The bursa synovialis is a connective tissue sac found in many parts of the body that is filled with synovium (synovial fluid). Its purpose is to act as a protective buffer between hard bones and soft tissues such as ligaments, tendons or skin. The most common clinical picture is bursitis, which usually results from overuse and presents with the classic signs of inflammation such as pain, swelling, hyperthermia and redness.
What are bursae?
In medical terminology, the bursa is called the bursa synovialis. The Latin word “bursa” (translated: pocket, pouch) refers to the appearance of the bursa in the form of a small sac that is flat when healthy. This is filled with synovial fluid, colloquially known as synovial fluid. Bursae are found in the body wherever the body’s support and movement system is exposed to particular mechanical stresses. Typical sites for bursae are the joints of the knee, elbow and shoulder, the space between the bone of the heel and the Achilles tendon, and on the thigh between the large rolling mound, a bony prominence, and the middle gluteal muscle. In terms of when they occur, bursae are divided into two categories: Congenital bursae are common to all people, while acquired forms first appear during life, usually in response to particular stresses.
Anatomy and structure
The structure of a bursa is very similar to that of the joint capsule. The outer covering is formed by a connective tissue layer called the stratum fibrosum. Inside, the bursa is lined with the so-called synovial layer, the stratum synovialis. The inner layer is so named because it is capable of secreting the fluid known as synovia, with which the connective tissue sac is filled. Bursae are found in numerous places in the human body and basically act as a protective buffer between bony elements and soft structures. With regard to the anatomical structures that the bursa separates, three types are distinguished: Cutaneous bursae (bursa subcutanea) are located under the skin – specifically, in areas of the body where the skin would otherwise directly meet a bony substrate. This type of bursa often has a reactive cause of formation. That is, they form only as a result of certain stresses. In contrast, tendon and ligament bursae (bursa subtendinea and subligamentosa, respectively) are generally congenital and act as the body’s own buffer between the delicate structures of the tendons and ligaments and the underlying hard bone structures.
Function and Tasks
The many bursae in the human body have a central function in protecting the musculoskeletal system from permanent or unilateral loads. The anatomical proximity of bones and softer structures such as ligaments, tendons or even the skin mean that constant contact can lead to painful irritation or even damage. An example of one of these buffers is the bursa subtendinea praepatellaris, which lies directly in the space between the kneecap and the tendon of the largest thigh muscle and thus prevents unfavorable friction at this movement-intensive location. The bursae protect the soft tissues from wear and tear on the bony structures in two ways at once: first, by their mere presence as a buffering shield, and second, by releasing synovial fluid to the outside of the joint, which causes the injury-prone tendon and ligament structures to move more easily and safely.
Diseases and ailments
By far the most common clinical picture in the area of the bursa is its inflammation (bursitis). It usually arises during permanent stress, often triggered by sports or one-sided occupational movements. Less frequently, injuries, infections, metabolic diseases such as gout or autoimmune diseases such as rheumatism also trigger bursitis. Typical of bursitis is a bulging connective tissue sac filled with fluid, which has a distinctly flat appearance when healthy. The result is pain accompanied by classic signs of inflammation such as hyperthermia, redness and swelling.Those affected usually have the feeling that they can no longer move the joint properly and not infrequently also express pressure pain. The physician can usually make the diagnosis by describing the symptoms, the typical localization of the event and a brief physical inspection. A distinction must be made between the acute and chronic course of bursitis: while the acute variant of bursitis is characterized by acute symptoms and clearly restricts the patient’s ability to move, the symptoms of the chronic form recur from time to time. Other symptoms related to the bursa result, for example, from trauma caused by falls or similar factors in sports. The consequences can be tears or bursting of the bursa.
