Patellar tendinitis is an injury to the tendon that joins the kneecap, also called the patella, to the shinbone. The patellar tendon works with the muscles at the front of the thigh to straighten the knee.

Patellar tendinitis also is called jumper's knee. It's most common in athletes whose sports involve a lot of jumping. Examples are basketball and volleyball. But people who don't play jumping sports also can get patellar tendinitis.

For most people, treatment of patellar tendinitis begins with physical therapy to strengthen the muscles that straighten the knee called the quadriceps muscles.

For knee pain, try self-care measures first. These include icing the area and reducing or not doing the activities that cause your symptoms for a time.

Call your doctor if your pain:

• Continues or gets worse.
• Keeps you from doing your daily activities.
• Is linked to swelling or redness about the knee joint.

Patellar tendinitis is a common injury caused by too much use. The repeated stress on the patellar tendon results in tiny tears in the tendon.

Repeated stress on the tendon without enough time to recover can lead to a weakened tendon. The body tries to heal the damage, which thickens the tendon.

A mix of factors may be part of getting patellar tendinitis. They include:

• Male sex. People assigned male at birth are more likely to get patellar tendinitis.
• Physical activity. Running and jumping most often are linked with patellar tendinitis. Training more than 20 hours a week for this type of impact exercises is a risk factor. Sudden increases in how hard or how often you do the activity also add stress to the tendon.
• Tight thigh muscles. Tight front-of-the-thigh muscles, called quadriceps, and tight back-of-the-thigh muscles, called hamstrings, can increase strain on your patellar tendon.
• Muscular that aren't balanced. If some muscles in your legs are much stronger than others, the imbalance could put strain on your patellar tendon. This uneven pull could cause tendinitis.
• Chronic illness. Some illnesses disrupt blood flow to the knee, which weakens the tendon. Examples include kidney failure, autoimmune diseases such as lupus or rheumatoid arthritis, and diseases such as diabetes that affect how the body uses food to make energy, called metabolic.

Working through the pain can cause more and larger tears in the patellar tendon. Rarely, the tendon can rupture.

Patellar tendinitis can keep athletes from returning to their sports.

To reduce your risk of developing patellar tendinitis, take these steps:

• Don't play through pain. As soon as you feel knee pain while exercising, rest and ice the area. Until your knee is pain-free, don't do activities that put stress on your patellar tendon.
• Strengthen your muscles. Strong front-of-the-thigh muscles can better handle the stresses that can cause patellar tendinitis. A type of exercise called eccentric involves lowering muscles slowly as you return to your start position. An example for the quadriceps muscles is slowly lowering a straight leg to a bent knee position while seated.
• Improve your form. Be sure to use the right form when doing an exercise or sport. You might take lessons or get help from a professional when you start a new sport or use exercise equipment.

During the exam, your healthcare professional may press on parts of your knee to find where you hurt. Often, pain from patellar tendinitis is on the front part of your knee, just below your kneecap.

Imaging tests

These tests are not always needed to diagnose patellar tendinitis. But your healthcare professional may suggest one or more of the following imaging tests:

• X-rays. X-rays help rule out other bone problems that can cause knee pain.
• Ultrasound. This test uses sound waves to create an image of your knee. The image can show tears in your patellar tendon.
• Magnetic resonance imaging (MRI). MRI uses a magnetic field and radio waves to create detailed images. These can show small changes in the patellar tendon.

Surgery is rarely needed for patellar tendinitis. Treatment often starts with limiting activities that cause the pain and some of the following:

Medicines

Pain relievers such as ibuprofen (Advil, Motrin IB, others) or naproxen sodium (Aleve, others) may provide short-term relief from pain associated with patellar tendinitis.

Physical therapy

These physical therapy techniques can help reduce the symptoms linked to patellar tendinitis:

• Stretching exercises. Regular, steady stretching exercises of the quadriceps and other muscles can help lengthen the muscle and tendon.
• Strengthening exercises. Weak thigh muscles put strain on your patellar tendon. Exercises that increase the load on the tendon little by little can build strength to protect the tendon.
• Strapping or taping These two methods can help take pressure off the patellar tendon. They may help relieve pain.
• Iontophoresis. This therapy involves putting a steroid medicine on your skin. A device then gives a low electrical charge to push the medicine through your skin.

Surgical and other procedures

If other treatments don't help, your healthcare professional may suggest other therapies, such as:

• Corticosteroid shot. A corticosteroid shot, called an injection, into the sheath around the patellar tendon may help relieve pain. A healthcare professional may use ultrasound to guide the shot to the right place. But these types of medicines are used with care because they can weaken tendons and make them more likely to tear.
• Platelet-rich plasma. This type of shot has been tried in some people with chronic patellar tendon problems. Studies are ongoing. The hope is that platelet-rich plasma will help heal the tendon.

• Oscillating needle procedure (Tenex) or water debridement (Tenjet). These procedures are done in an outpatient setting using a local numbing medicine. In the Tenex procedure, your healthcare professional uses ultrasound imaging to guide a small needle that moves back and forth, called oscillating. The needle cuts away the damaged area while sparing healthy tendon.

  In the Tenjet procedure, water is used to remove damaged tissue. Both procedures need more study. But results have shown promise.

• Surgery. In rare cases, if other treatments fail, your healthcare professional might suggest surgery. The surgery removes damaged tissue, called debridement, from the patellar tendon. Some procedures can be done through small cuts around the knee.

If your knee hurts, you might try the following:

• Pain relievers. Medicines you can get without a prescription might give short-term relief. These include ibuprofen (Advil, Motrin IB, others) and naproxen sodium (Aleve, others). These medicines in cream or gel form that you put on the skin can work as well with fewer side effects.
• Not moving in ways that cause pain. You may need to not do activities that cause or worsen the pain. You also might need to practice your sport less often or switch to a lower impact sport for a time. Working through pain can cause more damage to your patellar tendon.
• Ice. Apply ice after activity that causes pain. Place ice in a plastic bag and wrap the bag in a towel. Or try an ice massage. Freeze water in a plastic foam cup and hold the cup as you put the ice on your skin.

If you have knee pain during or after physical activity that doesn't get better with ice or rest, see your healthcare professional. After an exam, your healthcare professional might send you to a sports medicine specialist.

Here's information to help you get ready for your appointment.

What you can do

Make a list of:

• Your symptoms and when they began.
• Key medical information, including other conditions you have and medicines, vitamins and supplements you take. Include the doses and how often you take them.
• Your typical daily activity, including how long and hard you exercise and what types of exercise you do. Note if you've recently changed your activity, your activity level or your equipment, such as running shoes.
• Recent injuries that may have damaged your knee joint.
• Questions to ask your healthcare professional.

Here are some basic questions to ask about possible patellar tendinitis.

• What is the most likely cause of my symptoms?
• What tests do I need?
• What treatment do you suggest?
• With treatment, will I be able to go back to my sport? How long will treatment take?
• What exercise can I do while healing, if any?
• What self-care measures should I take?
• Should I see a specialist?

What to expect from your doctor

Your healthcare professional is likely to ask you questions, including:

• Are your symptoms getting worse?
• What activities cause your pain?
• How bad is your pain?
• What strength or stretching exercises do you do?
• Does your pain occur before, during or after your workouts? Or do you have it all the time?
• Is your knee swelling, locking or buckling?
• Do your symptoms make it hard for you to exercise, climb stairs or do other activities?
• What at-home treatments have you tried? What, if anything, has helped?