Tibial tuberosity avulsion

A tibial tuberosity avulsion usually happens suddenly during physical activity. Common symptoms include: 

• Sudden, sharp pain at the front of the knee, just below the kneecap
• A popping or tearing sensation at the time of injury
• Swelling around the top of the shin
• Tenderness over the tibial tuberosity
• Difficulty or inability to straighten the knee
• Trouble walking, running or bearing weight on the affected leg 

Pain and swelling often increase in the hours following the injury, and weakness with knee extension typically continues until the fracture is properly treated.

A tibial tuberosity avulsion fracture happens when the force from the quadriceps muscle pulling through the patellar tendon becomes too great for the growth plate to handle. Common causes include: 

• Jumping activities, such as basketball or volleyball
• Sprinting or sudden acceleration
• Forceful landing after a jump
• A quick, powerful contraction of the thigh muscles during sports 

This injury most often occurs in adolescent boys during their growth spurt, when the growth plate at the tibial tuberosity is beginning to close but is still weaker than the surrounding bone. 

Certain factors can make a tibial tuberosity avulsion more likely, though having one or more of these does not mean an injury will occur: 

• Participation in jumping sports, such as basketball, volleyball or track and field
• Being in the adolescent growth spurt, typically between ages 12 and 15 for boys
• A history of Osgood-Schlatter disease, which can weaken the tibial tuberosity over time
• Rapid increases in training intensity without adequate conditioning 

Your child's care team can help assess individual risk and recommend safe return-to-play guidelines. 

Diagnosing a tibial tuberosity avulsion starts with a discussion of how the injury happened and a physical examination of the knee to check for swelling, tenderness and range of motion. X-rays are typically used to confirm the fracture and determine how much the bone fragment has shifted. In some cases, a CT scan or MRI may be recommended to get a more detailed look at the fracture pattern or to check for related injuries before planning treatment.