Aponeuroses are usually flat tendon plates made of connective tissue that serve the tendinous attachment of muscles. In addition to the hand, foot, and kneecap, the abdomen, palate, and tongue have aponeuroses. The most common disease of the tendon plates is inflammation, which is called fasciitis.
What is an aponeurosis?
The medical term aponeurosis comes from Latin. Literally translated, the term means tendon plate. This refers to the flat or platy connective tissue structures that serve the tendinous attachment of one or more muscles and appear as extensions of muscle end tendons. Well-known examples of aponeuroses include the palmar aponeurosis, the plantar aponeurosis, the rectus sheath, the lingual aponeurosis, and the retinaculum patellae. The plantar aponeurosis braces and maintains the arch of the foot. It thus protects the muscles, nerves, blood vessels and tendons on the sole of the foot. The palmar aponeurosis on the hand has similar functions. The structure of the aponeuroses differs with the localization. The aponeurosis differs from other types of connective tissue mainly in its function and its anatomically layered form. All aponeuroses are always directly related to at least one muscle and its tendon.
Anatomy and structure
The palatal aponeurosis is highly fibrous layer of connective tissue that serves as the base of the soft palate. Palatal muscles for palatal movement radiate into the connective tissue. Palmar aponeurosis consists of complex three-dimensional longitudinal, transverse and vertical fibers and is connected to the surface fascia of the hand by fibrous connective tissue. It lies in the central palm on the short palm muscles and fuses laterally with the fascia of the hypothenar and thenar muscles. The plantar aponeurosis roots at the calcaneus and diverges in a V-shape into metatarsophalangeal joint capsules and toe flexor tendons of the metatarsophalangeal joint. The rectus sheath consists of the aponeuroses of the three abdominal wall muscles, musculus obliquus internus abdominis, musculus transversus abdominis, and musculus obliquus externus abdominis. It encases the rectus abdominis muscle. The lingual aponeuros is a layer of coarse connective tissue between the lingual mucosa and the lingual musculature. The aponeurosis retinaculum patellae is supportive of the patella and is part of the outer joint capsular layer of the knee joint.
Function and tasks
The main function of all aponeuroses is to form the muscle tendon insertion. In this context, the palatal aponeurosis is often referred to as a functional tendon extension of the musculi tensor veli palatini. However, current evidence suggests that this aponeurosis is more likely an extension of adjacent bony periosteum. The palmar aponeurosis is irreplaceable for the grasping movement of the hand. It tightens the skin on the palmar side of the hand. Because of its fibrous tracts, it establishes close contact between the grasped object and the hand and at the same time protects the blood vessels and nerves under the connective tissue layer. The plantar aponeurosis stabilizes the longitudinal arch of the foot skeleton. It has an ideally functional lever arm for arch bracing. Through dense fiber bundles, the aponeurosis is fused into the plantar fascia and fixes the skin through this tight anchorage. In this way, it creates the basis for secure footing. The fat cushions between its fibrous tracts serve as pressure pads. The rectus sheath shortens the muscle fibers of the abdominal wall. If the abdominal wall contracted too tightly, the abdominal cavity would be constricted and the organs would not have enough room. The rectus sheath also joins the tendon plates of the abdominal muscles into a single unit. The lingual aponeurosis serves the stable attachment of the tongue muscles and the retinaculum patellae forms a retaining ligament for the kneecap. Common to all aponeuroses is therefore a stabilizing and holding function. In most cases, the connective tissue layers also assume protective functions. Despite these tasks, the structures are rather passive structural elements.
Diseases
Any aponeurosis of the body can be affected by inflammation. This pathologic phenomenon is also known as fasciitis and most commonly affects the plantar aponeurosis of the foot. When the plantar tendon plate is inflamed, the doctor speaks of plantar fasciitis. In most cases, this phenomenon is preceded by overuse of the associated musculature.Such overloads occur mainly during sports, jumping or running. Dancing, soccer and basketball are considered risk factors. In addition to overloads, the inflammations can also be caused by previous injuries to the foot. Plantar fasciitis manifests itself in severe pain in the area of the heel, which usually increases with stress. The onset is insidious. As it progresses, the symptoms intensify over weeks or even months. The pain may cause inability to walk at the climax of the disease. Usually, the pain shoots in sharply at the beginning of an exertion, but fades away within a certain duration of exertion. The foot aponeuroses are also affected by Ledderhose’s disease, which causes thickening of the connective tissue and corresponds to fibromatosis. In the hand aponeurosis, the same phenomenon is called Dupuytren’s disease. In both phenomena, nodules form in the aponeuroses and slowly increase in size. Painful nodules can limit the ability to move. Therefore, although both conditions are considered benign, surgical removal may be indicated. The primary cause of the growths is as yet unknown. The myofibroblasts cause the connective tissue proliferation. What factors stimulate them to do so is the subject of current research. Speculation suggests that injury, genetic components, primary diseases such as diabetes mellitus, and nicotine or alcohol consumption may play a role in the etiology of the disease. All patients with a benign connective tissue proliferation at a specific body site are at increased risk of developing further connective tissue proliferations.
