The quadriceps tendon connects the quadriceps muscle to the top of the patella and is part of the extensor mechanism that straightens the knee. Quadriceps tendon ruptures are the most common extensor mechanism injury in patients over 40 and typically result from a forceful eccentric quadriceps contraction. The injury produces loss of active knee extension and requires timely surgical repair.
What Is a Quadriceps Tendon Rupture?
The quadriceps muscle (four muscle bellies: rectus femoris, vastus medialis, vastus intermedius, vastus lateralis) converges into a single tendon that inserts on the superior pole of the patella. This tendon is part of the extensor mechanism of the knee.
Quadriceps tendon rupture most commonly occurs at or near the attachment to the patella, where the tendon tissue has the highest mechanical stress and the lowest vascular supply. Complete ruptures produce immediate loss of active knee extension. Partial ruptures preserve some extension but produce weakness and often an extension lag.
Quadriceps rupture is more common in patients over 40 and typically occurs in tendons that have some degree of pre-existing tendinosis.
Causes and Risk Factors
- Forceful eccentric contraction of the quadriceps, often with the knee flexed during a fall or stumble
- Age over 40, with increasing prevalence through the sixth and seventh decades
- Male sex
- Systemic factors: diabetes, chronic kidney disease, gout, rheumatoid arthritis
- Fluoroquinolone antibiotic use and corticosteroid injection
- Obesity
- Prior tendinosis or tendon degeneration
- Bilateral rupture occurs in about 10 percent and suggests an underlying systemic factor
Symptoms
- Sharp pain above the kneecap during a fall or forceful quadriceps contraction
- A pop or tearing sensation at the time of injury
- Inability to extend the knee or lift the leg against gravity with the knee straight
- Palpable gap above the patella
- Low-riding patella (patella baja) on inspection
- Swelling and bruising over the anterior thigh and knee
- Inability to walk without assistance
Diagnosis
Dr. Chudik’s evaluation includes the mechanism, timing, and a physical examination focused on the extensor mechanism. Loss of active knee extension with a palpable gap above the patella is diagnostic. X-rays show a low-riding patella and may show avulsion fragments. MRI confirms the tear and is used when examination is equivocal or the tear pattern affects surgical planning. 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 brace immobilization in extension for several weeks, progressive range of motion, and quadriceps strengthening.
For complete tears, Dr. Chudik performs quadriceps tendon repair as soon as possible after injury. The torn tendon is reattached to the superior pole of the patella with suture anchors or bone tunnels. Suture augmentation protects the repair during early motion. Chronic or retracted tears may require tendon advancement techniques or allograft augmentation.
Recovery and Outcomes
Recovery after acute quadriceps tendon repair typically includes four to six weeks of brace protection in extension with progressive range of motion, active extension beginning at four to six weeks, progressive strengthening over three to four months, and return to daily activity at three to four months. Return to sport is typically six to nine months.
Outcomes are generally good with acute repair. Chronic repairs have more variable outcomes and a higher rate of persistent quadriceps weakness and extension lag. Age and systemic health factors also affect outcomes.
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.