Medial Plica Syndrome (MPS) is a common cause of pain felt in the front part of the knee, often mistaken for other conditions. This disorder involves the irritation of a specific tissue fold, the medial plica, located on the inner side of the kneecap. The discomfort can significantly affect daily activities and exercise, particularly those involving repetitive knee movement.
Understanding the Medial Plica
The medial plica is a remnant of embryonic tissue, remaining as a fold in the synovial membrane, the lining of the knee joint. In the developing knee, three compartments merge to form a single joint cavity, leaving the plica as a soft, shelf-like band of tissue. The medial plica is the most common of these folds to become symptomatic, sitting on the inner side of the knee joint.
This structure becomes problematic when it loses elasticity and thickens, often due to injury or overuse. The thickened plica rubs repeatedly against the lower end of the thigh bone (femoral condyle) during knee movement. This friction causes inflammation (synovitis), leading to pain and irritation within the joint. Activities involving repetitive knee flexion and extension, such as running or cycling, commonly cause this irritation, as can direct trauma to the knee.
Symptoms and Diagnosis
Symptoms are localized, often presenting as aching pain over the anteromedial aspect of the knee (the inner side near the kneecap). This discomfort increases with activity, especially when climbing stairs, squatting, or sitting for long periods, known as the “movie theater sign.” A palpable, tender cord of tissue may be felt along the medial edge of the kneecap during examination.
Many individuals experience mechanical symptoms, such as clicking, popping, or snapping when the knee moves. Patients may also describe the knee “giving way” or a momentary locking sensation (pseudo-locking). Diagnosis relies on a thorough clinical examination and patient history. During the physical exam, a physician may use specific provocative tests, like the Plica Stutter Test, to reproduce the clicking or pain.
Imaging studies, such as X-rays or MRI, are used primarily to exclude other knee pathologies. Conditions like a meniscus tear, patellofemoral pain syndrome, or cartilage damage can mimic plica symptoms and must be ruled out. Although an MRI can sometimes show a thickened plica, the diagnosis is confirmed when clinical symptoms align with physical findings and other conditions are eliminated. The presence of a plica alone does not confirm the syndrome, as many people have asymptomatic folds.
Treatment and Rehabilitation
Management is divided into non-surgical and surgical phases, though the majority of cases respond well to conservative treatment. The initial approach focuses on reducing inflammation and modifying aggravating activities. This includes resting the joint from high-impact activities and using Nonsteroidal Anti-Inflammatory Drugs (NSAIDs) to manage pain and swelling. If inflammation persists, a corticosteroid injection may be administered directly into the plica area for temporary relief.
Physical therapy is the primary non-operative treatment, aiming to address underlying biomechanical factors. Rehabilitation programs focus on strengthening the quadriceps muscles, which stabilizes the kneecap and reduces friction on the plica. Stretching the hamstring muscles and hip flexors is also important, as tightness in these areas increases stress on the anterior knee joint. A consistent program of stretching and strengthening often leads to significant symptom improvement within several weeks.
If conservative management, including physical therapy, fails to resolve symptoms after six to twelve weeks, surgical intervention may be considered. The procedure is an arthroscopic resection, where a surgeon uses small instruments inserted through tiny incisions to remove the irritated plica tissue. Recovery from this minimally invasive procedure is straightforward, with a return to full activities typically occurring within six to twelve weeks. Post-surgical rehabilitation focuses on regaining full range of motion and muscle strength.