Plica of the Knee: What is it and how do you treat it?

Plica! I am sure you have heard of them, but do you know the likelihood of one of these patients showing up at your clinic door? Should you consider any special treatment recommendations with this population? Keep reading to find out!

Plica are inward folds of the synovial lining of the knee. Because they are embryonic deviations, plica are seen inconsistently throughout the population. Typically, they do not cause any pain and are asymptomatic, but they can become inflamed resulting in a "plica syndrome." From a clinical standpoint, it is important to note that "symptoms...are indistinguishable from other intra-articular conditions such as meniscal tears, articular cartilage injuries, or osteochondritic lesions, creating a diagnostic conundrum." 

There are 4 general categories of plica: suprapatellar, medial parapatellar, lateral, and infrapatellar. Lateral plica are very rarely seen and consequently little research has been conducted on them. Classification of each other type of plica becomes confusing because each one has multiple sub-groups. It is important to know that the suprapatellar plica does have attachments to the quadriceps tendon and depending on the size and shape, may create impingement between the patellar tendon and femoral trochlea in the range of 70-100 degrees of knee flexion. Similarly, the medial patellar plica also changes orientation with different positions of the knee. Its origin and attachment is controversial with several authors listing different anatomic variations. Finally, the infrapatellar plica is the most common plica in the population with 85% of patients presenting with one according to a study by Wachter in 1979. It runs superior-inferior from the intercondylar notch into the infrapatellar fat pad. The incidence of individuals with plica syndrome is under controversy, and some surgeons believe it is over-diagnosed. 

Clinically, 50% of patient's with plica syndrome will have a history of trauma or twisting at the knee joint. Once the initial injury is resolved, a patient maybe asymptomatic for a period of time, only to report back to the clinic weeks or months later with intense anterior knee pain. Anterior knee pain is known as the cardinal symtpom regardless of which plica is affected. Additionally, they may have complaints of a clicking or popping in the knee with flexion and describe the pain as intermittent, dull, and achy. Others report a tightness around the anterior medial knee joint which increases with deeper knee flexion angles. Because the incidence of plica syndrome is low, diligent differential diagnosis is a must, ruling out other possible causes of anterior knee pain. A clinical diagnosis alone is very difficult. Recent studies have shown the both MRI and Ultrasound have had good success in viewing plica shape and size.

So what can we do for these patients? Unfortunately, "success rates of conservative management are generally low" with age being a predictive factor for your success. The younger patient is more likely to respond favorably to conservative treatment since they have not suffered the long-term effects of impinging plica and resulting structural changes within the knee joint. Therapy should consist of a period of rest from deep knee flexion activites, followed by a course of NSAIDs to help curb inflammation. Caution should be taken with intense exercise progression secondary to likelihood of aggravating the plica. Additionally, success rates of PT alone are variable and surgical intervention may be required with persistent symptoms. It should be noted that while this is a recent article, many of the references under conservative management are fairly dated. The therapy profession has since grown in its knowledge of conservative treatment for knee conditions and the importance of regional interdependence around the knee joint. 

In conclusion, plica syndome is not something you will see in the clinic everyday, but having this knowledge in your toolbox will make you a more well-rounded clinician. Reading this article would be very beneficial because there are great pictures discussing different variations and anatomic location.

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References: 
Schindler O. 2013. 'The Sneaky Plica' revisited: morphology, pathophysiology, and treatment of synovial plicae of the knee. Knee Surg Sports Traumatol Arthrosc. 2013; 2013. Web. 14 May 2013.