The plica is a fold in the membrane surrounding your knee joint. Your knee joint is surrounded by a fluid-filled capsule called the synovial membrane.

During the fetal stage you have three capsules, called the synovial plicae, that grow around the developing knee joint. These are usually absorbed before birth. However, in one study from 2006, 95 percent of people undergoing arthroscopic surgery had some remnant of the synovial plicae.

Plica syndrome happens when one of your plica is inflamed, usually due to an injury. This often happens in the middle of your kneecap, which is known as medial plica syndrome.

The main symptom of plica syndrome is knee pain, but many other conditions can cause this as well. Pain related to plica syndrome is usually:

  • achy, rather than sharp or shooting
  • worse when using stairs, squatting, or bending

Additional symptoms of plica syndrome include:

  • a catching or locking sensation in your knee when getting up from a chair after sitting for a long time
  • trouble sitting for long periods of time
  • a clicking or cracking sound when you bend or extend your knee
  • a feeling that your knee is giving out
  • a feeling of instability on stairs and slopes

You may even be able to feel your swollen plica when you press on your knee cap.

Plica syndrome is usually caused by stressing or overusing your knee. This is often caused by exercises that require you to frequently bend and straighten your knee, such as running, biking, or using a stair-climbing machine.

An injury from an accident, such as a fall or car accident, can also cause plica syndrome.

To diagnose plica syndrome, your doctor will start with a physical exam. They’ll use the exam to rule out any other possible causes of your knee pain, such as:

Make sure to tell your doctor about the sports you play or exercise routines you do, in addition to any recent accidents or injuries.

They may also use an MRI scan or X-ray to get a better look at your knee.

Most cases of plica syndrome respond well to physical therapy or a home exercise program. These usually involve stretching your hamstrings and strengthening your quadriceps. Most people start to feel relief within six to eight weeks of starting a physical therapy or exercise program.

Quadriceps strengthening

The medial plica is indirectly attached to your quadriceps, a large muscle in your thighs. If your quadriceps are weak, you’re more likely to have irritated plicae.

You can strengthen your quadriceps by doing:

  • quadriceps sets (muscle tightening)
  • straight leg raises
  • leg presses
  • mini-squats

You can also try swimming, biking, walking, or using an elliptical machine.

Hamstring stretching

The hamstrings are the group of muscles that stretch down the back of your thighs from your pelvis to your shin bone. You use them to bend your knee. Tight hamstrings place extra stress on the front of your knee, where your plica is.

A physical therapist can guide you through several stretches that can help relax your hamstrings. Most of them can be done while either sitting down or standing up. Once you learn some stretches, try to do them several times a day to keep your muscles relaxed.

Corticosteroid injections

Your doctor may give you a corticosteroid injection in your knee if the inflammation makes it hard to exercise. This may make the pain completely disappear, but it’s important to keep up with your stretching and exercise routine. If you don’t, the pain will return once the corticosteroid wears off.

If physical therapy doesn’t help, you may need a procedure called arthroscopic resection.

Your doctor will insert a small camera called an arthroscope through a small cut in the side of your knee. They’ll use small surgical tools, inserted through another small cut, to remove the plica or adjust its position.

After surgery, your doctor will refer you to a physical therapy program to help you rebuild your knee strength. You’ll start with gentle exercise to ease the pain and swelling. Eventually you’ll move on to more challenging exercises to strengthen your quadriceps, hamstrings, and calf muscles.

Recovering from surgery for plica syndrome depends on several factors, including your overall health and the affected knee. If you had surgery on your right knee, for example, you may need to wait about two weeks before driving. If your left knee was affected, you may fully recover within three to four days.

Keep in mind that you may need to wait several weeks before returning to your regular levels of exercise and physical activity.

Plica syndrome is usually easy to treat and manage with physical therapy and home exercises. If you do need surgery, the process is minimally invasive and requires less recovery than many other types of knee surgery.

Work with your doctor to figure out the right treatment option for you.