Radiosynoviorthesis (RSO)




The RSO is a nuclear medicine therapy for the local treatment of painful inflammatory joint diseases (e.g. arthritis, rheumatic fever, painful osteoarthritis). It is successfully used for over 20 years to treat pain.

Inflammed joint - arthritis

In recent years many people suffer from rheumatic or degenerative joint disease. With increasing age especially osteoarthritis becomes one of the "most common and economically important diseases of adults,  whereby" women (23%) are overall more affected often than men (15%). Osteoarthritis (degenerative joint disease) is one of the leading diseases related to sick leave, early retirement, rehabilitation measures, and hospital stays.

This is where the joint nuclear medicine therapy or synovectomy with its extensive arsenal of treatment measures has been a proven and essential instrument for efficient local treatment of inflammatory joint diseases for three decades. It is used particularly when other conservative and surgical procedures fail.


At the German Center for synovectomy, we perform the most radiosynoviorthesis treatments throughout Germany and worldwide (in 2009, 7000 radiosynoviorthesis treatments). Accordingly, extensive is the experience of our well-trained physicians with indications and therapies.

What is a synovectomy?


Die synovectomy is a nuclear medical procedure for the treatment of painful, chronically inflammatory joint diseases, such as rheumatoid arthritis or activated osteoarthritis (osteoarthritis). The term synoviorthesis derives from the Greek words "synovial fluid" (mucosa) and "brace" (restoration). Meant is a substantial reproduction of the original synovium by local application of radiation (also known as non-invasive alternative to surgical synovectomy and synovial membrane removal).

The RSO will be conducted by injecting radioactive substances into painful swollen joints with limited movement. As radioactive substances so- called beta emitters are used (yttrium-90 large joint, rhenium-186 for medium-sized joints and erbium-169 for smaller joints, especially finger joints).



Area of application

Medium to maximum range in tissue



Knee joints

3.6 – 11.0 mm

2.7 days


Shoulder, ellbow, hand, hip and ankle joint

1.2 – 3.7 mm

3.8 days


Finger and toe joints

0.3 – 1.0 mm

9.4 days


In Germany, the RSO may be performed on an outpatient basis since 1993 (Revision of the Directive Radiation Protection in Medicine) feasible. The term "RSO" was coined in 1968 by the Parisian rheumatologists Florian Delbarre by modification of the previously chemical synoviorthesis with cytostatics. Florian Delbarre, a doctor of nuclear medicine, is responsible for the implementation of the RSO.


When is a synovectomy performed?


The RSO is used for painful joint diseases. These include primarily the classical inflammatory rheumatic diseases (e.g. rheumatoid arthritis) and inflammatory joint disease (activated osteoarthritis).

Following is an overview of the most common applications of radiation synovectomy:

  • Activated osteoarthritis (a painful, inflammatory joint disease)
  • Chronic polyarthritis (rheumatoid arthritis)
  • Psoriatic arthritis (psoriasis with inflammatory joint involvement)
  • Joint effusion ("water in the joints") and effusions after previous joint surgery
  • Chronic irritation after implantation of a total endoprosthesis (TEP, artificial joint)
  • Inflammatory joint examinations with rheumatoid arthritis, hemophilia (hemophilia)
  • villonodular synovitis

Whether a synovectomy is appropriate or indicated in your case, will be reviewed as part of a detailed preliminary examination in our practice.

Which joints can be treated by a RSO?

In our practice, we can perform synovectomy on all joints outside of the spine. A prerequisite are that the joint to be treated can be reached with a puncture needle and a sufficient amount of radioactive liquid (radionuclide) can be placed into the joint itself, i.e. can be placed in the capsule (hinge sleeve).


Upper extremities:

  • Shoulder joint
  • Acromioclavicular joint (shoulder-corner hinge)
  • Elbow joint
  • Wrist and carpus
  • Metatarsophalangeal joints
  • Proximal interphalangeal joints
  • Distal interphalangeal
  • Carpometacarpal joint
  • midcarpal joint

Lower limbs:

  • Hip
  • Knee
  • Ankle
  • Subtalar
  • Cuneonavicular Joint
  • Calcaneocuboid Joint
  • Tarsus and hock joints
  • Toe joints (especially the metatarsophalangeal joints)


  • Sternoclavicular joint between sternum and clavicle


How is a synovectomy performed?

