The Plica: Is a New Aetiological Factor in the Knee Osteoarthritis?

Abstract

Osteoarthritis is one of the most important diseases in the field of orthopedics worldwide. The disease is characterized by progressive loss of articular cartilage and formation of osteophytes, which lead to chronic pain and functional restrictions in the affected joints. Different factors can be involved in the development of osteoarthritis including traumatic events, genetic predisposition, defective position of joints, and ageing and malnutrition. The plica is the generic name of the ruins or folds of the synovial membrane in the knee joint. The incidence of the plicas in the knee joint is between 18,5-87 %. These plicas are named and classified according to their settlements in the knee joint (1-6). The plicas sometimes come to a pathologic state, which gains clinical importance and causes the plica syndrome (7). When plica is symptomatic, the condition is called plica syndrome. The plicas are considered to be one of the potential causes of the complaints around the knee joint (8). It is known that medial plica causes to degeneration of cartilage around the medial femoral condyle of the knee joint and / or the medial pole of the patella (2,8-14). Owing to the anatomic location of the medial plica, a loss of normal elasticity can cause it to impinge on the femoral medial condyle or the medial facet of the patella during flexion–extension motion of the knee. This kind of repetitive contact may result in a chondral lesion of varying severity, sometimes referred to as an impingement lesion (2,7,8,14-18). It has also been suggested that normal-looking medial plica, not impinging on the articular surfaces, could be symptomatic as well . This is supported by recent findings which have demonstrated an increase in the amount of nerve endings in the plica after trauma or overuse, indicating increased pain sensitivity and sensation of pain (19,20). The anatomy of the plicas or synovial folds was first described by Mayeda in 1918. In 1939, Lino first described the appearance of arthroscopic synovial folds in the cadaveric knees. In 1950 and 1971, Pipkin reported that the plicas should be distinguished from adhesions in the knee joint and those might cause clinical symptoms (21,22).