A 30-year-old female presents with left second finger pain with overlying erythema, warmth, and swelling the day after her cat bit her finger. She cannot fully extend the finger, it is tender and she has pain when it is passively extended. Her hand appears as shown above (Figure 1. Case courtesy of Kristina Kyle, MD).


Pyogenic Flexor Tenosynovitis (FTS) is an acute synovial space infection involving the flexor tendon sheath. Prevalence is estimated between 2.5 and 9.4% [1,2].

  • Pearl: Often, there is no finding on the x-ray other than soft tissue swelling noted.
Sausage digit

Figure 2: Another view of the affected 2nd digit of the left hand with fusiform swelling and less notably finger maintained in passive flexion. Case courtesy of Kristina Kyle, MD.

soft tissue swelling

Figure 3: Radiograph of the hand demonstrating only soft tissue swelling. Case courtesy of Kristina Kyle, MD.

The typical presentation shows a flexed ‘sausage’ finger that progressed rapidly over 1-2 days and has warmth and palmar erythema. The 4 Kanavel signs are often used to evaluate FTS:

  1. Finger maintained in passive flexion
  2. Pain elicited with passive extension
  3. Tenderness along the flexor tendon sheath
  4. Fusiform swelling also referred to as ‘sausage digit’ [3]
  • Pearl: The Kanavel signs have shown high sensitivity (between 91.4% and 97.1%) but low specificity (51.3% to 69.2%) in detecting FTS, so be sure to consider the whole clinical picture [4].

Urgent Orthopedics consult. If FTS is suspected, surgical intervention is required for incision and drainage with culture-specific IV antibiotics [5].

  • Pearl: Some studies have suggested initial nonoperative management with IV antibiotics, immobilization & elevation. However, if no clinical improvement at 24 hours, surgery is still required [6].
  • Pearl: Staph aureus (40-75%) is the most common cultured bacteria, with MRSA accounting for 29%. Other common organisms include Eikenella in human bites and Pasteurella multocida in animal bites [7].

The flexor tendon sheaths are contiguous with other deep spaces of the hand. These anatomic pathways facilitate rapid spread of the infection as it follows the path of least resistance [8].

  • Pearl: Delay in diagnosis or presentation is associated with increased complications such as stiffness, tendon necrosis and rupture, osteomyelitis, deformity, and even amputation, so have a low threshold to consult early [9,10].
Ultrasound. This is particularly useful early in the course when differentiation can be difficult [11].

Figure 4: Transverse views of palm, MCP, PIP, and DIP moving top left to right bottom respectively. Demonstrates diffuse synovial thickening with mild effusion involving flexor digitorum tendons. Case courtesy of Dr. Maulik S Patel, Radiopaedia.org, rID: 48661.

Figure 5: Longitudinal view of the same finger in image 4 again demonstrating diffuse synovial thickening with mild effusion involving flexor digitorum tendons. Case courtesy of Dr. Maulik S Patel, Radiopaedia.org, rID: 48661.


Resources & References:

Check out ALiEM’s Ultrasound for the Win to review some more tips and tricks for making the diagnosis. 

  1. Weinzweig N, Gonzalez M. Surgical infections of the hand and upper extremity: a county hospital experience. Ann Plast Surg. 2002;49(6):621-627. PMID: 12461446.
  2. Glass KD. Factors related to the resolution of treated hand infections. J Hand Surg Am. 1982;7(4):388-394. PMID: 7119400.
  3. Clark DC. Common acute hand infections. Am Fam Physician. 2003;68(11):2167-2176. PMID: 14677662.
  4. Kennedy CD, Lauder AS, Pribaz JR, Kennedy SA. Differentiation Between Pyogenic Flexor Tenosynovitis and Other Finger Infections. Hand (N Y). 2017;12(6):585-590. PMID: 28720000.
  5. Draeger RW, Bynum DK Jr. Flexor tendon sheath infections of the hand. J Am Acad Orthop Surg. 2012;20(6):373-382. PMID: 22661567.
  6. DiPasquale AM, Krauss EM, Simpson A, Mckee DE, Lalonde DH. Cases of Early Infectious Flexor Tenosynovitis Treated Non-Surgically With Antibiotics, Immobilization, and Elevation. Plast Surg (Oakv). 2017;25(4):272-274. PMID: 29619351.
  7. Flevas DA, Syngouna S, Fandridis E, Tsiodras S, Mavrogenis AF. Infections of the hand: an overview. EFORT Open Rev. 2019;4(5):183-193. Published 2019 May 10. PMID: 31191986.
  8. Rigopoulos N, Dailiana ZH, Varitimidis S, Malizos KN. Closed-space hand infections: diagnostic and treatment considerations. Orthop Rev (Pavia). 2012;4(2):e19. PMID: 22802987.
  9. Kennedy CD, Huang JI, Hanel DP. In Brief: Kanavel’s Signs and Pyogenic Flexor Tenosynovitis. Clin Orthop Relat Res. 2016;474(1):280-284. PMID: 26022113.
  10. Stern PJ, Staneck JL, McDonough JJ, Neale HW, Tyler G. Established hand infections: a controlled, prospective study. J Hand Surg Am. 1983 Sep;8(5 Pt 1):553-9. PMID: 6355263.
  11. Jardin E, Delord M, Aubry S, Loisel F, Obert L. Usefulness of ultrasound for the diagnosis of pyogenic flexor tenosynovitis: A prospective single-center study of 57 cases. Hand Surg Rehabil. 2018;37(2):95-98. PMID: 29396150.
Jennifer RaaeNielsen, MD

Jennifer RaaeNielsen, MD

Emergency Medicine Resident
Loma Linda University Medical Center
Jennifer RaaeNielsen, MD

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Mark Hopkins, MD

Mark Hopkins, MD

Loma Linda University Health
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Alexander J. Tomesch, MD

Alexander J. Tomesch, MD

Primary Care Sports Medicine Fellow
Department of Orthopedic and Sports Medicine
University of Arizona - Tucson
Alexander J. Tomesch, MD

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