If you can’t fully straighten your knee after a fall, awkward landing, or sports injury, it’s important to get it checked out quickly. You might have a torn tendon, but swelling, a kneecap injury, or tissue caught in the joint can also make it hard to move. Trying to force your knee straight won’t tell you what’s wrong.
At Jonathan L. Glashow, MD Orthopedic Surgery & Sports Medicine on the Upper East Side, you can get your knee injury evaluated quickly, with same-day imaging available when you need it.
Why Can an Injured Knee Refuse to Straighten?
Two different problems can feel a lot alike. Sometimes, something inside your knee joint blocks normal movement. A torn meniscus can cause catching, locking, and make it hard to move your knee, as the American Academy of Orthopaedic Surgeons explains.
You might also find you can’t straighten your leg because the extensor mechanism isn’t working. The quadriceps tendon connects your thigh muscles to the top of your kneecap, and the patellar tendon connects your kneecap to your shinbone. If you have a complete quadriceps tendon tear or patellar tendon rupture, that connection is lost.
Which Signs Point Toward a Tendon Rupture?
A rupture usually happens when a bent knee takes a sudden load, like landing from a jump or trying to stop a fall. You might notice:
- A pop or tearing sensation at the front of the knee
- Rapid swelling or bruising
- A gap above or below the kneecap
- Buckling when you try to stand
- Inability to lift the straight leg or hold the knee extended
According to the AAOS, a complete quadriceps tendon tear usually means you can’t actively straighten your knee. Pain alone can also make it hard to use your quadriceps, so you’ll still need an orthopedic exam to know for sure.
How Do We Separate a Tear from Another Injury?
We’ll talk with you about how the injury happened, check your kneecap, and see if you can straighten your leg on your own. X-rays help us spot fractures or changes in kneecap position, while an MRI can show how much of the tendon is torn or if there’s another soft-tissue injury.
If you have a small partial tear and your extensor mechanism still works, bracing and rehab may be enough. A complete tear usually means you’ll need quadriceps and patellar tendon repair surgery to reconnect the tendon near your kneecap. Getting checked early matters, since a fully torn tendon can pull back and scar, which makes later repairs harder.
Dr. Jonathan L. Glashow is a board-certified orthopedic surgeon and Clinical Associate Professor in the Department of Orthopedic Surgery at NYU Grossman School of Medicine. He’ll recommend the right treatment for you based on your injury, imaging results, tendon quality, and what you need your knee to do.
Frequently Asked Questions
Can you still walk with a torn quadriceps or patellar tendon?
Some people can take a few steps, but the knee may buckle, and walking doesn’t rule out a serious tear. Avoid repeatedly testing the injured leg and arrange an evaluation.
Does every knee that won’t straighten need surgery?
No. The right treatment depends on whether your knee is stiff from pain, swelling, a mechanical block, a partial tear, or a complete rupture. Your exam and imaging will help us decide what makes sense for you.
Arrange an Urgent Knee Evaluation in NYC
If you can’t straighten your knee after an injury, waiting to get checked can limit your treatment choices. Reach out to our Upper East Side office for an exam and, if needed, same-day imaging. We’ll help you figure out if you need protection and rehab or quadriceps or patellar tendon repair in NYC.
