Arthrocentesis (joint aspiration) is a basic diagnostic tool in the evaluation and treatment of acute joint pathology. [1, 2] It may be performed not also for diagnosis but also for therapy. Synovial fluid analysis allows distinction between inflammatory and noninflammatory conditions and provides direct proof of crystal arthropathy, infection, and hemarthrosis. Synovial aspiration and corticosteroid injections and infiltrations carry minimal risk to the patient when properly indicated and performed.
The wrist joint is anatomically complex (see Wrist Joint Anatomy), but most of the intercarpal spaces communicate with the radiocarpal joint, which may be entered from a dorsal approach. This is, therefore, the preferred site for aspiration of the wrist joint.
Diagnostic indications for wrist arthrocentesis include the following:
Suspicion of septic arthritis  (mandatory)
Suspicion of crystal arthritis or hemarthrosis (strongly advised)
Differentiation of inflammatory and noninflammatory arthritis
Imaging studies (arthroscopy, arthrography)
Aspiration and analysis of synovial fluid are helpful for diagnosis when septic arthritis, crystal synovitis, or bleeding is the suspected cause of a joint, bursal, or tendon sheath condition. In addition, in patients who have poorly defined forms of arthritis, knowledge of the nature of the synovial fluid, particularly the inflammatory cell content, complements findings from the history and physical examination and helps provide the basic framework for diagnosis and treatment (see Table 1 below).
Table 1. Assessment Parameters for Synovial Fluid (Open Table in a new window)
|Parameter||Normal||Osteoarthritis||Rheumatoid and Other Inflammatory Arthritis||Septic Arthritis|
|Total white blood cell count, cells/μL||<200||200-10,000||500-75,000||>50,000|
|Polymorphonuclear cells, %||<25||<50||>50||>75|
Therapeutic indications include the following:
Removal of tense effusions to relieve pain and improve function
Removal of blood or pus from a joint
Injection of corticosteroids and other intra-articular therapies
Lavage of the joint
In patients with tense joint effusions, aspiration of synovial fluid provides prompt relief of pain and permits the patient to move or bear weight on the affected joint. In hemarthrosis or septic arthritis, the blood or pus within a synovial cavity may be damaging to the joint cartilage and synovial membrane. Evacuation of the inflammatory fluid may help ameliorate joint damage. Large articular effusions should be drained as fully as possible to decrease pressure, improve synovial circulation, and prevent muscle atrophy.
Other indications can be for injection in rheumatoid arthritis (RA),  other sterile synovitises, and osteoarthritis (OA). OA can be secondary to calcium pyrophosphate deposition disease (CPPD) or hemochromatosis.
Dorsal wrist tendon pathology
Inflammation and swelling of the extensor tendon sheaths over the dorsal wrist may be due to a number of inflammatory processes (most commonly RA but occasionally crystal-induced arthritis or infectious processes). The areas of swelling are often well defined and close to the surface, and they are easily entered with direct aspiration, usually at a 30-45º angle, with the needle directed along the course of the swollen tendon.
Fluid is often easily obtained. In some patients (those with RA, in particular), proliferative synovial tissue limits the amount of fluid that can be aspirated. After aspiration, the area can be injected with 0.5 mL of corticosteroid mixed with 0.5-1 mL of lidocaine, if indicated.
De Quervain tenosynovitis
De Quervain tenosynovitis, a common overuse syndrome involving the tendons at the radial aspect of the anatomic snuff box, is often helped by local injection of the tendon sheath.
After examination, the area of most tenderness along the course of the tendon should be marked, and the needle should be inserted either proximally or distally, directed almost parallel to the skin. As the needle is advanced, 0.5 mL of steroid with 0.5-2 mL of lidocaine can be injected along the tendon sheath, and a palpable bulge is usually felt along the tendon.
Carpal tunnel syndrome
Inflammation with swelling in the many flexor tendons in the carpal tunnel area may result in median nerve compression (see Carpal Tunnel Syndrome). Injection in this area has the potential to relieve symptoms by reducing this inflammation. This area should be defined by making a mark on the volar aspect of the wrist along the flexor tendons, on the ulnar side of the long palmar tendon, approximately 2.5 cm proximal to the distal wrist crease.
A 22- to 25-gauge needle may be introduced perpendicular to the skin or at an angle of 30º-45º, directed proximally or distally along the course of the tendon. The needle should be introduced about 1.25-2.5 cm, and the area should be injected with 0.5 mL of steroid with 0.5-1 mL of lidocaine. If the needle meets obstruction, or if the patient experiences paresthesias, the needle should be withdrawn and redirected to avoid injection into the body of a tendon or into the median nerve itself.
Small, often hard, nodular structures known as ganglia are frequently present around the hands and wrists, and they may occur in many other areas near joints or tendons. These structures usually contain a thick gelatinous substance that is difficult to aspirate. Although surgical excision may be generally preferable for treatment of wrist ganglia, wrist arthrocentesis and intra-articular steroid injection may be worthwhile options for some patients. [5, 6, 7]
In cases where pain, tendon dysfunction, or nerve entrapment symptoms are bothersome to the patient, aspiration may be attempted, usually with an 18- to 20-gauge needle. Even if no fluid is obtained, the process of puncture occasionally causes the structure to dissipate its contents, and symptoms are relieved. A small amount (0.2-0.5 mL) of steroid with lidocaine may be injected in an attempt to prevent reaccumulation of fluid.
Few absolute contraindications to joint or soft-tissue aspirations and injections exist.
If infection of the joint is suspected, fluid should almost always be aspirated from a joint. For other indications, the procedures should probably be avoided if infection is present in the overlying skin or subcutaneous tissues or if bacteremia is suspected.
The presence of a significant bleeding disorder or diathesis or the presence of severe thrombocytopenia may also preclude joint aspiration. If the procedure is deemed necessary for diagnosis or therapy, it may be carried out with appropriate precautions to address the bleeding disorder (eg, after an injection of factor VIII in a patient with hemophilia). Warfarin anticoagulation with international normalized ratio (INR) values in the therapeutic range is not a contraindication to joint or soft-tissue aspiration or injection.
Arthrocentesis through an area of irregular or disrupted skin (eg, psoriasis) should be avoided because of the increased numbers of colonizing bacteria in such areas.
Aspiration of a joint with a prosthesis in it carries a particularly high risk of infection and is often best left to surgeons using full aseptic techniques.
If infection is the suspected underlying cause of the musculoskeletal problem, corticosteroids should not be injected; if they are, the infection may be exacerbated.