Knee

Patellar Tendon Rupture

A patellar tendon rupture is a serious disruption of the knee's extensor mechanism, the force-transmission system that allows you to straighten your leg against gravity. While less common than quadriceps tendon rupture, patellar tendon tears occur predominantly in patients under 40, often in athletes undergoing forceful eccentric quadriceps loading. Prompt diagnosis and surgical repair within two to three weeks of injury produce substantially better outcomes than delayed treatment. At Maryland Orthopedic Specialists, our surgeons are experienced in both acute primary repair and the more challenging reconstruction required for chronic or attritional tears.

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What is patellar tendon rupture?

The patellar tendon connects the inferior pole of the patella to the tibial tubercle and, along with the quadriceps tendon and patella, forms the extensor mechanism of the knee. A rupture most commonly occurs at the distal pole of the patella (the tendon's patellar origin), where repetitive microtrauma may have compromised tendon integrity even before an acute event.

The patellar tendon connects the inferior pole of the patella to the tibial tubercle and, along with the quadriceps tendon and patella, forms the extensor mechanism of the knee. A rupture most commonly occurs at the distal pole of the patella (the tendon's patellar origin), where repetitive microtrauma may have compromised tendon integrity even before an acute event.

Injury mechanisms include:

Forceful eccentric quadriceps contraction (landing from a jump, stumbling on stairs)
Direct laceration or trauma to the anterior knee
Forceful passive knee flexion against contracted quadriceps
Attritional failure in patients with pre-existing tendinopathy

Risk factors for spontaneous or attritional rupture include prior patellar tendinitis, corticosteroid injections into the tendon, systemic conditions (renal failure, diabetes, lupus, rheumatoid arthritis), fluoroquinolone antibiotic use, and anabolic steroid use.

Tears are classified as:

Partial: incomplete fiber disruption; active extension preserved
Complete: full-thickness tear; loss of active extension against gravity

Symptoms — do you recognize these?

Sudden onset of anterior knee pain at the moment of injury
A "pop" felt or heard at injury
Inability to perform a straight-leg raise — the hallmark of complete rupture; the patient cannot extend the knee against gravity
Visible or palpable gap inferior to the patella
Patella alta — the patella migrates superiorly as the distal tether is lost; visible on lateral X-ray
Rapid swelling and ecchymosis over the anterior knee
Antalgic gait; inability to bear weight normally

Call us at (301) 515-0900. Same-day appointments available at our Bethesda and Germantown locations.

How we diagnose it

Physical Examination

Straight-leg raise test: failure to actively extend against gravity confirms complete extensor disruption
Palpation of a soft-tissue defect below the inferior pole of the patella
High-riding patella observed clinically

Imaging

X-ray (lateral view): patella alta is the cardinal radiographic sign; the Insall-Salvati ratio (patellar tendon length to patellar length) exceeds 1.2; avulsion fragments from the tibial tubercle or patellar tip may be visible
Ultrasound: dynamic, cost-effective; directly visualizes tendon discontinuity, fiber disruption, and hematoma; allows real-time assessment
MRI — definitive characterization of tear extent, location, tendon quality (degeneration, partial tears), and associated injuries (meniscal, ligamentous, chondral); essential for pre-operative planning for chronic or complex tears

Treatment options

Acute patellar tendon ruptures are surgical emergencies. Repair within 2–3 weeks is essential to prevent the retraction and scarring that make later reconstruction far more complex. The treatment approach depends on the completeness of the tear, the time elapsed since injury, and the quality of the remaining tendon tissue.

Non-Operative Management

Conservative treatment is appropriate only for partial tears involving less than 50% of the tendon cross-sectional area in patients who retain active knee extension without a functional extensor lag. These patients are treated with a cylinder cast or knee immobilizer held in full extension for 4–6 weeks, followed by a supervised rehabilitation program to restore range of motion and quadriceps strength.

Rehabilitation

Following surgical repair, patients are maintained non-weight-bearing in an extension brace for the first 6 weeks to protect the repair, after which progressive weight-bearing and physical therapy with gradual range-of-motion advancement are begun. Return to sport for athletes with uncomplicated acute repairs is expected at 9–12 months, contingent on meeting strength symmetry and functional testing criteria.

Surgical Procedure

Patellar Tendon Repair

Urgent surgical reattachment of a completely ruptured patellar tendon to the inferior pole of the patella. Restoring correct tendon length and extensor mechanism continuity is critical. Delayed repair significantly worsens outcomes.

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Recovery & rehabilitation

0–2 weeks: Knee immobilizer or cylinder cast; toe-touch weight-bearing; quadriceps sets
2–6 weeks: Progressive weight-bearing; supervised range-of-motion to 90°
6–12 weeks: Closed-chain strengthening; stationary cycling
3–6 months: Running, sport-specific training for athletes
6–12 months: Return to competitive sport after meeting strength (> 90% limb symmetry index) and functional testing criteria

Chronic repairs and reconstructions follow a longer timeline due to graft incorporation and the greater initial tissue deficit.

Frequently Asked Questions

How urgent is surgery for a patellar tendon rupture?

Complete tears should be repaired within two to three weeks of injury. After this window, the quadriceps muscle shortens and scars, making it progressively harder to restore the patella to its normal position and achieve full extension. Outcomes are significantly better with early repair.

Can I walk with a patellar tendon rupture?

Patients with complete tears cannot extend the knee against gravity and typically cannot walk normally without a locked brace. Partial tears with preserved active extension may allow limited ambulation.

Will I regain full function after repair?

Most patients who undergo timely primary repair regain full or near-full range of motion and return to their pre-injury activity level. Return to high-demand athletics is expected by 9–12 months in athletes with uncomplicated repairs.

What causes patellar tendon rupture in younger patients without trauma history?

Subclinical patellar tendinopathy (tendon degeneration) is present in a high proportion of "spontaneous" ruptures at autopsy. Chronic overuse, corticosteroid injections, and systemic metabolic conditions weaken tendon collagen architecture before a seemingly minor event causes complete failure.

How long does recovery take after patellar tendon repair, and when can I return to sport?

Recovery after patellar tendon repair is a prolonged process that typically takes nine to twelve months before return to sport. The repaired tendon is protected in a brace for the first four to six weeks, with gradual restoration of knee flexion thereafter. Quadriceps strengthening is a central focus of rehabilitation, as the muscle often atrophies significantly during the protected phase. Your MOS surgeon will monitor tendon integrity and guide your progression through functional milestones, ensuring the repair is mature enough before high-demand activities are attempted.