The RSO can be an outpatient procedure performed in our practice. The radioactive source is ordered for you in France and can be delivered only on certain days (Wednesday, Thursday, and Friday).



After a disinfection of the skin, the joint will be treated under sterile conditions (sterile gloves, fenestrated drape, sterile, disposable needles, disposable sterile syringes) by puncturing it with a thin needle and a local anesthetic. If an effusion exists, it is aspirated. It is important that the radioactive substance will be injected into the joint cavity completely safe, so that healthy tissue is not destroyed. For this reason, immediately before injection of the radioactive substance (except knee joint) a fluoroscopy (X) is made with a contrast medium. In this way, the correct position of the injection needle into the joint can be checked for the correct position. The radioactive substance prepared for you, will be injected into the joint, usually in conjunction with low cortisone to avoid irritation. The needle is pulled back out, the puncture site sealed with a plaster bandage.




For 48 hours immediately after treatment, it is necessary to immobilization the joint completely with a splint since this allows for preventing any drainage from the injected joint space via the lymphatic. However, strict bed rest is not necessary. Next, the correct distribution of the radioactive substance is measured in the joint by means of a gamma camera (with the exception of the small joints) and recorded with a distribution scintigram. Following it is decided whether dependent from the individual risk, a thrombosis prophylaxis (preventive measures for thrombosis) should be performed. If you have received treatment of hip, knee, or ankle in our practice, you will be taken by us by wheelchair to the car or taxi.


How does a RSO work?

After the injection of an appropriate radioactive substance (radionuclide) into the joint, there is a uniform distribution of the fluid in the joint space. The substances are bound to tiny particles (colloids) and only the superficial cells of the inflamed synovial membrane (synovium) are included, which assures that only here the desired effect takes place. The radiation now triggers an additional inflammation inside the mucosal cell, which causes the superficial, thickened (hypertrophied) cell layers to be destroyed – in other words, we fight fire with fire. The cartilage will not be damaged in this procedure. The irradiation is mainly restricted to the synovial membrane since the radioactive substances used only has a maximum radiation range of a few millimeters in tissue. What type of radionuclide is used depends on the size of the joint.  Yttrium-90 is used for the knee joint, the shoulder joint, and medium-sized joints such as the elbow or ankle;  rhenium-186, for small joints such as finger or toe joints we use erbium-169.  The thickness of the synovial membrane changes depending on the size of the joint. In order to achieve a sufficient radiation effect, various radioactive substances (radionuclides) are used. These differ in their depth of the radiation penetration in the tissue by their physical half-life and by their emitted radiation energy. All three nuclides are beta emitters.

Over time there is a gradual rind-like healing (fibrosis and sclerosis) of the mucosal surface and a decrease of the inflammatory activity of the synovial membrane. As a result, the pain is reduced or eliminated and the joint function is  improved. The effect is usually felt within weeks, but sometimes it takes 3 to 6 months. The final effect can in most patients be judged after about 6 months. It there is not a significant improvement after six months, a second treatment will be discussed.


What preliminary examinations are required prior to performing an RSO?



Before a

synovectomy can be performed successfully, there will be a clarifying special nuclear medical exam  (review of indications). Once you have submitted your information about your disease and the symptoms (history), the implementation of a 2-phase scintigraphy of the joints is usually required. With this type of assessment a highly sensitivity inflammation in a joint or surrounding tissue can be represented very accurately, often months before symptoms and changes are visible radio graphically .

The first phase (early recording) captured the soft tissue of the inflammatory indication. It provides important information about the localization and extent of the joint inflammation and provides important information for planning the following synovectomy. In the second phase (late recording), the entire skeletal system can be represented in about two to three hours (scintigraphy). Apart from valuable secondary information, this allows us to accurately distinguish between inflammatory (arthritis) and bony degenerative (osteoarthritis). If necessary, the preliminary assessment is supplemented by an ultrasound examination of the joints. In conjunction with all findings, the  nuclear medicine physician decides then together with the patient, whether a synovectomy is useful and necessary.

