Plica Syndrome

What is Plica Syndrome?

In simple terms, a plica is a band of thick tissue that expands from the protective cover of a joint. While a plica can exist in several joints, this discussion focuses on the knee, which is the joint most commonly affected by it. Overuse or injury can cause the plica to swell or get irritated because of rubbing against the kneecap or the inner part of the thighbone.

When the plica becomes inflamed or irritated, it can lead to what’s known as plica syndrome, which causes pain at the front of the knee due to the irritated plica.

What Causes Plica Syndrome?

There’s some disagreement among healthcare professionals about how the knee joint develops in a fetus. One common theory is that the important structures in the knee, like the menisci (pieces of cartilage that cushion the joint), cruciate ligaments (bands of tissue that connect bones), and a joint cavity (space where bones meet) are all formed when the fetus is 8 weeks old.

Over the following 2 weeks, the septa (a separating wall) of the synovium (the thin layer of tissue lining the joints) are absorbed, and a larger cavity forms. This eventually becomes the knee joint. Sometimes, this larger cavity might not fully join together. When this happens, a type of tissue called mesenchymal tissue can create folds in the synovium. These folds are known as plicae, which are folds of synovial membrane in the knee.

Risk Factors and Frequency for Plica Syndrome

Plica syndrome, a condition that can cause knee pain, is not thoroughly understood. The number of reported cases varies greatly in medical literature with most studies suggesting that about 10% of people have it based on arthroscopic (a procedure allowing doctors to look at the inside of a joint) investigations. A common belief is that plica syndrome is often not diagnosed correctly, as its symptoms resemble those associated with other causes of knee pain.

• In one study in Japan, they examined 3,889 knee joints with arthroscopy and discovered a high incidence of medial plica, a specific type of plica in the knee, in 79.9% of cases.
• However, this study didn’t claim that the medial plica was the root of symptoms in all these patients. Therefore, these figures represent the incidence of medial plica, not necessarily plica syndrome.
• Further reviews of the literature showed that plica are physically present in around half of all individuals based on post-mortem examinations.

As a result, the presence of plica detected during arthroscopy doesn’t necessarily mean that these will result in clinical plica syndrome or plica-related symptoms in all individuals.

Signs and Symptoms of Plica Syndrome

Plica syndrome is a condition that causes pain in the front of the knee, often along with a clicking or popping sound. This knee pain can become worse when standing up from a chair, squatting, going up or down stairs, or doing anything else that puts pressure on the knee joint. Sometimes, the patient might have had an injury or a twist to the knee, but in other cases, there might not be any obvious cause. There can also be other issues contributing to plica syndrome, like bleeding in the joints due to hemophilia, lesions within the joint, loose foreign bodies, or rheumatoid arthritis.

During a physical examination, a doctor might be able to feel a tight band under the skin, which could be tender when touched. If this band is present, the doctor will check the other knee to see if the same band can be felt there. Other things the doctor might find during the examination include fluid around the joint, tight hamstrings (muscles at the back of the thigh), and tight quadriceps (muscles at the front of the thigh).

There are also two specific tests that can be done to help diagnose plica syndrome. These are called the Stutter test and the Hughston test.

• In the Stutter test, the patient sits upright with the legs hanging freely off the edge of the table, bent at a 90-degree angle. The doctor then places their index and middle fingers on the center of the kneecap of the affected leg. As the patient extends the leg, the doctor feels for a stuttering movement of the kneecap, which is a positive result.
• In the Hughston test, the patient lies flat with the knee straight. The doctor stands at the side of the affected knee and positions their hands around the patient’s heel and on top of their kneecap. The doctor then pushes the kneecap towards the inside and rotates the shin while moving the patient’s knee through bending and straightening. If the patient feels pain or the doctor can feel a popping sound during these movements, this test is also positive.

A positive result from both tests suggests plica syndrome, but if only one test is positive, plica syndrome should still be considered as a possible diagnosis.

Testing for Plica Syndrome

If your doctor suspects that you have plica syndrome, they might take different types of X-rays. These include anteroposterior (front-to-back), lateral (side), and skyline (view from above) X-rays. Even so, these X-rays can sometimes look normal, even if you do have plica syndrome.

Magnetic resonance imaging (MRI), which is a type of scan that uses powerful magnets and radio waves to create pictures of the inside of your body, can also be useful. Whether or not an MRI is helpful in diagnosing plica syndrome is a topic of debate among medical professionals.

Plica (folds or ridges in the lining of the knee joint) are occasionally visible on MRI, and they can be seen more easily if there is an excess of fluid in the joint. If your doctor can see plica on the MRI, they usually appear as a low-signal intensity, or darker areas on the scan. They might also be able to tell whether the plica are causing symptoms by looking at their thickness and signs of inflammation. Plica causing symptoms can appear thicker and inflamed, compared to normal plica which may appear thinner.

Because of these characteristics, an MRI scan can be useful in planning surgery and is also important to look for other potential causes of knee pain.

According to a literature review that examined multiple studies focusing on 492 knees, physical exams were found to have a 90% sensitivity (accuracy in identifying the disease) and 89% specificity (accuracy in identifying those without the disease), while ultrasounds had 90% sensitivity and 83% specificity. Conversely, MRIs showed 77% sensitivity and 58% specificity. The gold standard, or most reliable test for diagnosis, is arthroscopy, which is a type of keyhole surgery where a camera is inserted into the knee to look for any abnormalities.

