

  • Immobilization in a knee brace or cast for 4–6 weeks in full extension.
  • Physical therapy after immobilization to restore range of motion and strength.

However, complete ruptures require surgery for functional recovery. Without repair, the knee cannot straighten properly, leading to chronic weakness and disability.

Surgery is indicated for all complete patellar tendon ruptures and should ideally be performed within 2–3 weeks of injury for the best results. Early repair reduces scarring and allows for stronger tendon reattachment.

The surgery is performed through an incision at the front of the knee.

Surgical Steps

  • The torn ends of the tendon are identified and cleaned.
  • The tendon is reattached to the bottom of the patella using strong sutures passed through bone tunnels or suture anchors.
  • If the tendon is severely damaged, augmentation with a tissue graft (usually from a cadaver) may be performed for reinforcement.
  • The knee is then placed in a brace to protect the repair while healing begins.

Modern techniques and suture materials have significantly improved the strength and reliability of patellar tendon repairs.

Rehabilitation is essential for successful recovery and involves gradual, supervised progression through the following phases:

  • Weeks 0–6: Knee immobilized in extension. Early passive motion is introduced as healing allows.
  • Weeks 6–12: Gradual increase in motion and light strengthening exercises.
  • 3–6 months: Progressive strengthening and return to daily activities.
  • 6–9 months: Return to full sport or physically demanding work.

Physical therapy focuses on restoring quadriceps strength, knee range of motion, and proprioception, while avoiding excessive stress on the repair during early healing.

Most patients recover full function and return to previous activity levels when rehabilitation is followed closely.

While not all injuries can be prevented, you can reduce risk by:

  • Maintaining flexibility and strength in the quadriceps and hamstrings.
  • Warming up and stretching before activity.
  • Treating chronic patellar tendinitis early to prevent weakening of the tendon.
  • Avoiding overuse and allowing adequate recovery between training sessions.
  • Monitoring medication use that may affect tendon integrity.

A patellar tendon rupture is a disabling but highly treatable injury. With early diagnosis, expert surgical repair, and guided rehabilitation, patients can expect to regain full strength and function. If you experience sudden knee pain, swelling, or difficulty straightening your leg after an injury, contact Dr. José Vega’s office in Cleveland today to schedule an evaluation and begin a personalized treatment plan.

References

  1. Siwek CW, Rao JP. Ruptures of the extensor mechanism of the knee joint: a review of 46 cases. J Bone Joint Surg Am. 1981;63(6):932–937.
  2. Clayton RA, Court-Brown CM. The epidemiology of musculoskeletal tendinous and ligamentous injuries. Injury. 2008;39(12):1338–1344.
  3. O’Dowd JA, Shields DW, Alvarez AM, et al. Outcomes following repair of acute patellar tendon ruptures: a systematic review and meta-analysis. Orthop J Sports Med. 2019;7(7):2325967119853776.
  4. Ettinger M, Dratzidis A, Hurschler C, et al. Biomechanical properties of different repair techniques for acute patellar tendon rupture: an experimental cadaveric study. Knee Surg Sports Traumatol Arthrosc. 2020;28(6):1895–1903.
  5. Enad JG, Loomis LL. Primary repair and early motion for patellar tendon rupture: a retrospective review. Mil Med. 2019;184(Suppl 1):500–504.
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Dr. Jose Vega

  • Board-certified orthopedic surgeon
  • Fellowship-trained sports medicine specialist
  • Author of industry leading peer reviewed publications
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