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How To Aspirate or Inject a Prepatellar Bursa


Alexandra Villa-Forte

, MD, MPH, Cleveland Clinic

Reviewed/Revised Apr 2023

Aspiration of the prepatellar bursa is done for diagnostic purposes (eg, particularly to exclude septic bursitis).

The prepatellar bursa lies just below the skin, increasing the risk of skin damage and infection from corticosteroid injection therapy.

Prepatellar bursitis typically manifests with obvious swelling and erythema; thus, ultrasonography for evaluation and needle guidance is usually unnecessary. Extension of erythema beyond the patellar bursa suggests infection.

Indications for Aspirating or Injecting a Prepatellar Bursa

  • Aspiration of effusion to determine cause of bursitis

  • Occasionally for injections of corticosteroid to treat recalcitrant or recurrent noninfectious inflammation

Prepatellar bursal puncture is usually done diagnostically (eg, to diagnose septic or crystal-induced bursitis). Because the prepatellar bursa is the second most common site of septic bursitis, effusion fluid should routinely be sent to the laboratory for cell count and differential, crystal analysis, Gram stain, culture, and sensitivity tests.

Corticosteroid injection is rarely necessary in the prepatellar bursa. Therapeutic injection should be done only if all of the following criteria are satisfied:

  • Infection has been excluded by bursal fluid analysis.

  • Bursal fluid repeatedly reaccumulates.

  • Symptoms are not relieved by local measures such as ice, elevation, elastic bandage, and nonsteroidal and anti-inflammatory drugs.

When needed, bursal injection may provide rapid relief, which is particularly beneficial for large or painful recurrent effusions.

Contraindications to Aspirating or Injecting a Prepatellar Bursa

Absolute contraindications

  • Hypersensitivity to an injected substance

  • For corticosteroid injection, suspected septic bursitis

Inserting a needle through obviously infected skin should be avoided when possible, but if septic bursitis is suspected, fluid should be aspirated.

Relative contraindications

  • Poorly controlled diabetes: Any benefit of corticosteroids is weighed against risk of worsening glycemic control and risk of infection.

  • Recent (ie, within the last 3 months) corticosteroid injection into same site (although no evidence has evaluated this practice).

Complications of Aspirating or Injecting a Prepatellar Bursa

Complications are uncommon and include

  • Subcutaneous fat atrophy, skin atrophy and sinus tracts, temporary skin depigmentation, and infection due to superficial (< 0.5 cm deep) corticosteroid injection

  • Painful local reaction thought to result from a chemical synovitis in response to the crystals in the corticosteroid solution (sometimes called postinjection flare) occurring within a few hours of depot corticosteroid injection and usually lasting ≤ 48 hours

  • In diabetic patients, hyperglycemia after a depot corticosteroid injection

Equipment for Aspirating or Injecting a Prepatellar Bursa

  • Antiseptic solution (eg, chlorhexidine, povidone iodine, isopropyl alcohol)

  • Sterile gauze, gloves, adhesive bandage

  • 20-mL syringe with 18- to 20-gauge needle for fluid withdrawal

  • Needle insertion site anesthesia (eg, topical freezing spray and/or injectable 1% lidocaine without epinephrine, in a 3-mL syringe)

  • Optional: For therapeutic injection, 5- to 10-mL syringe with 2 to 3 mL 1% lidocaine (without epinephrine) mixed with injectable depot corticosteroid (eg, triamcinolone acetonide, 20 mg)

  • Hemostat, if switching of syringe while the needle remains inserted is anticipated

  • Some 3-, 5-, and 10-mL syringes

  • For diagnostic aspiration, appropriate tubes for specimen collection, including blood culture bottles

Having an assistant is helpful.

Additional Considerations for Aspirating or Injecting a Prepatellar Bursa

  • For bursal injection, local anesthetic and depot corticosteroid can be mixed in a single syringe. Adding the anesthetic helps confirm good needle placement when injection immediately relieves pain. Adding anesthetic also may decrease the risk of the corticosteroid causing subcutaneous fat atrophy and the risk of postinjection flare.

  • Corticosteroid injection is rarely necessary in the prepatellar bursa (based on an increased risk of infection and skin atrophy and a paucity of data showing improved long-term outcomes).

  • Septic bursitis cannot be ruled out by the initial gross and microscopic examination of the aspirated effusion. Infected fluids (even from Staphylococcus aureus, the most common organism) tend to show a minimal fluid leukocytosis (although the neutrophil percentage is generally high). If the history or physical examination suggests septic bursitis, withhold bursal corticosteroid injection. Septic bursitis requires drainage or sometimes bursal excision in addition to systemic antibiotics.

  • Immediate analgesia after injection of local anesthetic helps confirm correct needle placement and that the prepatellar bursa is the source of pain.

Relevant Anatomy for Aspirating or Injecting a Prepatellar Bursa

  • Fluid in the prepatellar bursa is often loculated, resulting in less fluid accessible for withdrawal than expected. In such cases, ultrasound-guidance for aspiration may be helpful.

