Arthrocentesis, or joint aspiration, is the clinical procedure performed to diagnose and, in some cases, treat musculoskeletal conditions. The procedure entails using a

syringe A syringe is a simple reciprocating pump consisting of a plunger (though in modern syringes, it is actually a piston) that fits tightly within a cylindrical tube called a barrel. The plunger can be linearly pulled and pushed along the inside ...

to collect

synovial fluid Synovial fluid, also called synovia, elp 1/sup> 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 articul ...

from or inject medication into the joint capsule. Laboratory analysis of synovial fluid can further help characterize the diseased joint and distinguish between

gout Gout ( ) is a form of inflammatory arthritis characterized by recurrent attacks of pain in a red, tender, hot, and Joint effusion, swollen joint, caused by the deposition of needle-like crystals of uric acid known as monosodium urate crysta ...

arthritis Arthritis is a general medical term used to describe a disorder that affects joints. Symptoms generally include joint pain and stiffness. Other symptoms may include redness, warmth, Joint effusion, swelling, and decreased range of motion of ...

, and synovial infections such as

septic arthritis Acute septic arthritis, infectious arthritis, suppurative arthritis, pyogenic arthritis, osteomyelitis, or joint infection is the invasion of a joint by an infectious agent resulting in joint inflammation. Generally speaking, symptoms typica ...

Uses

In general, arthrocentesis should be strongly considered if there is suspected trauma, infection, or effusion of the joint.

Diagnostic

Arthrocentesis can be used to diagnose

or crystal arthropathy. In the case of a septic joint, arthrocentesis should preferably be performed prior to starting treatment with antibiotics, in order to ensure a proper sample of

is obtained.

Synovial Fluid Analysis

Patients with a fever, suspected flare of existing arthritis, or unknown cause of

joint effusion A joint effusion is the presence of increased intra-articular fluid. It may affect any joint. Commonly it involves the knee (see knee effusion). Diagnostic approach The approach to diagnosis depends on the joint involved. While aspiration ...

should undergo arthrocentesis with synovial fluid analysis. Samples of synovial fluid can be analyzed for gross appearance, presence of crystals, white blood cell count with differential, red blood cell count, and bacterial culture. Normal synovial fluid should not have any cells or crystals present and should appear colorless and clear. * Gross Appearance: Opaque-appearing synovial fluid may indicate the presence of white blood cells, red blood cells, or acellular material such as lipids. Yellow-green appearing synovial fluid may indicate the presence of inflammation or infection. In the case of an infection or septic arthritis, the synovial fluid may contain pus and be more viscous. * Crystal Analysis: Using a microscope and polarizing light filter, birefringence of crystals can be detected in a sample of synovial fluid. This is essential to distinguish monosodium urate crystals in

from calcium pyrophosphate dihydrate crystals in pseudogout. * Cell Count and Differential: In cases of bacterial joint infections, synovial fluid will typically show white blood cell counts of 50,000 to 150,000 cells/mm³. Cases of inflammatory arthritis are also likely to have an elevated white blood cell count in the synovial fluid, although the count will typically be lower than that seen in septic arthritis.

Therapeutic

Aspiration of synovial fluid in cases of

hemarthrosis Hemarthrosis is a bleeding into joint spaces. It is a common feature of hemophilia. Causes It usually follows injury but occurs mainly in patients with a predisposition to hemorrhage such as those being treated with warfarin (or other anticoagu ...

can help reduce pressure around the joints, thus providing pain relief.

Corticosteroid Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are invo ...

medications may also be injected into the joint capsule to provide pain relief and anti-inflammatory effects, especially for

rheumatoid arthritis Rheumatoid arthritis (RA) is a long-term autoimmune disorder that primarily affects synovial joint, joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and h ...

and less commonly

osteoarthritis Osteoarthritis is a type of degenerative joint disease that results from breakdown of articular cartilage, joint cartilage and underlying bone. A form of arthritis, it is believed to be the fourth leading cause of disability in the world, affect ...

. Care should be taken to ensure sepsis has been ruled out before injecting corticosteroids, as doing so may worsen the joint infection. Less commonly, recurrent joint aspirations may be performed for cases of

Procedure

Ultrasound Ultrasound is sound with frequency, frequencies greater than 20 Hertz, kilohertz. This frequency is the approximate upper audible hearing range, limit of human hearing in healthy young adults. The physical principles of acoustic waves apply ...

is often used in conjunction with arthrocentesis to help identify appropriate anatomic markers of the joint. Typically, a 22 gauge needle is used along with a 5 mL syringe, but the sizes can be modified depending on the size of the joint that the procedure is being performed on.

Complications

Inserting a needle into a joint to aspirate fluid may cause an infection of the joint and lead to

. The estimated frequency of this infectious complication is 1 in 3000 procedures. This complication can be prevented by following proper sterile technique, including but not limited to: sterilizing the skin with antiseptic prior to the procedure and sterilizing the tops of medication vials with alcohol wipes prior to drawing up the medication with a syringe. If proper technique is not followed, damage may occur to the

tendon A tendon or sinew is a tough band of fibrous connective tissue, dense fibrous connective tissue that connects skeletal muscle, muscle to bone. It sends the mechanical forces of muscle contraction to the skeletal system, while withstanding tensi ...

nerve A nerve is an enclosed, cable-like bundle of nerve fibers (called axons). Nerves have historically been considered the basic units of the peripheral nervous system. A nerve provides a common pathway for the Electrochemistry, electrochemical nerv ...

s, and

cartilage Cartilage is a resilient and smooth type of connective tissue. Semi-transparent and non-porous, it is usually covered by a tough and fibrous membrane called perichondrium. In tetrapods, it covers and protects the ends of long bones at the joints ...

surrounding the joint being aspirated. Using ultrasound guidance and having a rheumatologist perform the procedure can prevent tendon rupture and neurovascular damage from occurring.

References

External links

* http://www.medicinenet.com/joint_aspiration/article.htm {{Bone, cartilage, and joint procedures Medical treatments