The formation of fluid in the knee occurs most of the time following a blunt trauma and manifests itself with swelling of the area and pain in the knee which can also be quite acute up to limiting movement, especially in the act of extending the leg or to take weight when standing or while walking.
It is not necessary to be frightened if following a slight trauma the knee appears swollen and painful, most of the time it is a temporary condition that tends to resolve itself spontaneously with some appropriate medication. Spilling of fluid in the
kneeit is not always and only the result of a trauma to damage to the joint, in fact it can be a consequence of multiple factors, which can be of a systemic nature, linked to the habits of the subject, wear and tear and the presence of pathologies.
The most spontaneous question then arises: when it is necessary to consult a doctor
If the swelling occurs after a mild and moderate trauma, severe pain in the knee can also be felt , which is generally soothed by applying ice or ointments to based on painkillers.
In these cases, it is perfectly normal to feel a sensation of pain and swelling that causes difficulty in the extension and loading movement of the leg. If this situation does not resolve itself in a short time, it is advisable to contact your doctor for further diagnostic investigations.
If, on the other hand, the symptoms appear following a strong trauma (or on the contrary, without a triggering trauma), if the pain is very intense, if the swelling does not tend to decrease and if there are skin manifestations on the knee and leg it is necessary to resort to medical intervention as quickly as possible. This is in order to avoid or minimize repercussions on the mobility of the joint or to effectively counteract the pathological processes at the origin of the symptoms.
At this point it seems useful to provide some hints on the anatomy of the knee to better understand the injury mechanisms that cause the formation of fluid in the knee and how they can compromise its functionality.

How the knee is made up
The knee is a leg joint made up of 3 bones: the femur, the patella and the tibia. These form two joints, the femur-tibia joint which has the function of loading and the femur-patella joint which has a sliding and sliding function. The cartilage component of which the menisci
are part is added to the bone componentwhich are interposed between the tibia and the femur which have the function of reducing friction and cushioning both the stresses and the impacts on the knee and leg.
The knee also includes the tendons that have the function of fixing the muscles (biceps and quadriceps muscle) to the bones and the ligaments that have the function of giving stability to the joint and which are divided into:

  • Anterior and posterior cruciate ligament : these two ligaments cross and take the shape of an “x”. Their function is to prevent movements that would lead to dislocation of the knee in an anterior and posterior direction;
  • Lateral and medial collateral ligaments : these ligaments have the function instead of preventing those movements that would lead to the dislocation towards the outside or the inside of the knee.

To these structures is also added the synovial membrane which contains the synovial fluid . The latter has the function of reducing friction between the bones of the joint, but when an inflammatory process occurs in the knee , its production increases, leading to swelling of the area leading to a pathology that takes the name of bursitis .

What is the nature of the fluid in the knee?
The fluid contained in the knee can be of different nature depending on the trauma suffered:

  • Blood: constitutes the most classic and widespread example. A blood spill occurs following a trauma of the anterior cruciate ligament (very frequent in those who practice football as a competitive sport) and the injury of the cruciate is accompanied by the rupture of the dense vascular network that is located in the knee. Anterior cruciate injury may in turn be associated with a meniscus injury;
  • Blood with adipose content: this type of content is very often associated with a fracture. This is because the presence of fat is linked to the leakage of the yellow marrow contained within the long bones and flat bones. The presence of adipose substance therefore constitutes the suspicion of a fracture, which must be confirmed by radiography or CT;
  • Serum: often refers to an inflammation of the knee or to an arthritic phenomenon affecting the meniscus.

Let’s turn the page to analyze in detail all the possible causes of the appearance of an effusion of fluid in the knee .

What are the causes of the presence of fluid in the knee
As previously illustrated, the causes that lead to the formation of fluid in the knee are many, some obvious and obvious, others secondary to clinical pictures.

