Orthopedics-Online

Knee puncture

definition

In the case of a knee joint puncture, a hollow needle is inserted into the knee joint. More precisely, the needle pierces the joint capsule and is inserted into the cavity of the joint. From there either synovial fluid can be sucked off or medication can be introduced into the joint. The aspirated liquid can be examined and provide information about infections. The suction of the fluid can also be carried out in the case of a joint effusion to relieve symptoms.

Indications

The knee joint puncture can either be performed therapeutically or for diagnostic reasons. For diagnosis, synovial fluid can be aspirated and then assessed bacteriologically and immunologically under a microscope, e.g. Detecting infections or bleeding. In addition, the knee joint can be filled with contrast medium via a puncture to enable an MRI examination.

Therapeutically, the knee joint is punctured to remove medication such as bring in anti-inflammatory steroids or local anesthetics. Another indication would be the suction of an effusion to relax the capsule and thus to reduce pain. A bruise in the joint can also be removed in this way.

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Knee joint effusion - how dangerous is it?

Knee puncture after an operation

After an operation on the knee joint, e.g. A cruciate ligament or meniscus operation can lead to a knee joint effusion. This is due to the tissue damage that occurred in the operating room, which leads to an accumulation of fluid. This can show up in the form of painful swelling or restricted mobility in the joint. If the effusion does not heal within an acceptable period of time by immobilizing, cooling and elevating the effusion, the effusion can be relieved with a knee joint prosthesis.

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The knee joint is one of the joints with the greatest stress.

Therefore, the treatment of the knee joint (e.g. meniscus tear, cartilage damage, cruciate ligament damage, runner's knee, etc.) requires a lot of experience.
I treat a wide variety of knee diseases in a conservative way.
The aim of any treatment is treatment without surgery.

Which therapy achieves the best results in the long term can only be determined after looking at all of the information (Examination, X-ray, ultrasound, MRI, etc.) be assessed.

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Knee puncture after an accident

The puncture after an accident often shows blood, which can indicate that ligaments have been injured or may have been damaged. are torn. If bones or cartilage were also injured in the accident, the synovial fluid often contains not only blood but also fatty components. Overall, the damaged joint is inflammatory changed after the accident, as immune cells migrate into the joint for wound healing. This process also leads to joint effusion, which can show up as swelling or restricted mobility.

How painful is a knee puncture?

The knee joint puncture is almost painless and is described as hardly more painful than taking a blood sample. Local anesthesia is therefore usually not used, since the anesthetic puncture is about as painful as the puncture itself. However, local anesthesia can also be performed if desired.

When introducing medication or contrast media, there may be a feeling of pressure that is not painful.

If there was swelling in advance due to an effusion, the puncture even relieves pressure and reduces pain.

Since general anesthesia is not necessary due to the painlessness, the procedure can also be carried out on an outpatient basis.

Performing the puncture

The knee joint can be performed on an outpatient basis, which means that no hospitalization is necessary.
The knee must be kept free from clothing. As a rule, it is not necessary to shave before the procedure, as this can even encourage infections.

If there is an obstruction due to hair on the knee, it can be shortened slightly with scissors.
The knee is disinfected before the puncture. A brown iodine solution is often used for this. The knee is usually in a stretched position.

The muscles should be completely relaxed. Only with ventral access route, which is often used to introduce medication into the joint space, the patient sits on the edge of the examination table and lets the leg hang down loosely. The knee is bent.

After disinfection, the hollow needle is inserted into the joint space under sterile conditions. This means that only devices that have been thoroughly disinfected are used.
Under certain circumstances, it may be necessary beforehand to visualize the joint with an ultrasound device in order to be able to localize it correctly.
Depending on the question, the doctor either injects the drug or sucks off the synovial fluid. This is then examined in a laboratory for inflammatory cells, blood, antibodies, proteins or other changes.

If you experience symptoms after the injection, the doctor who previously performed the puncture or another doctor should be consulted.

Duration

The knee joint puncture is usually performed on an outpatient basis and does not take very long.If it is just an injection of medication or a removal of little synovial fluid, the puncture only takes a few minutes. If a bruise is suctioned off, the process may take a little longer. It is recommended to keep the knee still for about four to six hours after the puncture. However, exact information can be obtained from the attending physician.

What access routes are there?

Various approaches are suitable for the knee joint function.

Typical are:

the lateral,
the lateral-proximal
or the anterior approach.

In the lateral approach, the knee is in an extended position. The kneecap is raised slightly and the knee is punctured from the side below the kneecap.

A lateral-proximal access route is particularly useful for large joint effusions. This access route is about 1.5 cm laterally above the kneecap.

If the puncture is to be used for injection, the ventral access is usually used.
With this access route, the patient sits optimally on the edge of the couch and lets the leg hang freely. The point is in the middle of an imaginary triangle, the corners of which are formed by the kneecap tendon, the articular process of the thigh, which lies towards the center of the body, and the upper surface of the tibia.

What can you examine?

