Synovial osteochondromatosis

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Synovial osteochondromatosis
Synovial osteochondromatosis
Specialty Rheumatology   OOjs UI icon edit-ltr-progressive.svg

Synovial osteochondromatosis (SOC) (synonyms include synovial chondromatosis, primary synovial chondromatosis, synovial chondrometaplasia) is a rare disease that creates a benign change or proliferation in the synovium or joint-lining tissue, which changes to form bone-forming cartilage. In most occurrences, there is only one joint affected, either the knee, the hip, or the elbow. Rarely involves the TMJ. [1]


The cause is unknown.

In this condition, cartilaginous metaplasia takes place within the synovial membrane of the joint. Metaplastic synovium organizes into nodules. With minor trauma, nodules are shed as small bodies into the joint space. In some patients, the disease process may involve tendon sheaths and bursal sacs.

Cartilaginous intra-articular bodies float freely within the synovial fluid, which they require for nutrition and growth. Progressive enlargement and ossification occur with time. If they remain free, they continue to grow larger and more calcified. In severe cases, they may occupy the entire joint space or penetrate to adjacent tissues. Also, they can deposit in the synovial lining, reestablish a blood supply, and become replaced by bone. On occasion, synovial reattachment can lead to complete reabsorption of the cartilage fragment.

Signs and symptoms

Chronic, progressive pain and swelling of the affected joint are exacerbated by physical activity. Joint effusion and limited range of motion are common associated features. It affects primarily large joints, including knee (>50% of cases), elbow, hip, and shoulder. SOC is twice as common in men as women. Some patients have intra-articular bodies resting in stable positions within joint recesses or bursae. These patients may be asymptomatic, with SOC merely as an incidental finding at imaging.[ citation needed ]


Malignant transformation to synovial chondrosarcoma. This is a very rare complication occurring in chronic cases. Treatment entails synovial excision and total joint replacement.[ citation needed ]

Clicking, grating, or locking may result from acute mechanical problems due to intra-articular bodies within the affected joint. Locking may destroy articular cartilage, resulting in secondary osteoarthritis. Symptoms such as joint stiffness and aching are the result of osteoarthritis that sets in after years of persistent joint irritation. [2]



Typical finding is of multiple, smooth, oval-shaped calcified masses within the joint space or bursa. They have a characteristic popcorn-ball appearance of calcified cartilage. With serial imaging, masses may be found to change in size, disappear, or migrate to recessed areas of the joint. They may pass from the main joint cavity into a neighboring synovial cyst. For this reason, a mass may not be appreciated within the actual joint space itself.[ citation needed ]

Additional radiographic findings include joint effusion and degenerative changes such as joint space narrowing, subchondral sclerosis, and osteophyte formation.[ citation needed ]

Computed tomography

CT is best utilized in earlier stages of the disease process before cartilaginous bodies have calcified (become filled with calcium). CT can effectively detect non-calcified masses or those with only minimal calcification, which allows the radiologist to distinguish this condition from a simple joint effusion.[ citation needed ]

Magnetic resonance imaging

MR appearance depends on the composition of the intra-articular body. Entirely cartilaginous bodies will appear isointense to muscle on T1 and hyperintense to muscle on T2 weighted images. Partly calcified intra-articular bodies demonstrate foci of absent signal on all pulse sequences. Like CT arthrography, MR with gadolinium may be used to detect intra-articular bodies that have not yet calcified.[ citation needed ]


Cartilaginous bodies or osteocartilaginous bodies with central ossification may be noted. They are typically spherical in shape. Sizes range from several millimeters to several centimeters in diameter. The synovium of the involved joint demonstrates villous hyperplasia, which imparts a wrinkled appearance on gross examination. There may be cartilaginous bodies attached to the synovium. Synovial involvement may be focal or diffuse in nature. [3]

Differential diagnosis

Intra-articular bodies in SOC typically have popcorn calcification, with a dense sclerotic border with radiolucent central region. This distinct radiographic appearance sets it apart from other causes of intra-articular bodies. Number and size of intra-articular bodies can prove helpful as well. SOC typically presents as multiple intra-articular bodies. Few or isolated intra-articular bodies are more consistent with trauma or osteoarthritis.[ citation needed ]


Classification is divided into primary versus secondary SOC. Primary SOC occurs in an otherwise normal joint. It is suggested by monoarticular involvement in a patient in the third to fifth decades of life. Secondary SOC occurs in older patients in joints previously affected by joint disease such as osteoarthritis. This pattern is suggested by bilateral involvement with multiple joint intra-articular bodies.[ citation needed ]


Asymptomatic patients do not require therapy. Symptomatic patients should undergo arthroscopic or surgical removal of intra-articular bodies. Patients who have recurrent intra-articular bodies or in whom the entire synovial lining is metaplastic require total synovectomy.

Related Research Articles

Cartilage Resilient and smooth elastic tissue in animals

Cartilage is a resilient and smooth elastic tissue, rubber-like padding that covers and protects the ends of long bones at the joints and nerves, and is a structural component of the rib cage, the ear, the nose, the bronchial tubes, the intervertebral discs, and many other body components. It is not as hard and rigid as bone, but it is much stiffer and much less flexible than muscle. The matrix of cartilage is made up of glycosaminoglycans, proteoglycans, collagen fibers and, sometimes, elastin.

