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.
The patella is attached to the quadriceps muscles by the quadriceps tendon. Working together, the quadriceps muscles, quadriceps tendon and patellar tendon straighten the knee.
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.
The patellar tendon often tears where it attaches to the kneecap, and can break a piece of the bone as it tears. When the patellar tendon is completely torn, the tendon is separated from the kneecap. Without this attachment, you cannot straighten your knee.
When a tear is caused by a medical condition — like tendonitis — the tendon usually tears in the middle.
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.<
- 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
- 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.
- Hospital stay. Tendon repairs are sometimes done on an outpatient basis. Most people do stay in the hospital at least one night after this operation. Whether or not you will need to stay overnight will depend on your medical needs.
The surgery may be performed with regional (spinal) anesthetic or with a general anesthetic (breathing tube). It cannot be done under local anesthesia.
- Procedure. 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.
- New Technique. A recent development in patellar tendon repair is the use of suture anchors. Surgeons use anchors to sew the tendon to the bottom of the kneecap. Using these anchors means that drill holes in the kneecap are not necessary. This is a new technique, so data is still being collected on its effectiveness. Most orthopaedic research on patellar tendon repair involves the direct suture repair with the drill holes in the kneecap.
Previous surgery around the tendon, such as a total knee replacement or anterior cruciate ligament reconstruction, might put you at greater risk for a tear.
When a patellar tendon tears there is often a tearing or popping sensation. Pain and swelling typically follow. Additional symptoms include:
Very small, partial tears respond well to nonsurgical treatment.
While you are wearing the brace, your doctor may recommend exercises to strengthen your quadriceps muscles. Straight-leg raises are often prescribed. As time goes on, your doctor 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.