Positioning for Aspirating or Injecting a Prepatellar Bursa

  • Position the patient reclined or supine. Comfortably rest the knee, slightly flexed, on a pillow.

  • To avoid vasovagal episodes, avert the patient's head and orient your work area so that the patient does not see the needles.

Step-by-Step Description of Aspirating or Injecting a Prepatellar Bursa

Prepare the site

  • Aspirate at the base of the effusion; avoid an injection trajectory that risks piercing the patella.

  • Prepare the area with antiseptic solution.

  • Spray freezing spray at the needle insertion site until it just blanches and/or inject a skin wheal of local anesthetic (eg, ≤ 1 mL).

Puncture the bursa

Aftercare for Aspirating or Injecting a Prepatellar Bursa

  • A protective compression bandage may prevent reaccumulation of fluid in traumatic bursitis.

  • Prescribe limited activity, ice, elevation, and, if not contraindicated, oral nonsteroidal anti-inflammatory drugs (NSAIDs) until pain subsides.

  • Instruct the patient to return for reassessment to exclude infection if pain is continuously and progressively increasing after several hours or persists for > 48 hours.

Warnings and Common Errors for Aspirating or Injecting a Prepatellar Bursa

  • Do not inject corticosteroids against resistance; if there is resistance, slightly withdraw the needle.

Tips and Tricks for Aspirating or Injecting a Prepatellar Bursa

  • Consider doing ultrasonography if there is no obvious large effusion.

  • When inspecting bursal fluid, consider the following: The blood due to a traumatic needle insertion tends to be nonuniformly bloody and tends to clot. Nontraumatic fluid should be evaluated by polarized light microscopy for the presence of crystals.


  • 1. Yui JC, Preskill C, Greenlund LS: Arthrocentesis and joint injection in patients receiving direct oral anticoagulants. Mayo Clin Proc 92(8):1223–1226, 2017. doi: 10.1016/j.mayocp.2017.04.007

Drugs Mentioned In This Article

Drug Name Select Trade
Betasept, Chlorostat, DYNA-HEX, Hibiclens, Oro Clense , Peridex, Periogard, PerioRx , Perisol
7T Lido, Akten , ALOCANE, ANASTIA, AneCream, Anestacon, Aspercreme with Lidocaine, AsperFlex, Astero , BenGay, Blue Tube, Blue-Emu, CidalEaze, DermacinRx Lidocan II, DermacinRx Lidocan III, DermacinRx Lidogel, DermacinRx Lidorex, DermacinRx Lidotral, DERMALID, Dologesic, Ela-Max, GEN7T, Glydo, Gold Bond, Icy Hot , LidaFlex, LidaMantle, Lido King Maximum Strength, Lidocan, LIDOCANNA, Lidocare, Lidoderm, LidoDose, LidoDose Pediatric, Lidofore, LidoHeal-90, LIDO-K , LidoLite, Lidomar , Lidomark, Lidopin, LidoPure, LidoReal-30, LidoRx, Lidosense 4 , Lidosense 5, Lidosol, Lidosol-50, LIDO-SORB, Lidotral, Lidovix L, LIDOZION, Lidozo, Lidtopic, Lidtopic Max, LMX 4, LMX 4 with Tegaderm, LMX 5, LTA, Lubricaine, Lubricaine For Her, Lydexa, MENTHO-CAINE , Moxicaine, Numbonex, Professional DNA Collection Kit, Proxivol, ReadySharp Lidocaine, RectaSmoothe, RectiCare, Regenecare HA, Salonpas Lidocaine, Senatec, Solarcaine, SOLUPAK, SUN BURNT PLUS, Suvicort, Topicaine, Tranzarel, VacuStim Silver, Xyliderm, Xylocaine, Xylocaine Dental, Xylocaine in Dextrose, Xylocaine MPF, Xylocaine Topical, Xylocaine Topical Jelly, Xylocaine Topical Solution, Xylocaine Viscous, Zilactin-L, ZiloVal, Zingo, Zionodi, ZTlido
Adrenaclick, Adrenalin, Auvi-Q, Epifrin, Epinephrine Professional EMS, Epinephrine Professional with Safety Seal, epinephrinesnap , epinephrinesnap-v, EpiPen, Epipen Jr , Primatene Mist, SYMJEPI, Twinject
Aristocort, Aristocort A, Aristocort Forte, Aristocort HP, Aristo-Pak, Aristospan, Arze-Ject-A, Azmacort, Children's Nasacort Allergy 24HR Nasal Spray, Cinalog, Cinolar, Flutex, Hexatrione, Kenalog, Kenalog in Orabase, Kenalog-10, Kenalog-40, Kenalog-80, Nasacort, Nasacort Allergy, Nasacort AQ, Oralone, SP Rx 228 , Tac-3 , Triacet , Triamonide , Trianex , Triderm , Triesence, XIPERE, Zilretta
NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
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