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Digital sheath: tenosynovitis


Synonym(s): Windgall


  • Inflammation of synovial membrane of digital flexor tendon sheath +/- fibrous layer.
  • Cause: idiopathic, traumatic, chronic fibrosis and synovial proliferation, septic, injuries to SDFT/DDFT/sesamoidean ligaments.
  • Signs: localized swelling of the palmar/plantar aspect of the fetlock region between the suspsensory ligament and flexor tendons and plantar/palmar pastern (digital flexor sheath) +/- lameness, local heat, pain, wound, discharge.
  • Diagnosis: ultrasonography, synovial fluid analysis, radiography, perineural and intrathecal local anesthesia, tenosynovioscopy.
  • Treatment: rest, anti-inflammatories, controlled exercise program; drainage, lavage and antibiotics; intrathecal corticosteroids and hyaluronate; tenosynovioscopy.
  • Prognosis: guarded to poor.



  • Idiopathic: ? etiology:
    • Foals may be born with the condition.
    • Common in adults, especially older animals and usually insidious in onset; ? chronic low-grade trauma or wear and tear.
    • Digital flexor tendon sheaths bilaterally most commonly affected (windpuffs, windgalls).
  • Acute non-infectious: 
    • Traumatic synovitis/capsulitis of sheath lining. Leads to contusions and/or tearing of the synovial membrane with intrathecal hemorrhage and acute inflammation. The latter leads to hyperemia, edema and thickening of the synovium. Trauma may be from kicks, falls and knocks, or from low grade repetitive trauma with normal exercise.
    • Abnormal forces outside of normal range, ie hyperextension, can lead to damage either as one-off severe forces or repetitive lower level forces over time.
    • Complicated or secondary cases are caused by damage to other structures and these are common. Damage inside the sheath may be to the visceral or parietal sheath lining, the mesotendon and vincula, and the SDFT/DDFT and manica flexoria. Extra sheath damage triggering tenosynovitis and may derive from the sheath capsule, the palmar and digital annular ligaments, the phalanges and the proximal sesamoid bones. Continuous irritation and inflammation in the synovium. if unchecked can lead to chronic changes and complex tenosynovitis with synovial proliferation, permanent thickening and fibrosis in the sheath wall and PAL, subcutaneous fibrosis, and fibrous adhesions between structures and the sheath wall.
    • Direct blunt trauma to the sheath    Digital sheath: septic tenosynovitis 01    Digital sheath: septic tenosynovitis 02   by overreaches, resulting in tears of sheath +/- digital flexor tendons.
    • Sympathetic sheath tenosynovitis associated with areas of inflammation in the immediately adjacent parts of the distal limb.
  • Chronic:
    • Sequel to unresolved acute tenosynovitis.
    • Insidious chronic repetitive trauma to sheath wall and internal structures.
    • Complications of co-existing lesions such as:
      • Adhesions between tendons and/or sheath wall.
      • SDFT/DDFT tendinitis.
      • Tears in tendon, manica or sesamoidean ligaments.
      • Thickening and fibrosis of lining and capsule of sheath.
      • Synovial proliferation and masses.
      • Subcutaneous thickening and fibrosis.
      • Annular ligament desmitis with subsequent fibrosis and stenosis of the canal.
  • Septic:
    • Iatrogenic infection.
    • Traumatic injury, eg puncture wounds/lacerations to the palmar/plantar aspect of the distal limb, especially above and below the fetlock    →    introduction of bacteria and/or foreign bodies    →   sepsis.
    • Rarely: hematogenous spread; extension from septic foci within intersesamoidean ligament resulting from septic osteitis of the sesamoid bones.
    • Septic tenosynovitis +/- tendinitis.
    • Possible complications of foreign body material in sheath or adjacent tissues, and osteomyelitis   Bone: osteitis - septic   +/- fractures of the sesamoid bones   Proximal sesamoid: fracture  , or lacerations to the SDFT   SDFT: luxation  /DDFT.


