yogabook / pathology / synovial cyst

Definition

Synovial cysts in the strict sense are only pseudocysts lined with synovial epithelium of unclear aetiology in joint capsules, tendons or burses. Their wall contains granulation tissue, giant cells and histiocytes. The serous fluid inside is clear or only slightly coloured and contains many mucopolysaccharides (polysaccharides/glucosamine glycans). Synovial cysts do not necessarily have a connection to the joint cavity. They are intracapsular.

In contrast, ganglion cysts are filled with mucin, also do not necessarily have a direct connection to the joint space and often contain air, blood or haemosiderin. It cannot be ruled out that they develop from synovial cysts. As the two are very similar radiologically, clinically and in terms of handling, the terms are often used synonymously.
70% of synovial cysts occur between the 25th and 40th year of life, more frequently in women than in men. The most common synovial cysts are those of the dorsal wrist, then the palmar side of the wrist. Paralabral synovial cysts also occur at the shoulder joint and hip joint. They are also common in the facet joints of the spine. Spinal synovial cysts are extradural hernias of the joint capsule and are suspected in 1-10% of the population. The main localisations are L4-L5 and C5-C6 as well as C7-Th1. They increase with the age-related changes in the spine. In 50% of cases, these are incidental findings, otherwise they are associated with radiculopathies. Depending on their location and size, they can also lead to spinal canal stenosis and back pain through to cauda equina syndrome.
A distinction is made according to localisation:

• juxtaarticular: intraosseous (subchondral and without synovial lining) or in the soft tissues
• periosteal
• intra-articular, then mostly extrasynovial-intracapsular. In the knee joint, they are located in one of the cruciate ligaments or in the Hoffa’s fat body. They are also found in the long biceps tendon in the shoulder.
• Intramuscular

Synovial cysts are usually painless and in palpation are prallelastic. They usually develop within a few weeks and can often be reduced in size or made to disappear by pressure, but often recur. Conservative measures of the joint such as immobilisation, anti-inflammatory drugs or puncture can also cause them to disappear, also with a tendency to recur. If they restrict the function of the joint or press on a nerve, they must be removed invasively; if they are under the skin, a local anaesthetic is sufficient.

Cause

1. Overuse of the joint, which leads to the proliferation of mesenchyme, degeneration of connective tissue or overproduction of hyaluronic acid.
2. Degenerative or inflammatory processes (arthritis)

Predisposing

Diagnosis

1. Clinical
2. Sono, MRT

Symptoms

1. Symptom-free depending on size and location
2. possibly pressure pain with unfavourable joint position
3. Radiculopathies, if applicable

Therapy

1. Conservative treatment usually fails for spinal synovial cysts, therefore percutaneous cystectomy

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