What is arthritis?
Arthritis is the medical terminology for inflammation of the joints. There are many kinds of arthritis, like osteoarthritis which takes place with age (with increasing age, the bone cells start to degenerate on its own), septic arthritis (when bacterial or viral infection affects the joints), psoriatic arthritis (the kind of inflammation that occurs when one has psoriasis), and rheumatoid arthritis among others. According to statistics from the CDC (Center of disease Control), almost 1.5 million people are suffering from rheumatoid arthritis in the United States alone. Rheumatoid arthritis is a kind of autoimmune disease that affects the joints along with other parts of the body. The major complaints of this disease are pain, swelling and limited motion of the affected joints.
What is Arthrocentesis?
Arthrocentesis is removal of the fluid present in the synovial cavity. The synovial cavity is the space between the joints covered the fibrous capsule. This can be done for therapeutic or diagnostic purposes. For diagnostic purposes, the synovial fluid is aspirated to check the cause of inflammation. In therapeutic purposes, administration of medication allows drainage in case of septic arthritis, and to decrease pain. This procedure should be done very carefully to not injure tendons, nerves and blood vessels. Therefore, proper anatomy of the joint capsule needs to be recognized. Sometimes clinicians prefer ultrasound guided arthrocentesis to prevent any damage.
Indications and contraindications to arthrocentesis-
As already stated arthrocentesis can be used for diagnosis and treatment . It is used to evaluate a range of diseases affecting the joints like mono-articular arthritis (inflammation of one joint), septic arthritis (fluid after aspiration is sent to a microbiological examination), joint effusion (increased synovial fluid quantity), and for detecting fractures that took place inside the capsule, and for recognizing crystal arthropathy. Arthrocentesis also helps relieve pain by aspirating fluid and blood, and administrating medications for drainage of septic fluid. There are some medical conditions in which arthrocentesis cannot be done like cellulitis overlying the joint, skin lesions in the joint, bacteremia (bacteria in blood, also known as sepsis), osteomyelitis (inflammation of bone and marrow), coagulopathy (blood coagulation) and joint prosthesis (joint replacement).
The patient has to be prepared before the procedure, procedural sedation or anesthesia may be required and the skin is prepared by antiseptic liquids and all hair should be removed. There are different approaches for arthrocentesis like parapatellar, suprapatellar and infrapatellar. Generally, the parapatellar approach is chosen and the insertion site is fixed. A sterile 20 ml syringe has to be used to aspirate the fluid. It is advisable to keep an extra syringe in case of extra fluid. It is done by stretching the skin over the joint, then the needle is inserted rapidly and finally the fluid is aspirated. The muscles around the knee has to be relaxed for better insertion.
Parapatellar approach- In this approach the lateral or medial border of the joint has to be detected and then the midpoint has to be identified. The needle has to be inserted underneath the middle point in a perpendicular direction.
Suprapatellar approach- For this one, the superomedial or superolateral border is used, the midpoint is marked and the needle is inserted into the suprapatellar bursa. But it has been shown that the suprapatellar bursa has no connection with the knee joint in 18% of the population.
Infrapatellar approach- In this approach, the needle is inserted about 5 mm below the inferior border of the patella (the bone in the knee joint), and a clinician should be careful not to damage the patellar tendon.
After the procedure, the needle has to be taken out briskly, and the area of the joint should be covered with a bandage.
Since the procedure is invasive, it involves certain complications like mechanical damage of the cartilage, improper needle insertion (when the needle damages nerves and blood vessels), hemarthrosis (problem with blood coagulation in the joint) and infection if rules of asepsis and antisepsis are not followed.