The patellar tendon connects the kneecap (patella) to the tibia and is the terminal attachment of the quadriceps mechanism that extends the knee. A patellar tendon rupture is a complete or partial tear of this tendon, typically from a forceful eccentric contraction of the quadriceps against a flexed knee. The injury produces immediate loss of active knee extension and requires timely surgical repair for the best outcomes.
What Is a Patellar Tendon Rupture?
The quadriceps muscle attaches to the top of the patella through the quadriceps tendon. The patella then connects to the tibia through the patellar tendon, which inserts at the tibial tubercle. Together, this quadriceps-patella-patellar tendon unit is the extensor mechanism of the knee: the system that straightens the knee and resists the knee from buckling under load.
A patellar tendon rupture disrupts this chain. The most common tear location is at the inferior pole of the patella, where the tendon inserts into the bone. Midsubstance and tibial tubercle avulsion patterns occur less often. Once torn, the tendon does not heal back to bone on its own, and the retracted tendon makes repair progressively more difficult with time.
Patellar tendon rupture tends to occur in younger patients (typically under 40) and patients with tendon degeneration from prior injury, chronic patellar tendinosis, or systemic factors.
Causes and Risk Factors
- Forceful quadriceps contraction with the knee flexed (landing from a jump, stepping off a curb, weightlifting)
- Prior patellar tendinosis, which weakens the tendon
- Prior patellar tendon injury or surgery
- Corticosteroid injection into or around the tendon
- Systemic factors: diabetes, chronic renal disease, rheumatologic conditions, fluoroquinolone antibiotic use
- Anabolic steroid use
- Sports with jumping and explosive loading (basketball, volleyball, weightlifting)
Symptoms
- Immediate pain at the front of the knee during the injury
- A felt or heard pop at the time of rupture
- Inability to actively extend the knee or maintain a straight leg against gravity
- High-riding patella on inspection, with a palpable gap below the kneecap
- Swelling and bruising over the anterior knee
- Difficulty or inability to walk without assistance
Diagnosis
Dr. Chudik’s evaluation includes the mechanism, the timing, and a physical examination focused on active knee extension. The hallmark finding is loss of active knee extension with a palpable gap at the inferior pole of the patella. X-rays show a patella that has migrated proximally (patella alta) and may show an avulsion fragment. MRI confirms the tear location and extent and is used when physical examination is equivocal. The Westmont office has on-site high-field MRI and X-ray.
Treatment
Non-surgical treatment is reserved for partial tears in which active knee extension is preserved. It involves bracing in extension for several weeks, progressive range of motion, and quadriceps strengthening.
For complete tears, Dr. Chudik performs patellar tendon repair as soon as possible after injury. The torn tendon is reattached to the inferior pole of the patella with suture anchors or bone tunnels, with suture augmentation that protects the repair during early motion. Chronic or retracted tears may require a tendon graft to bridge the defect.
Recovery and Outcomes
Recovery after acute patellar tendon repair typically includes six weeks of brace protection in extension with progressive range of motion, active extension starting at four to six weeks, progressive strengthening over three to four months, and return to sport at six to nine months. Return to jumping sport is typically nine to 12 months.
Outcomes after acute repair are generally good, with most patients regaining active knee extension and functional strength. Chronic or retracted repairs have more variable outcomes and a higher rate of persistent quadriceps weakness.
When to See Dr. Chudik
Schedule an evaluation urgently after any knee injury that produces inability to straighten the knee or lift a straight leg. This is a time-sensitive injury. Call 630-324-0402 or request an appointment online.