Equis ISSN 2398-2977

Bone: osseous cyst-like lesions

Synonym(s): Subchondral cysts

Contributor(s): Carl Kirker-Head, Graham Munroe




  • Unknown for certain, and under current investigation.
  • Various hypotheses have been suggested.
  • May be similar to true subchondral bone cysts   Stifle: femorotibial subchondral bone cyst  , on the basis that subchondral cystic lesions can occur secondary to anything that causes an articular cartilage and/or subchondral bone defect, eg:


  • Unknown for certain, and under current investigation.
  • Osseous cyst-like lesions occur in variety of locations. 
  • They vary more in structure than true bone cysts   Stifle: femorotibial subchondral bone cyst  , and can be single or less frequently multiple, localized or extensive, single or multi-chambered.
  • They do not always contain a true cystic lining.
  • They may or may not communicate with the joint cavity.
  • Some start as a small elliptical depression in the articular surface which progressively enlarges into the subchondral bone. A sclerotic margin may or may not develop.
  • Lesions close to/involving an articular surface are more likely to be associated with lameness.


  • Caudal femoral condyle:
    • Rare.
    • Foals.
    • Localized or extensive osseous defects.
  • Proximal tibia:
  • Tarsocrural joint:
    • Medial and lateral malleolus.
    • Intertrochlear groove of talus.
    • Distal intermediate ridge of tibia.
  • Fetlock:
    • Particularly distal medial condyle MCIII/MTIII   MCP / MTP joint: subchondral bone cyst 01 - LM radiograph      MCP / MTP joint: subchondral bone cyst 02 - skyline radiograph  .
    • Usually younger horses (1-2 year-olds).
    • Elliptical lucency with progressively increasing sclerotic outline.
  • Carpus:
    • All carpal bones   Carpus: osseous cyst-like lesion 01 - flexed radiograph      Carpus: osseous cyst-like lesion 02 - post mortem  .
    • Proximal MCII/III/IV:
      • Usually non-articular.
      • Often asymptomatic.
    • Distal radius and radial carpal bone (often associated with lameness)   Radius: osseous cyst-like lesion 02 - DP radiograph  :
      • Usually solitary, circular lucent areas.
      • Single or chambered.
      • +/- sclerotic rim.
      • ? associated with trauma or osteochondrosis.
      • +/- communication with antebrachiocarpal joint.
  • Tarsus:
    • Rare.
    • Uni/bilateral.
    • Single lesions.
    • Distal tibia > talus > calcaneus > MTIII.
  • Proximal interphalangeal joint:
  • Distal interphalangeal joint:
    • Midline proximal P3   Distal phalanx: subchondral bone cyst - upright pedal bone radiograph  .
      • Variable connection to articular surface.
      • Usually unilateral and solitary.
      • