In addition to the bone, cartilage, synovium and capsule, there are other structures within the joint. They include the menisci. These structures are made of fibrocartilage and when looked down upon (in plan view), have a “C” shape. When they are looked on in end elevation, they have a wedge shape. The peripheral parts of the menisci are thick and the parts nearer the centre of the joint (both medially and laterally) are quite thin.
The menisci are sometimes referred to as the “cartilage”. You may recall friends of yours sustaining a “cartilage tear” many years ago whilst playing football and undergoing an operative removal of the “cartilage”. It would have been the meniscus that they were talking about.
Meniscal tears are usually of a traumatic origin. Occasionally, tears can occur through a degenerate region in the process of osteoarthritis.
Some meniscal tears are of no great significance. Others can give rise to considerable pain and impingement between the lower end of the thigh bone and the upper end of the shin bone (the two bones that form the knee joint).
The tears can be so large on occasions that they will actually jam the joint. This is so-called “locking”. It typically occurs when the knee joint is flexed (say at about 90°) and the patient is unable to extend beyond that position. Then the joint will suddenly “unlock” with a click or a clunk and a sudden sharp pain. The joint can then move relatively normally until it locks again. It is this recurrent locking that assists the Orthopaedic Surgeon greatly in making the diagnosis of a significant meniscal tear.
Some meniscal tears can be left alone. Others do require partial or complete resection. Whereas 30 years ago the joint was opened such that the meniscal tear could be addressed, this type of surgery is now performed arthroscopically by Orthopaedic Surgeons around the world. This has dramatically reduced the morbidity associated with the procedure, shortened the hospitalisation time from several days to just a few hours, and greatly improved the post-operative rehabilitation progress experienced by the patient.