Nuclear medical preliminary assessment:

You will receive an intravenous injection with  a radiolabeled substance that is only a minimal radiation exposure. After a few minutes, a first special soft recording (early recordings) of the diseased joints is made with a gamma camera (here: the knee joint, see photo on the right) (approximately 15-30 minutes). After pausing for  about 2-3 hours,  the delayed imaging (scintigraphy) of the affected joints (here: the knee, see image on the left) are added (duration about 30-45 minutes). Since hardly any patient is comparable to another, in our assessment , the program will be adjusted to reflect individual needs. The nuclear medicine physician will discuss with you in detail.

Please bring on this date any existing X-ray and MNR / MRI images (MRI) and other findings, so that they can be incorporated into the overall assessment. At the same time this will help to avoid unnecessary duplicate examinations.




Ultrasound examination of the joints (musculoskeletal sonography):

Depending on the condition of the affected joints,  it is necessary to perform an additional ultrasound. Routinely the musculoskeletal sonography is used to determine especially diseases of the knee joint, for example, joint effusion, abnormal swellings of the joints, and protrusions of the mucosa joint cavity of the knee (Baker's cyst) In special cases, such a cyst should be aspirated even before the administration of radio-synoviorthesis to avoid a burst (rupture) of the cyst.




Detailed discussion:

At the end of the study, the findings are collected and the nuclear medical treatment options are discussed with you in a personal interview.

You will be informed about the method of treatment, the possible side effects of  radiosynoviorthesis including the necessary intra-articular punctures and injections, as well as the need for immobilization of the joint to be treated.

We ask you to sign a form that documents that you have been informed. You will also have to sign a   consent form for the treatment. After you have signed these documents, we will set an appointment for the treatment. 



What are the side effects?

Any effect may principally be associated with side effects. However, these usually occur only rarely. Late damage due to radioactive contamination could so far not be observed.

After a radiosynovior thesis a so-called radiation synovitis (irritation of the synovial membrane) can occur with a transient slight strengthening of joint problems. This may be noticeable your for some hours during the day by warmth, swelling, and effusion. In addition, a tingling or stinging in the joint might be one of the side effects. You can relieve these symptoms almost entirely with cold compresses or ice packs. Additionally, the immobilization of the treated joint helps to prevent the reactive effusion. If necessary, taking a cortisone-free anti-inflammatory medication may be useful ("NSAIDs" non-steroidal anti-inflammatory drug).

Infectious complications (bacterial infection) through the puncture of the joint are extremely rare, but if the occur, they are very dangerous. An infection of the joint should be suspected if the pain increases greatly after the synovectomy and the joint is particularly strong overheated; redness also indicates an infection. The treating physician should be consulted immediately.

Radiation damage to the skin in the area of ​​the puncture site will be very rare. This may be caused by a reverse flow or back pressing the radioactive substance (radionuclide) from the puncture. In the worst-case scenario, a small, very slowly healing ulcer (radiation necrosis) may then develop, sometimes in the course of weeks or several months. With the immobilization of the joint after the synovectomy this can usually be avoided.

Very rarely, it may come to soft tissue ulcers around the joint (periarticular necrosis) if the injection had not been absolutely safe.

In some cases a febrile reaction was observed after injection of the radiopharmaceutical. In rear cases, there is a lymphedema (fluid accumulation in the soft tissues) of the treated limb.

After a synovectomy of the lower extremity (hip, knee, foot), there is a small risk of developing a blood clot in the vein of the leg (venous thrombosis) as a result of the prescribed immobilization. In patients with corresponding risks, a blood thinner, thrombosis prophylaxis, is injected under the skin (subcutaneously) to prevent such a complication (heparin syringes).

When may RSO not be performed (contraindications)?