Treatment Options for Plica Syndrome

Plica syndrome, a condition where the folds in the knee become irritated or inflamed, can be treated in several ways. Your treatment will depend on the classification of your plica syndrome, which is split into categories ‘A’ through ‘D’ according to the Sakakibara classification system. Types ‘A’ and ‘B’ are smaller and less likely to cause pain, so these are usually managed with conservative treatments. In contrast, types ‘C’ and ‘D’ are larger and can press against the bony prominence on the side of the knee (medial condyle), often causing more discomfort.

The first step in treating plica syndrome usually involves stretching and strengthening exercises, either at home or with a physical therapist. The aim here is to make the muscles and connective tissues around the knee stronger, including the quadriceps, hamstrings, and joint capsule musculature. Over-the-counter anti-inflammatory drugs and ice can help reduce inflammation, and avoiding activities that cause pain can also help. This conservative treatment is recommended for at least three months. One study, for instance, found that most patients using these methods returned to normal function without their symptoms recurring. Some people noticed occasional symptoms, but these were manageable.

If these strengthening and stretching exercises don’t alleviate your symptoms, corticosteroid injections into the irritated knee folds (intraplical injections) might be an option. This can particularly help if you’re in the early stages of the disease and conservative treatment hasn’t provided relief. A study of 31 patients with medial plica syndrome (irritation of the fold on the inner side of the knee) found that 73% of those treated with steroid injections returned to their normal activities with complete pain relief.

In cases where conservative management or intraplical steroid injections don’t work, another option is arthroscopic resection. In this procedure, a small camera (arthroscope) is inserted into the knee to guide the surgeon in removing the irritated knee fold. This approach is often used for ‘C’ and ‘D’ type folds and when there’s potential cartilage damage. One study found that, compared to conservative management, arthroscopy had a better and more long-lasting therapeutic effect in treating plica syndrome.

What else can Plica Syndrome be?

Symptoms of plica syndrome can often resemble symptoms of several other knee conditions, making an accurate diagnosis a bit tricky. Conditions that mimic plica syndrome could be:

• Osteochondritis dissecans
• Patellofemoral syndrome
• Patellofemoral subluxation
• Meniscal disease
• Osteoarthritis
• Patellar tendonitis
• Cruciate ligament problems
• Pigmented villonodular synovitis

However, each of these conditions can be distinguished from plica syndrome in the following ways:

• Osteochondritis dissecans can be confirmed using x-rays or MRI scans.
• Patellofemoral syndrome often shares symptoms with plica syndrome, making it difficult to differentiate the two. However, other causes of patellofemoral pain, like chondromalacia, may be revealed through medical history and imaging.
• People with patellofemoral subluxation usually recount past experiences of knee dislocation and often show apprehension when the knee is displaced sideways.
• Meniscus problems usually are accompanied by pain at the joint line, whereas plica syndrome pain is often above the joint line. Certain physical exams can help distinguish between the two.
• Osteoarthritis can be confirmed through x-rays that reveal reduced joint space, growths of bony spikes around the joint edges (osteophytes), hardening of a section of bone underneath a damaged joint cartilage (subchondral sclerosis), fluid-filled sacs in a joint (subchondral cysts), among others. However, this doesn’t entirely rule out plica syndrome.
• Patellar tendonitis can be differentiated by touching and feeling the patellar tendon at its connection points.
• Cruciate ligament problems can be discovered with physical exams that test for looseness in the knee.
• Pigmented villonodular synovitis (PVNS) can be identified via MRI scans.

What to expect with Plica Syndrome

Plica syndrome generally has a positive outcome once it has been treated properly. In one study consisting of 969 patients, it was observed that around 10% didn’t show a response to the treatment after an average of 27.5 months. However, 26% of patients showed improvement and the majority, about 64%, were free from any symptoms.

Possible Complications When Diagnosed with Plica Syndrome

Research shows that the friction between a part of the knee called the medial plica and the medial femoral condyle, another part of the knee, might result in damage to the cartilage, which is the tissue protecting the knee joint. This was supported by another study involving 48 patients. These patients underwent knee replacement surgery due to severe osteoarthritis in the inner part of the knee, and all of them had a medial plica and a damaged cartilage spot on their medial femoral condyle touching the plica.

Medial plica syndrome can be serious if it is not addressed. In its final stages, it can cause what are known as grade IV Outerbridge chondral lesions, in which the bone underneath the cartilage becomes visible. These types of lesions are challenging to treat – highlighting the need for early diagnosis and treatment of plica syndrome to prevent these serious issues.

Key Points:

• The friction between the medial plica and the medial femoral – part of the knee can cause damage to the cartilage.
• Studies show that patients with medial plica syndrome have damaged cartilage spots on their knee that are in contact with the plica.
• If left untreated, medial plica syndrome can lead to grade IV Outerbridge chondral lesions where the underlying bone becomes visible.
• These lesions are tough to treat – emphasizing the need for early diagnosis and treatment of plica syndrome.

Preventing Plica Syndrome

It’s important for patients to understand that if their condition is treated quickly and correctly, the outlook is usually good. If you’ve been given a home exercise plan, stick to it, as it’s an essential part of the non-surgical treatment for plica syndrome, a condition where the tissue in the knee becomes irritated or inflamed. If you’re experiencing ongoing knee pain, it’s crucial to get treatment to find out the cause and start treatment before it gets worse, such as progressing to grade IV Outerbridge lesions – a severe level of cartilage damage in the knee. Once the condition has progressed to this stage, treating it becomes much harder.