The patellar tendon runs from the lower part of the patellar to the tibia (lower leg bone.) It attaches the quadriceps muscle to the lower leg and transfers the forces of the quadriceps. This allows for knee extension or straightening. Patellar tendon rupture is rare and usually occurs in individuals below the age of 40 as a result of an athletic injury.
Common causes of patellar tendon rupture include:
- The progression of or the final result of longstanding patellar tendonitis or an overuse injury.
- A heavy load of weight or stress is applied while the foot is planted and the knee is bent. This is common while landing from a jump, for example while playing basketball.
- A sudden deceleration or stopping motion can sometimes rupture the patellar tendon.
- Injection of steroids to the patellar tendon or the excessive use of steroids has been known to weaken the tendon and make it susceptible to rupture.
- An injury or direct blow to the patellar tendon.
- Laceration of the patellar tendon.
- Certain systemic diseases have been associated with patellar tendon weakness.
- Patellar tendon ruptures can also occur as post surgical complications (for example following an ACL reconstruction or a total knee replacement.)
- Immediate pain at time of injury.
- A loud audible pop at the time of injury.
- Swelling and bruising or ecchymosis is present in the front of the knee.
- There is a gap where the tendon has ruptured
- It is difficult to put weight on the leg.
- Inability to straighten the knee actively by yourself.
