The knee extensor mechanism includes:

• Patellar Tendon: Connects the bottom of the kneecap to the shinbone.
• Quadriceps Tendon: Connects the quadriceps muscle (front of the thigh) to the top of the kneecap.
• Quadriceps Muscle Group: The muscles on the front of the thigh.
• Patella (Kneecap): The bone that sits in front of the knee joint.

These parts work together to help extend (straighten) the knee and keep it stable and allow you to walk without your knee giving out.

A patellar tendon rupture is when the patellar tendon tears off the bottom of the kneecap, either completely or partially. This injury affects the tendon that helps you straighten your knee. If the tendon is ruptured, you might have trouble straightening your leg, walking, running, or jumping.

• Sudden, Powerful Movements: Such as a fall, jumping, landing, or making sudden stops.
• Chronic Overuse: Repeated stress or strain over time, especially in older people.

Symptoms of a Patellar Tendon Rupture

• Severe pain in the front of the knee, often below or around the kneecap.
• Swelling of the knee.
• Difficulty straightening the knee or lifting your leg.
• Trouble bearing weight on the leg.
• A noticeable gap or dent just below the kneecap.
• The kneecap might move up higher than it normally sits.

To diagnose a patellar tendon injury, doctors usually perform the following:

1. Physical Examination: Checking for gaps or dents in the tendon, testing your ability to straighten your leg and seeing if you can hold it without bending your leg.
2. X-rays: To rule out fractures and see if the kneecap has moved up higher than where it normally sits (a condition called patella alta).
3. MRI: To see the extent of the tendon injury and check for any other damage to ligaments, menisci, or cartilage.