Metatarsophalangeal arthrocentesis is a critical diagnostic tool in the setting of acute monoarticular arthritis. Joint aspiration is useful for distinguishing inflammatory from noninflammatory musculoskeletal disorders and is the test of choice to rule out septic arthritis. It also is an effective therapeutic option for pain relief, drainage of a septic effusion, or injection of medications. When done properly and with aseptic technique, it is a safe and well-tolerated procedure that is associated with a low frequency of adverse events. 
The clinician performing the procedure should be familiar with the anatomy of the involved joint in order to avoid puncture of tendons, blood vessels, and nerves. The metatarsophalangeal joint line is located at the base of the metacarpal on the extensor surface of the foot. It can be distracted by applying gentle passive flexion while extending the toe.
Diagnostic indications for metatarsophalangeal arthrocentesis include the following:
Evaluation of monoarticular arthritis
Evaluation of suspected septic arthritis
Evaluation of joint effusion
Therapeutic indications for metatarsophalangeal arthrocentesis include the following:
Relief of pain by aspirating effusion or blood
There are no absolute contraindications to metatarsophalangeal arthrocentesis. Relative contraindications include the following  :
Overlying cellulitis of the joint
Skin lesion or dermatitis overlying the joint
Consider hospitalization if arthrocentesis is performed for the administration of intravenous (IV) antibiotics.
When there is a high probability of a septic joint, the joint should be aspirated regardless of bacteremia or septicemia of the patient.
Joint prosthesis is preferably aspirated by an orthopedic surgeon.
Proper skin cleansing and use of aseptic technique minimize the risk of introducing infection into a sterile joint.
Potential damage to cartilage can be minimized by understanding the joint anatomy and avoiding further advancement of the needle into the joint space once synovial effusion enters the syringe. 
Hemarthroses are typically small and self-limited and require only observation. Hemarthrosis in patients with coagulopathy requires correction of the coagulopathy in consultation with a hematologist.
When arthrocentesis is performed through infected skin for the diagnosis of a potentially septic joint, IV antibiotics should be given immediately following the procedure. The patient should be hospitalized for continuation of antibiotics.
Pain may occur, as with any musculoskeletal procedure.