Knee Extensor Injuries
(Quadriceps Tendon Tear; Patellar Tendon Tear; Patellar Fracture; Tibial Tubercle Fracture)
Knee extensor injuries occur when people try to straighten (extend) their knee and an obstacle prevents them from doing so. Such injuries can tear the tendon that attaches the main muscle in the thigh (quadriceps) to the kneecap (patella), tear the tendon that attaches the kneecap to the shinbone (tibia), or break the kneecap or top of the shinbone.
In healthy people, knee extensor injuries occur only when force is significant (as occurs in a jump from a height or in high-impact car crashes). However, people may have certain conditions that make these injuries more likely. These conditions include older age, osteoarthritis, and use of certain drugs (such as corticosteroids or antibiotics called fluoroquinolones). People with one of these conditions can injure their knee when they stumble on stairs or catch their foot when walking.
Extending the Knee
Extending the knee involves several structures, which can be injured when people try to straighten their knee and are blocked from doing so. These injuries include