  • Idiopathic: synovial effusion without inflammation, pain, heat or lameness.
  • Acute aseptic: rapidly developing effusion, heat, pain, lameness.
  • Chronic aseptic: persistent synovial effusion, fibrous thickening, +/- stenosis of tendon sheath, +/- adhesion formation, compromised function may eventually   →    annular ligament constriction   Annular ligament: constriction  .
  • Septic: marked synovial effusion; pain; heat; severe lameness; swelling; suppurative synovial fluid; +/- fibrin deposition can rapidly   →    adhesion formation; +/- lysosomal enzymes can   →    tendon digestion   →    degenerative tendon rupture.


  • Acute onset after periods of excessive activity either outside at pasture or ridden/driven exercise.
  • Chronic cases may fluctuate over months with periods of improvement and then recurrence of lameness.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Jordana M et al (2014) Distal limb desensitisation following analgesia of the digital flexor tendon sheath in horses using four different techniques. Equine Vet J 46 (4), 488-493 PubMed.
  • Fiske-Jackson A R et al (2013) The use of intrathecal analgesia and contrast radiography as preoperative diagnostic methods for digital flexor tendon sheath pathology. Equine Vet J 45 (1), 36-40 PubMed.
  • McNally T P et al (2013) Tenosynoviotomy for sepsis of the digital flexor tendon sheath in 9 horses. Vet Surg 42 (1), 114-118 PubMed.
  • Rocconi R A & Sampson S N (2013) Comparison of basilar and axial sesamoidean approaches for digital flexor tendon sheath synoviocentesis and injection in horses. JAVMA 243 (6), 869-873 PubMed.
  • Findley J A (2012) Injuries to the digital flexor tendon sheath in the horse. UK Vet 17, 10-13 VetMedResource.
  • Findley J A, De Oliveira F & Bladon B (2012) Tenoscopic surgical treatment of tears of the manica flexoria in 53 horses. Vet Surg 41 (8), 924-930 PubMed.
  • Arensburg L, Wilderjans H, Simon O, Dewulf J & Boussauw B (2011) Nonseptic tenosynovitis of the digital flexor tendon sehath baused by longitudinal tears in the digital flexor tendons: A retrospective study of 135 tenoscopic procedures. Equine Vet J 43 (6), 660-668 PubMed.
  • Marsh C A, Watkins J P & Schneider R K (2011) Intrathecal deep digital flexor tenectomy for treatment of septic tendonitis/tenosynovitis in four horses. Vet Surg 40 (3), 284-290 PubMed.
  • Crawford A et al (2011) Digital sheath synovial ganglion cysts in horses. Vet Surg 40 (1), 66-72 PubMed.
  • Smith M R et al (2011) Increased cartilage oligomeric matrix protein concentrations in equine digital flexor tendon sheath synovial fluid predicts intrathecal tendon damage. Vet Surg 40 (1), 54-58 PubMed.
  • Smith M R W & Wright I M (2006) Noninfected tenosynovitis of the digital flexor tendon sheath: a retrospective analysis of 76 cases. Equine Vet J 38 (2), 134-141 PubMed.
  • Edinger J, Möbius G & Ferguson J (2005) Comparison of tenoscopic and ultrasonographic methods of examination of the digital flexor tendon sheath in horses. Vet Comp Orthop Traumatol 18 (4), 209-214 PubMed
  • Fraser B S & Bladon B M (2004) Tenoscopic surgery for treatment of lacerations of the digital flexor tendon sheath. Equine Vet J 36 (6), 528-531 PubMed.
  • Schneider R K et al (1992) A retrospective study of 192 horses affected with septic arthritis-tenosynovitis. Equine Vet J 24, 436-442 PubMed.

Other sources of information

  • McIlwraith C W, Nixon A J, Wright I W & Boening K J (2005) Tenoscopy of the Digital Flexor Tendon Sheath. In: Diagnostic and Surgical Arthroscopy in the Horse. 3rd edn. Elsevier Ltd, UK. pp 368-371.
  • McIlwraith C W (2002) Tenosynovitis. In: Adams Lameness in Horses. 5th edn. Lippincott, Williams & Wilkins. pp 630-634.
  • Smith R K W & Webbon P M (1999) Digital Sheath Tenosynovitis. In: Equine Medicine and Surgery. 5th edn. Eds: Colahan P T, Merritt A M, Moore J N & Mayhew I G. Mosby, USA. pp 1575-1577.

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