Joint Location at which two or more bones make contact

A joint or articulation is the connection made between bones in the body which link the skeletal system into a functional whole. They are constructed to allow for different degrees and types of movement. Some joints, such as the knee, elbow, and shoulder, are self-lubricating, almost frictionless, and are able to withstand compression and maintain heavy loads while still executing smooth and precise movements. Other joints such as sutures between the bones of the skull permit very little movement in order to protect the brain and the sense organs. The connection between a tooth and the jawbone is also called a joint, and is described as a fibrous joint known as a gomphosis. Joints are classified both structurally and functionally.

Synovial membrane

The synovial membrane is a specialized connective tissue that lines the inner surface of capsules of synovial joints and tendon sheath. It makes direct contact with the fibrous membrane on the outside surface and with the synovial fluid lubricant on the inside surface. In contact with the synovial fluid at the tissue surface are many rounded macrophage-like synovial cells and also type B cells, which are also known as fibroblast-like synoviocytes (FLS). Type A cells maintain the synovial fluid by removing wear-and-tear debris. As for the FLS, they produce hyaluronan, as well as other extracellular components in the synovial fluid.

Osteoarthritis Form of arthritis caused by degeneration of joints

Osteoarthritis (OA) is a type of degenerative joint disease that results from breakdown of joint cartilage and underlying bone. The most common symptoms are joint pain and stiffness. Usually the symptoms progress slowly over years. Initially they may occur only after exercise but can become constant over time. Other symptoms may include joint swelling, decreased range of motion, and, when the back is affected, weakness or numbness of the arms and legs. The most commonly involved joints are the two near the ends of the fingers and the joint at the base of the thumbs; the knee and hip joints; and the joints of the neck and lower back. Joints on one side of the body are often more affected than those on the other. The symptoms can interfere with work and normal daily activities. Unlike some other types of arthritis, only the joints, not internal organs, are affected.

Synovial joint

A synovial joint, also known as diarthrosis, joins bones or cartilage with a fibrous joint capsule that is continuous with the periosteum of the joined bones, constitutes the outer boundary of a synovial cavity, and surrounds the bones' articulating surfaces. This joint unites long bones and permits free bone movement and greater mobility. The synovial cavity/joint is filled with synovial fluid. The joint capsule is made up of an outer layer, the articular capsule, which keeps the bones together structurally, and an inner layer, the synovial membrane, which seals in the synovial fluid.

Synovial fluid Fluid found in the cavities of synovial joints

Synovial fluid, also called synovia,[help 1] is a viscous, non-Newtonian fluid found in the cavities of synovial joints. With its egg white–like consistency, the principal role of synovial fluid is to reduce friction between the articular cartilage of synovial joints during movement. Synovial fluid is a small component of the transcellular fluid component of extracellular fluid.

Enchondroma Medical condition

An enchondroma is a benign cartilage tumour found inside bones. Typically, enchondroma is discovered on an X-ray scan. Enchondromas have a characteristic appearance on Magnetic Resonance Imaging (MRI) as well. They have also been reported to cause increased uptake on PET examination.

Calcium pyrophosphate dihydrate crystal deposition disease Medical condition

Calcium pyrophosphate dihydrate (CPPD) crystal deposition disease, also known as pseudogout and pyrophosphate arthropathy, is a rheumatologic disease which is thought to be secondary to abnormal accumulation of calcium pyrophosphate dihydrate crystals within joint soft tissues. The knee joint is most commonly affected.

Osteochondroma Medical condition

Osteochondromas are the most common benign tumors of the bones. The tumors take the form of cartilage-capped bony projections or outgrowth on the surface of bones exostoses. It is characterized as a type of overgrowth that can occur in any bone where cartilage forms bone. Tumors most commonly affect long bones about the knee and in the forearm. Additionally, flat bones such as the pelvis and scapula may be affected. Hereditary multiple exostoses usually present during childhood. Yet, the vast majority of affected individuals become clinically manifest by the time they reach adolescence. Osteochondromas occur in 3% of the general population and represent 35% of all benign tumors and 8% of all bone tumors. The majority of these tumors are solitary non-hereditary lesions and approximately 15% of osteochondromas occur as hereditary multiple exostoses preferably known as hereditary multiple osteochondromas (HMOs). Osteochondromas do not result from injury and the exact cause remains unknown. Recent research has indicated that multiple osteochondromas is an autosomal dominant inherited disease. Germ line mutations in EXT1 and EXT2 genes located on chromosomes 8 and 11 have been associated with the cause of the disease. The treatment choice for osteochondroma is surgical removal of solitary lesion or partial excision of the outgrowth, when symptoms cause motion limitations or nerve and blood vessel impingements. In hereditary multiple exostoses the indications of surgery are based upon multiple factors that are taken collectively, namely: patient's age, tumor location and number, accompanying symptomatology, esthetic concerns, family history and underlying gene mutation. A variety of surgical procedures have been employed to remedy hereditary multiple exostoses such as osteochondroma excision, bone lengthening, corrective osteotomy and hemiepiphysiodesis. Sometimes a combination of the previous procedures is used. The indicators of surgical success in regard to disease and patient characteristics are greatly disputable. Because most studies of hereditary multiple exostoses are retrospective and of limited sample size with missing data, the best evidence for each of the currently practiced surgical procedures is lacking.

