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 In anatomy, a joint capsule or articular capsule is an envelope surrounding a synovial joint.gout Gout ( ) is a form of inflammatory arthritis characterized by recurrent attacks of a red, tender, hot and swollen joint, caused by deposition of monosodium urate monohydrate crystals. Pain typically comes on rapidly, reaching maximal intens ...

arthritis Arthritis is a term often used to mean any disorder that affects joints. Symptoms generally include joint pain and stiffness. Other symptoms may include redness, warmth, swelling, and decreased range of motion of the affected joints. In som ...

, and synovial infections such as

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

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

crystal arthropathy Crystal arthropathy is a class of joint disorder (called ''arthropathy'') that is characterized by accumulation of tiny crystals in one or more joints. Polarizing microscopy and application of other crystallographic techniques have improved iden ...

. 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. Diagnostic approach The approach to diagnosis depends on the joint involved. While aspiration of the joint is conside ...

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

gout Gout ( ) is a form of inflammatory arthritis characterized by recurrent attacks of a red, tender, hot and swollen joint, caused by deposition of monosodium urate monohydrate crystals. Pain typically comes on rapidly, reaching maximal intens ...

from calcium pyrophosphate dihydrate crystals in

pseudogout Calcium pyrophosphate dihydrate (CPPD) crystal deposition disease, also known as pseudogout and pyrophosphate arthropathy, is a rheumatologic disease which is thought to be secondary to abnormal accumulation of calcium pyrophosphate dihydrate crys ...

. * 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 anticoagulan ...

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 inv ...

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 joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and hands are inv ...

and less commonly

osteoarthritis Osteoarthritis (OA) is a type of degenerative joint disease that results from breakdown of joint cartilage and underlying bone which affects 1 in 7 adults in the United States. It is believed to be the fourth leading cause of disability in the ...

. 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 waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies ...

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, high-tensile-strength band of dense fibrous connective tissue that connects muscle to bone. It is able to transmit the mechanical forces of muscle contraction to the skeletal system without sacrificing its ability ...

nerve A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system. A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the ...

s, and

cartilage Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck ...

surrounding the joint being aspirated. Using ultrasound guidance and having a

rheumatologist Rheumatology (Greek ''ῥεῦμα'', ''rheûma'', flowing current) is a branch of medicine devoted to the diagnosis and management of disorders whose common feature is inflammation in the bones, muscles, joints, and internal organs. Rheumatolog ...

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