Tendons attach muscles to bones. The patellar tendon attaches the bottom of the kneecap (patella) to the top of the shinbone (tibia). It is actually a ligament that connects to two different bones, the patella and the tibia.
Patellar tendon tears can be either partial or complete.
Partial tears. Many tears do not completely disrupt the soft tissue. This is similar to a rope stretched so far that some of the fibers are torn, but the rope is still in one piece.
Complete tears. A complete tear will disrupt the soft tissue into two pieces.
A very strong force is required to tear the patellar tendon.
Falls. Direct impact to the front of the knee from a fall or other blow is a common cause of tears. Cuts are often associated with this type of injury.
Jumping. The patellar tendon usually tears when the knee is bent and the foot planted, like when landing from a jump or jumping up.
A weakened patellar tendon is more likely to tear. Several things can lead to tendon weakness.
Patellar tendonitis. Inflammation of the patellar tendon, called patellar tendonitis, weakens the tendon. It may also cause small tears.
Patellar tendonitis is most common in people who participate in activities that require running or jumping. While it is more common in runners, it is sometimes referred to as “jumper’s knee.”
Corticosteroid injections to treat patellar tendonitis are typically avoided in or around the infrapatellar tendon. Injections around this articular tendon have been linked to increased tendon weakness and increased likelihood of tendon rupture.
Chronic disease. Weakened tendons can also be caused by diseases that disrupt blood supply. Chronic diseases which may weaken the tendon include:
- Chronic renal failure
- Hyper betalipoproteinemia
- Rheumatoid arthritis
- Systemic lupus erythmatosus (SLE)
- Diabetes mellitus
- Metabolic disease
Steroid use. Using medications like corticosteroids and anabolic steroids has been linked to increased muscle and tendon weakness.
When a patellar tendon tears there is often a tearing or popping sensation. Pain and swelling typically follow. Additional symptoms include:
- An indentation at the bottom of your kneecap where the patellar tendon tore
- Your kneecap may move up into the thigh because it is no longer anchored to your shinbone
- You are unable to straighten your knee
- Difficulty walking due to the knee buckling or giving way
Your doctor will discuss your medical history. Questions you might be asked include:
- Have you had a previous injury to the front of your knee?
- Do you have patellar tendonitis?
- Do you have any medical conditions that might predispose you to a quadriceps injury?
- Have you had surgery to your knee, such as a total knee replacement or an anterior cruciate ligament reconstruction?
To determine the exact cause of your symptoms, Dr. Backe will test how well you can extend, or straighten, your knee. While this part of the examination can be painful, it is important to identify a patellar tendon tear.
To confirm the diagnosis, Dr. Backe may order some imaging tests, such as an X-ray or magnetic resonance imaging (MRI) scan.
X-rays. The kneecap moves out of place when the patellar tendon tears. This is often very obvious on a “sideways” X-ray view of the knee. Complete tears can often be identified with these X-rays alone.
MRI. This scan creates better images of soft tissues like the patellar tendon. The MRI can show the amount of tendon torn and the location of the tear. Sometimes, an MRI is required to rule out a different injury that has similar symptoms.
If you have been diagnosed with a patellar tendon tear, you should go to an orthopaedic surgeon for treatment.
The type of treatment you require will depend on several things:
- The type and size of tear you have
- Your activity level
- Your age
Very small, partial tears respond well to nonsurgical treatment.
Immobilization. Your doctor may recommend you wear a knee immobilizer or brace. This will keep your knee straight to help it heal. You will most likely need crutches to help you avoid putting all of your weight on your leg. You can expect to be in a knee immobilizer or brace for 3 to 6 weeks.
Physical therapy. Specific exercises can restore strength and range of motion.
While you are wearing the brace, Dr. Backe may recommend exercises to strengthen your quadriceps muscles. Straight-leg raises are often prescribed. As time goes on, Dr. Backe or therapist will unlock your brace. This will allow you to move more freely with a greater range of motion. You will be prescribed more strengthening exercises as you heal.
Most people require surgery to regain the most function in their leg. Surgical repair reattaches the torn tendon to the kneecap.
People who require surgery do better if the repair is performed early after the injury. Early repair may prevent the tendon from scarring and tightening in a shortened position.
To reattach the tendon, sutures are placed in the tendon and then threaded through drill holes in the kneecap. The sutures are tied at the top of the kneecap.Your surgeon will carefully tie the sutures to get the correct tension in the tendon. This will also make sure the position of the kneecap closely matches that of your uninjured kneecap.