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Arthrocentesis Of The Hip


Calvin Eric Hwang, MD CAQ-SM
Clinical Assistant Professor
Department of Orthopedic Surgery
Stanford University School of Medicine


  • Arthrocentesis of the hip should be performed under ultrasound guidance
  • If an effusion is present, hip joint aspiration can be both diagnostic and therapeutic.
  • Emergency Physicians should be familiar with hip arthrocentesis with the use of ultrasound.
Video demonstrating an ultrasound guided hip injection. Note the approach is the same and the needle is well visualized here.


  • The hip joint is a common source of pain and can result from a variety of causes.
  • In the Emergency Department (ED), it is imperative to distinguish infectious from non-infectious causes of hip pain.
  • Timely diagnosis of a septic hip is critical due to risk of joint destruction and hip joint arthrocentesis is the gold standard for diagnosis.
  • Previous studies have described the use of ultrasound guided hip arthrocentesis by emergency physicians.[1]Freeman K, Dewitz A, Baker WE. Ultrasound-guided hip arthrocentesis in the ED. Am J Emerg Med. 2007;25(1):80-86. doi:10.1016/j.ajem.2006.08.002[2]Moak JH, Vaughan AJ, Silverberg BA. Ultrasound-guided hip arthrocentesis in a child with hip pain and Fever. West J Emerg Med. 2012;13(4):316-319. doi:10.5811/westjem.2011.10.6797
  • In addition to aiding in the diagnosis of septic joint, hip joint aspiration may also provide symptomatic relief in some non-infectious causes of hip pain such as transient synovitis.
  • Emergency physicians should be familiar with the technique necessary to perform a hip arthrocentesis.


  • The hip, formally termed the femoroacetabular joint, is a ball and socket joint comprised of the femoral head and the acetabulum.
  • Hip flexion is performed by several muscles, collectively known as hip flexors. They include the iliopsoas, rectus femoris, and sartorius.
  • The joint capsule, deep to the hip flexors anteriorly, begins at the acetabular labrum and extends to the lower femoral neck.
  • Hip joint effusions are best visualized at the anterior synovial recess, which is a potential space between the femoral neck and the capsule.
Illustration of the hip anatomy. Note the capsule (unlabeled) extends down to the lower aspect of the femoral neck.[3]Image courtesy of, “Femoro-Acetabular Impingement (FAI) / Labral Tear”

Ultrasound Evaluation

  • A linear or curvilinear probe, depending on body habitus, should be used for evaluation of the hip joint.
  • Place the probe in short axis over the proximal femoral diaphysis and move it proximally until the greater trochanter comes into view. Rotate the medial aspect of the probe into the plane of the femoral neck and slide the probe medially.
  • The ultrasound probe should be placed in plane with the femoral neck with visualization of the acetabulum, labrum, femoral head/neck, and anterior synovial recess.
  • An effusion, if present, will be readily visible as an anechoic collection just anterior to the femoral neck. A normal anterior synovial recess should measure less than 5 mm.
  • This potential space would also be the target for an injection.
Ultrasound view of a normal hip using the curvilinear probe. From left to right the femoral neck, head and acetabulum are visualized. The capsule is seen above extending from the acetabulum down to the neck. A physiologic amount of hypoechoic fluid is noted.
Ultrasound view of an effused hip. The femoral neck (arrow) and capsule (arrowhead) are marked. There is significant distension of the anterior synovial recess.[4]Boniface, Keith, et al. “Point-of-care ultrasound for the detection of hip effusion and septic arthritis in adult patients with hip pain and negative initial imaging.” The Journal of … Continue reading


