Prepatellar Bursal Injection

Other Names

• Prepatellar Bursal Injection
• Prepatellar Bursal Aspiration

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Background

Key Points

• Transducer: high frequency, linear
• Needle: 1.5 inch, 20-22 (injection) or 18 (aspiration)
• In plane approach in either short or long axis

Anatomy of the Prepatellar Bursa

• Tricompartmental structure situated in the subcutaneous tissue anterior to the patella
• Separated by two thin septa oriented in a coronal plane
• The prepatellar bursa does not communicate with the joint space
• The prepatellar bursa is a flat, round, synovial-lined structure

Palpation Guidance vs Ultrasound Guidance

• To date, there are no studies comparing ultrasound and palpation guided approaches to the prepatellar bursa
• Multiple studies have shown that ultrasound improves accuracy when injecting other bursa
• The superficial nature of the prepatellar bursa and lack of neurovascular structures does make it reasonable to approach it with palpation guidance

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Indications

• Prepatellar Bursitis

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Contraindications

• Absolute
  • Anaphylaxis to injectates
  • Overlying cellulitis, skin lesion or systemic infection
• Relative
  • Can be treated with less invasive means
  • Hyperglycemia or poorly controlled diabetes
  • Lack of symptom improvement with previous injection

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Procedure

There is prepatellar fluid with internal fat and thin septa. It measures about 31 x 27 x 5 mm. It is located in the subcutaneous plane and abutts the lower pole of the patella and the upper end of the patellar tendon. The patellar and quadriceps tendons show normal echopattern. There is no suprapatellar effusion

Needle and probe position for short axis, in plane approach

Short axis view with needle approach the prepatellar bursa in plane

Equipment

• Sterile prep (i.e. chloraprep, chlorhexidine, iodine, etc)
• Gloves
• Needle: typically 21-25 gauge, 1.5 inch
• Syringe: 5-10 mL
• Gauze
• Ethyl Chloride
• Bandage
• Injectate
  • Local anesthetic
  • Corticosteroid
• Sterile probe cover

Ultrasound Findings

• Transducer: high frequency, linear
• Dept is 1-3 cm
• Common ultrasound findings include:
  • Distension of bursa
  • Fluid can range from anechoic to hyperechoic to mixed/complex echogenicity
  • Hyperemia of subcutaneous tissue
  • Cobblestoning of subcutaneous fat

Technique: Short Axis, In Plane

• Patient Position
  • Supine, knee flexed to about 30 degrees
  • Place a towel/ rolled up sheet behind the knee
• Transducer position
  • Short axis to the patellar tendon
  • Can confirm in long axis
• Needle Approach/ Orientation
  • In plane
  • Lateral to medial
  • Alternatively, can approach medial to lateral
• Target
  • Prepatellar bursa
• Pearls and Pitfalls
  • Apply gentle pressure, too much can displace the fluid

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Aftercare

• No major restrictions in most cases
• Can augment with ice, NSAIDS
• Consider Knee Compression Sleeve to reduce re-accumulation/ swelling

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Complications

• Infection
• Damage to surrounding tissue

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See Also

• Procedures Main
• Ultrasound Main
• Knee Pain Main

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