Synovial chondromatosis Medical condition

Synovial chondromatosis is a locally aggressive bone tumor of the cartilaginous type. It consists of several hyaline cartilaginous nodules and has the potential of becoming cancerous.

Synovectomy is a procedure where the synovial tissue surrounding a joint is removed. This procedure is typically recommended to provide relief from a condition in which the synovial membrane or the joint lining becomes inflamed and irritated and is not controlled by medication alone. If arthritis is not controlled, it can lead to irreversible joint damage. The synovial membrane or "synovium" encloses each joint and also secretes a lubricating fluid that allows different joint motions such as rolling, folding and stretching. When the synovium becomes inflamed or irritated, it increases fluid production, resulting in warmth, tenderness, and swelling in and around the joint.

Proteoglycan 4

Proteoglycan 4 or lubricin is a proteoglycan that in humans is encoded by the PRG4 gene. It acts as a joint/boundary lubricant.

Meniscus tear Rupturing of the fibrocartilage strips in the knee called menisci

A tear of a meniscus is a rupturing of one or more of the fibrocartilage strips in the knee called menisci. When doctors and patients refer to "torn cartilage" in the knee, they actually may be referring to an injury to a meniscus at the top of one of the tibiae. Menisci can be torn during innocuous activities such as walking or squatting. They can also be torn by traumatic force encountered in sports or other forms of physical exertion. The traumatic action is most often a twisting movement at the knee while the leg is bent. In older adults, the meniscus can be damaged following prolonged 'wear and tear'. Especially acute injuries can lead to displaced tears which can cause mechanical symptoms such as clicking, catching, or locking during motion of the joint. The joint will be in pain when in use, but when there is no load, the pain goes away.

Mesenchymal stem cells (MSCs) are multipotent cells found in multiple human adult tissues including bone marrow, synovial tissues, and adipose tissues. Since they are derived from the mesoderm, they have been shown to differentiate into bone, cartilage, muscle, and adipose tissue. MSCs from embryonic sources have shown promise scientifically while creating significant controversy. As a result, many researchers have focused on adult stem cells, or stem cells isolated from adult humans that can be transplanted into damaged tissue.

Gene therapy is being studied as a treatment for osteoarthritis (OA). Unlike pharmacological treatments which are administered systemically, gene therapy aims to establish sustained, synthesis of gene products and tissue rehabilitation within the joint.

Trapeziometacarpal osteoarthritis Medical condition

Trapeziometacarpal osteoarthritis, also known as osteoarthritis at the base of the thumb or as rhizarthrosis, is a reparitive joint disease affecting the first carpometacarpal joint (CMC1). This joint is formed by the trapezium bone of the wrist and the first metacarpal bone of the thumb. Because of its relative instability, this joint is a frequent site for osteoarthritis. Carpometacarpal osteoarthritis of the thumb occurs when the cushioning cartilage of the joint surfaces wears away, resulting in damage of the joint.

High tibial osteotomy is an orthopaedic surgical procedure which aims to correct a varus deformation with compartmental osteoarthritis. It is usually reserved for younger patients who are generally more active.

The treatment of equine lameness is a complex subject. Lameness in horses has a variety of causes, and treatment must be tailored to the type and degree of injury, as well as the financial capabilities of the owner. Treatment may be applied locally, systemically, or intralesionally, and the strategy for treatment may change as healing progresses. The end goal is to reduce the pain and inflammation associated with injury, to encourage the injured tissue to heal with normal structure and function, and to ultimately return the horse to the highest level of performance possible following recovery.

Hip pain

Pain in the hip is the experience of pain in the muscles or joints in the hip/ pelvic region, a condition commonly arising from any of a number of factors. Sometimes it is closely associated with lower back pain.

A disease-modifying osteoarthritis drug (DMOAD) is a drug that would inhibit or even reverse the progression of osteoarthritis. Since the main hallmark of osteoarthritis is cartilage loss, a typical DMOAD would prevent the loss of cartilage and potentially regenerate it. Other DMOADs may attempt to help repair adjacent tissues by reducing inflammation. A successful DMOAD would be expected to show an improvement in patient pain and function with an improvement of the health of the joint tissues.


  1. Fuller E, Bharatha A, Yeung R, Kassel EE, Aviv RI, Howard P, Symons SP. Case of the month #166: synovial chondromatosis of the temporal mandibular joint. Canadian Association of Radiologists Journal. 2011 May; 62(2):151-153.
  2. "Chondrosarcoma". The Lecturio Medical Concept Library. Retrieved 8 July 2021.
  3. "Synovial Chondromatosis". Genetic And Rare Disease Information Centre. Retrieved 8 July 2021.

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