  • Landmark vs. Ultrasound Guided Approach
    • Hip arthrocentesis in the ED should always be performed under ultrasound guidance.
    • Ultrasound-guided hip arthrocentesis in the ED has been described extensively in the literature.[5]Minardi JJ, Lander OM. Septic hip arthritis: diagnosis and arthrocentesis using bedside ultrasound. J Emerg Med. 2012;43(2):316-318. doi:10.1016/j.jemermed.2011.09.029[6]Tsung JW, Blaivas M. Emergency department diagnosis of pediatric hip effusion and guided arthrocentesis using point-of-care ultrasound. J Emerg Med. 2008;35(4):393-399. … Continue reading
    • However, Berona et al compared ultrasound-guided vs landmark-guided hip arthrocentesis using a cadaver model.[7]Berona K, Abdi A, Menchine M, et al. Success of ultrasound-guided versus landmark-guided arthrocentesis of hip, ankle, and wrist in a cadaver model. Am J Emerg Med. 2017;35(2):240-244. … Continue reading
    • They noted a trend towards increased success, decreased time to success, and fewer attempts in the ultrasound-guided group compared to the landmark-guided group5. There was a 100% success rate in hip arthrocentesis when performed under ultrasound guidance.
    • Due to the many crucial structures in the hip (femoral artery/vein, femoral nerve, etc), ready availability of ultrasound, and depth necessary to enter the hip joint, landmark guided hip arthrocentesis is strongly discouraged.
  • Materials
    • 18 gauge draw needle
    • 1.5 – 2 inch, 25 gauge needle for local anesthetic administration
    • 3.5 inch, 18 gauge needle for aspiration
    • 5 – 10 cc syringe
    • Local anesthetic
    • Sterile equipment (gauze, skin prep, gloves, probe cover, etc)

Ultrasound Guided Technique

  • General
    • This procedure can be performed without assistance, but an assistant is highly recommended
    • They can can be helpful with larger patients, specifically pannus retraction, help maintain a sterile field, and save appropriate images
    • Procedure should be done with strict sterile technique.
  • Position
    • The patient should be supine with leg flat against the table
  • Ultrasound evaluation
    • Begin by identifying the proximal femoral shaft in short axis.
    • Slide the probe more proximally to identify the greater trochanter. This is noted by a change in the contour of the bone.
    • Rotate the medial aspect of the probe cranially until you begin to visualize the femoral neck, and then slide the entire probe medially at that angle. The probe should approximately be pointed towards the umbilicus.
    • You should now be able to identify the acetabulum, labrum, femoral head/neck, and anterior synovial recess.
    • You will need to rotate the probe and move laterally to medially slowly to identify the best view. If you become disoriented, go back to the starting position of the proximal femoral shaft in short axis.
    • Synovial fluid will appear as an anechoic collection in the anterior synovial recess superficial to the femoral neck.
    • Note: The femoral triangle is very medial to the joint and your needle approach. If you are concerned your needle is going to come close to the femoral triangle, your positioning is incorrect. Reset and obtain a more lateral view for access.
Demonstration of starting probe position with the proximal femoral shaft in short axis. Note this is your reference position if you become disoriented.
Corresponding sonographic view to the starting probe position. The femoral shaft is visualized in short axis.
Demonstration of probe position for procedure located over the long axis of the joint and femoral neck.
Corresponding sonographic view to the procedural position with visualization of the femoral neck, head, acetabulum and capsule.
  • Local anesthetic
    • Under ultrasound guidance, we recommend using a long 25 gauge needle to create a track for the larger 18 gauge needle used for aspiration
  • Under ultrasound guidance
    • The 18 gauge spinal needle should be inserted with direct visualization in long axis into the hypoechoic collection approaching distal to proximal.
    • Avoid any vessels using color doppler as needed
    • Negative pressure with the syringe should be maintained throughout.
  • Aspirate until all visible fluid has been collected.
    • Fluid may be sent for gram stain, culture and fluid/crystal analysis as appropriate
Ultrasound demonstrating the needle in plane in the anterior synovial recess.
Video demonstrating an ultrasound guided hip injection. Note the approach is the same and the needle is well visualized here.
Hip arthrocentesis demonstration by Dr Karkucak. The needle is not well visualized (the top can be seen) but synovial fluid is aspirated and the view is correct (would recommend decreasing depth).

Additional Considerations

  • Benefits
    • Easy to visualize effusion.
    • Procedure is performed with direct needle visualization throughout
    • Arthrocentesis can be both diagnostic and therapeutic.
    • Can speed time to diagnosis and disposition.

Pearls & Pitfalls

  • A 22 gauge or larger spinal needle (2.5” or longer depending on body habitus) should be used. The flexibility of thinner needles makes the procedure more difficult to perform.
  • If indicated, medication (e.g. steroid or anesthetic) can be injected into the hip joint using the same approach.
  • Hip arthrocentesis is more challenging in obese and muscular patients. A curvilinear probe, longer spinal needle, and an assistant to hold pannus can make these patients more manageable.
  • In overweight and obese patients, a large pannus can make the procedure challenging. It is helpful to have a staff member ‘retract the pannus’ in these patients. Some patients may have too much soft tissue, in which case this procedure may be best performed by radiology under fluoroscopy.