  • Obesity and overweight: in these cases, the subjects concerned exert excessive pressure that burdens the knee causing wear on the cartilages, a factor that leads to swelling;
  • Sport: in subjects who practice intense sessions of physical exercise and sport and frequent wear processes or traumas of the knee are established;
  • Trauma: undoubtedly the most common cause that leads to the formation of fluid in the knee . These can be mild, leading to a moderate increase in synovial fluid , or severe, such as fracture of the patella, rupture of the meniscus, and strain or rupture of the ligaments. Depending on the nature of the lesion, the constituents of the liquid change;
  • Inflammatory diseases: one of the most common forms is tendonitis, inflammation of the tendon often due to excessive physical exertion. However, one of the most clinically relevant forms concerns autoimmune diseases and in particular rheumatoid arthritis, a pathology that affects the joints and requires specific treatments;
  • Systemic diseases: gout is a metabolic disease that leads to the deposition of urate crystals in the joints, especially in the lower limb;
  • Infections ;
  • Cyst ;
  • Tumors: rare occurrence which takes the name of synovoma.

How to accurately diagnose the triggering cause

Fluid in the knee: how to diagnose
it The structure of the knee is extremely complex and therefore requires the careful evaluation of an orthopedic doctor in order to treat the problem without causing further damage.
Following a knee trauma it is recommended to consult a doctor with speed and not to improvise bandages or medicaments on the basis of any article found on the web.
What types of investigations does the doctor perform

As a rule, the visit proceeds following the usual diagnostic procedure of a common specialist visit, therefore it includes a phase of anamnesis in which the information relating to the trauma, pain and movement difficulties of the subject is collected, then moving on to the palpation of the area and finally, to specific diagnostic tests based on the information collected.
The investigation generally starts first from the evaluation of the healthy knee, in fact, it is necessary to take into account the individual variability: the two joints are almost never identical.
Therefore, before evaluating the knee that has been injured, it is good to have a clear picture of the structure of both knees of the patient.
These can have a different laxite, be more or less curved or more or less protruding.
The inspection proceeds by evaluating the state of the knee , therefore if it is swollen (index of effusion ) and if the extent of the swelling is significant compared to the healthy knee.
The so-called patellar ballot is then evaluated to understand whether the swollen appearance of the knee is actually due to the presence of a liquid effusion and the subject is palpated to understand the site of greatest pain or not.
Finally, tests such as radiology and CT are performed to have a clearer view of the extent of the damage.
What therapies and remedies do we have available

What therapies exist for the fluid in the knee
Depending on the extent of the trauma, different therapeutic strategies will have to be implemented, and this decision rests solely with a doctor who specializes in knee care, the only one who possesses the necessary knowledge to treat a site so complex and important.
Let us now analyze the most effective remedies to counteract knee pain and the pouring of fluid into the joint capsule, remembering that every single action taken without adequate medical advice can be extremely dangerous.
What to do in case of mild trauma and knee pain

Most of the time, if the trauma is minor, it is recommended to apply cold packs or ice, allowing the swelling to subside, associating (always and only on medical prescription) anti-inflammatory drugs or painkillers and still a period of rest, essential for not further burden the arch with subsequent strain and trauma.
If symptoms persist, or if the pain is acute and the knee is very swollen , then a knee specialist is required.
The medical intervention depends on the nature of the trauma, the lesions affecting the anatomical structures of the knee, the nature of the liquid effusion, the symptoms felt by the patient and still takes into account the age and general health conditions of the patient.
In the event of an effusion in the knee joint , a procedure called arthrocentesis is generally carried out, which allows the fluid to drain and therefore empty. Arthrocentesis can be performed thanks to an arthroscopy of the joint. How arthroscopy
is performed
It is an invasive procedure performed under local anesthesia (in some cases also spinal) which must, therefore, be performed in a sterile environment and in a suitably equipped structure.
It goes without saying that this procedure should only be performed by an orthopedic doctor. This procedure involves two small cuts made at the knee : one allows the entry of an optical probe that transmits images on a video, while the other access serves to intervene on the lesion, draining the liquid outwards.
Depending on the case, the liquidtaken is analyzed and if a bacterial load is present, an antibiotic therapy will be set up. If, on the other hand, sodium urate crystals are found in the liquid, then the clinical suspicion turns towards a pathology called gout and the therapy must go to treat the pathology triggering the phenomenon.
It is also useful to take a blood sample to check for infections or inflammatory diseases of the autoimmune type that affect the joints, the most clinically interesting form of which is rheumatoid arthritis.
This pathology will be treated with meticulousness to avoid it leading to serious consequences on the patient’s health.
In more serious cases, an operation is carried out by applying a knee prosthesis to replace the entire joint which is now damaged and no longer recoverable.
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