The joint fluid obtained can first be examined visually for opacity or coloration. This can provide evidence of an inflammatory or traumatic process. Furthermore, the liquid can be analyzed to differentiate between an inflammatory and a non-inflammatory process with regard to the protein content and the number of cells or the types of cells present. For the diagnosis of rheumatic diseases, an immunological test can also be carried out to detect the presence of antibodies.

Results

Yellow liquid

A yellow liquid indicates that no ligaments were injured. If the puncture is yellow and cloudy, it is probably an inflammatory process. However, if the liquid is clear and more amber in color, this indicates a non-inflammatory cause, e.g. osteoarthritis. Osteoarthritis is non-inflammatory wear and tear on the joint.

Cloudy liquid

Cloudy synovial fluid indicates an inflammatory process. This leads to an increase in inflammatory cells. The high cell density in the liquid leads to a cloudy appearance. An inflammatory change in the knee joint can occur in the context of a rheumatic disease (especially psoriatic arthritis) or a bacterial infection, e.g. after an operation or knee joint endoscopy. A gout attack also clouds the synovial fluid.

Bloody liquid

A bloody synovial fluid suggests that ligaments in the knee joint are injured. If the puncture is not only bloody but also covered with fat eyes, this suggests that not only ligaments, but also cartilage and bones are injured. A bloody puncture can also indicate a capsule rupture or a blood clotting disorder. Even after an operation, the puncture is often bloody.

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Bruise in the knee

Risks

infection

The risks of a knee puncture include infections. Bacteria get into the knee joint through the puncture.

Usually these are bacteria that are naturally present on the surface of the skin. The most common bacteria are staphylococci (Staphylococcus aureus). They belong to our so-called physiological skin flora. If the skin is not adequately disinfected before a knee puncture, the bacteria can adhere to the syringe. During the puncture, they get into the knee joint, where they trigger local inflammation.

A sufficiently hygienic disinfection of the puncture site can, however, greatly reduce the likelihood of such an infection, so that knee joint infections only rarely occur due to punctures.

Hemarthrosis

The term hemarthrosis is made up of the two components heme (Greek for blood) and arthrosis (Greek for joint) and thus generally refers to bleeding into a joint.

A hemarthrosis can be detected during the knee puncture. In this case, blood cells can be found in the synovial fluid. Often the cause is traumatic (e.g. a tear in the meniscus or cruciate ligament). Chronic hemarthrosis may have a coagulation disorder. However, bleeding into the knee joint can also occur as a complication of the knee puncture. If a small blood vessel is hit during the puncture, it can bleed into the joint space. The body usually breaks down the blood quickly so that no serious symptoms occur.

Further information on the subject can be found in the following article: Hemarthrosis - what is it?

Contraindications

Marcumar intake

Anticoagulant therapy with Marcumar® is currently not a contraindication for a knee joint removal. In individual cases, coagulation should be checked beforehand using a blood analysis. Marcumar® can lead to increased bleeding or bruising in the joint after the puncture.

According to the current guidelines of the AWMF, only an infection, skin disease or damage to the skin at the puncture site is a contraindication for non-urgent punctures.

How should you behave after a puncture?

The knee puncture is a comparatively harmless medical procedure. As a rule, it can be carried out on an outpatient basis, so that you are immediately mobile again.

Nevertheless, the knee is usually a little weak and painful afterwards. Therefore you should put it up for a few hours and cool it if necessary. Extensive exercise should be started on the following day at the earliest, depending on the symptoms and complications that arise. You should refrain from sporting activities a little longer.

It is also important to observe the knee joint after the puncture. If severe pain or signs of inflammation occur in the knee joint or the puncture site, you should consult a doctor.

When can you start exercising again?

After a knee puncture, we recommend taking a break from exercise of at least a few days. The main concern here is that the irritation caused by the puncture can heal again. Depending on the type of operation, the duration can vary between a few days and a few weeks, so the ability to exercise should definitely be discussed with the responsible doctor.

In the case of knee punctures, however, it is not only the puncture itself that is limiting for a return to sport. Rather, it is also about the underlying disease that makes knee puncture necessary. Here, too, the advice of the attending physician should be sought.

Sick leave after a knee puncture

The knee puncture is a very quick and uncomplicated medical procedure. It usually takes no more than a few minutes. Since the affected leg should be put up for a few hours afterwards, it makes sense to take sick leave for the day of the puncture itself.

How long the sick leave lasts afterwards depends more on the underlying disease than on the puncture itself. If there are no complications such as bleeding or infections after the knee puncture, no lengthy sick leave is necessary. In the case of restrictive knee problems, you should first be on sick leave for a few days up to a week. If necessary, the attending physician can extend the sick leave depending on the symptoms.

How often can you puncture a knee?

Knee punctures should only be performed if there is a clear indication to do so. Otherwise, puncture should be avoided due to the possible complications.

Therefore, the following rule applies: knee punctures are performed as rarely as possible. Nevertheless, there are indications in which multiple punctures are necessary. The first injections are often planned every few weeks, after which it usually takes about 3 months until the next injection or puncture.