Knee plica refers to a common, normal fold of tissue found within the knee joint. These folds are remnants from the knee’s development before birth, typically going unnoticed throughout a person’s life. While generally harmless and often asymptomatic, understanding these structures is important for recognizing when they might become a source of discomfort. This article explores the nature of knee plica, what causes them to become problematic, how they are identified, and the available treatment options.
Understanding Knee Plica
Plicae are folds in the synovial membrane, a thin tissue lining the knee joint capsule that helps lubricate the joint. During embryonic development, the knee joint is divided into compartments by these membranes, which usually resorb, or fold inward, by 8-12 weeks of fetal growth to form a single knee cavity. However, in many individuals, this resorption is not complete, leaving behind these folds of synovial tissue. Plicae are estimated to be present in about 50% of the population.
There are typically four types of plicae found in the knee based on their anatomical location: suprapatellar, infrapatellar, medial patellar, and lateral patellar. The medial patellar plica, located on the inner side of the knee joint, is the most frequently symptomatic among them, despite being less common than suprapatellar or infrapatellar plicae. When healthy, these elastic folds allow for normal knee movement without restriction.
When Plica Becomes a Problem
A plica causes problems when it becomes irritated or inflamed, leading to a condition known as plica syndrome. This irritation can stem from various factors, including repetitive knee motion, direct trauma, or overuse. Activities that involve repeated bending and straightening of the knee, such as running, cycling, or using a stair machine, can stress the plica and cause inflammation. A direct impact to the knee, like a fall or a car accident, can also injure the plica and the surrounding synovial tissue, causing it to swell and become painful.
Once inflamed, the plica can thicken and become less elastic, potentially leading to scarring over time. This thickened plica may then catch or rub against the thighbone, resulting in symptoms. Common symptoms include pain, often on the inner side of the knee or around the front. Individuals might also experience a clicking, popping, or snapping sensation when bending or straightening the knee, a feeling of catching or locking, and sometimes localized swelling or tenderness. Pain can worsen with activities like squatting, climbing stairs, or prolonged sitting.
Diagnosing Plica Syndrome
Medical professionals diagnose plica syndrome through a comprehensive evaluation that begins with a detailed patient history and a physical examination. During the physical exam, a healthcare provider may palpate the knee to feel for a tender, cord-like band, particularly over the medial patellar plica. Specific maneuvers, such as provocative tests, may be performed to reproduce symptoms and identify the irritated plica.
Imaging studies like X-rays are usually normal in cases of plica syndrome and are primarily used to rule out other knee conditions. Magnetic Resonance Imaging (MRI) can visualize plicae and detect thickening or inflammation, especially if there is fluid within the joint. However, MRI is often more useful for excluding other potential causes of knee pain, such as meniscus tears, ligament injuries, or cartilage defects. Plicae are normal anatomical structures and may not appear abnormal on imaging even when symptomatic, so MRI is less definitive for diagnosis. The diagnosis relies heavily on clinical findings and the exclusion of other pathologies.
Managing Plica Syndrome
Managing plica syndrome typically begins with conservative treatments, which are effective for most individuals. Initial approaches include rest and avoiding activities that aggravate symptoms, such as deep squats or repetitive knee bending. Applying ice to the affected area helps reduce pain and inflammation. Over-the-counter non-steroidal anti-inflammatory drugs (NSAIDs) can also alleviate discomfort and swelling.
Physical therapy plays an important role in rehabilitation, focusing on strengthening the quadriceps muscles and stretching the hamstrings to improve knee mechanics and reduce tension on the plica. Strengthening exercises for the quadriceps, such as straight leg raises and mini-squats, are often incorporated. If conservative measures do not provide sufficient relief, corticosteroid injections may be considered to reduce inflammation.
For persistent cases that do not respond to conservative management, surgical intervention, specifically arthroscopic plica excision, may be recommended. This minimally invasive procedure involves removing the irritated plica. Arthroscopic excision has a high success rate. Recovery from surgery usually involves a period of rehabilitation and can take several weeks to months depending on the severity.