There are absolute and relative contraindications that may militate against the performing of a synovectomy. An RSO should not be performed during pregnancy or while breastfeeding. A treatment is ruled out even with the suspicion of a bacterial arthritis or when infections or skin diseases are present in the vicinity of the proposed injection site.  A massive bleeding into the joint such as a ruptured Baker's cyst of the knee (to be clarified in the preliminary study) also rules out the treatment. Treatments in children and adolescents are possible in certain exceptional cases, especially when the benefits of treatment significantly outweigh the potential risks of radiation exposure. In cases of highly advanced joint and bone destruction and increased joint instability, a synovectomy treatment should also be carefully weighed. In these cases, the effect of the radiation synovectomy is rather limited and there is a risk that radionuclide particle are not retained in the joint but rather cause an undesirable side effect by wandering into the blood stream.

Absolute contraindications:

  • Pregnancy and lactation
  • Suspected bacterial joint infection
  • Local infections and skin diseases in the vicinity of the injection site
  • Massive bleeding into the joint
  • Ruptured Baker's cyst of the knee

Relative contraindications:

  • Use in children and adolescents and young adults under the age 20 

  •  Baker's cyst of the knee joint with valve mechanism Advanced joint and bone destruction with joint instability

  • Advanced joint and bone destruction with joint instability

What are important measures after a synovectomy?

The joint is treated e.g. with a splint or sling (shoulder), sometimes by a thick gauze dressing (finger joints) and sedated for 48 hours. A treatment of the joints of the lower body (hip, knee, ankle, and toe joints) means that the relevant limb may not be loaded (or only slightly loaded) 48 hours after the treatment, i.e. the stress should be limited mainly to using the toilet. Patients with increased risk will be administered a thrombosis prophylaxis with heparin.


In case the bandage applied by us should press onto the join or cause pain, you can remove it and apply again yourself. Joints that were not treated can be moved normal. After 48 hours, the radioactive substance is well fixed in the synovial membrane. Immobilization is now no longer required. Splint / sling or bandage can now be removed.

Uncommon side effects can set in during the first few weeks such as increased pressure sensation with swelling, warmth or tingling or stinging in the treated joint. These symptoms  can easily be relieved with cold compresses or even a period of immobilization.

An additional cortisone injection with the scope of the RSO may temporarily increase the blood sugar (diabetes mellitus), so that the insulin dose may have to be increased. Another cortisone effect can be felt by a "flush" (burning redness of the face). Occasionally, it also causes a rise in blood pressure. Both symptoms usually disappear within a few days without a specific therapy or may be treated in some cases with an antihistamine (e.g. Tavegil). If, contrary to all expectations, there is an increased discomfort, so we ask that you first contact us or your family doctor, your  rheumatologist or orthopedic surgeon.

In the first week after treatment you should not stress the treated joint and avoid sports or physiotherapy.

What are the results of the RSO?

The effectiveness of the radiation synovectomy is well documented in many clinical studies. It can be reliably assessed due to the usually slow onset of effect after several months. Approximately 50-80% of patients report a subjective improvement of painful symptoms with a decrease of the inflammatory symptoms after about 3-4 months. It is also important to know that in patients with osteoarthritis (degenerative joint disease) the inflammatory symptoms and pain can be relieved . Osteoarthritis as such cannot be treated by synovectomy. Virgin joints cannot be created. In patients with rheumatism the cause cannot be treated, but the painful symptoms and the inflammation can be relieved. Even a basic treatment can generally not be replaced with a synovectomy.

What else should you know as a patient before having a synovectomy?

Screening and therapy are equally possible for patients insured by the statutory health insurances and for privately insured patients. There will not be any additional costs.

Appointments for a preliminary examination may be scheduled by phone at the above noted phone numbers. Government insured patients need a valid transfer, this is not required for privately insured patients in general.

The therapy or radiation synovectomy can be performed only on certain weekdays. The radioactive substances are expensive. They are individually ordered for you from Paris and delivered right on the day of the treatment. It is therefore very important that you keep your appointment. If you cannot keep your appointment, we ask you to cancel it at least one week in advance.

When you come for treatment, please wear loose and comfortable clothing since it is difficult to apply knee braces in narrow tube pants.

On the day of treatment, and during the first 48-hour of immobilization you may not operate a motor vehicle.  You do need a driver for returning home. The time spent in the practice for the treatment is approximately one hour, the treatment itself takes only a few minutes.

Who pays for the synovectomy (RSO)?

The RSO is a standard benefit  afforded all patients of statutory and private health insurances.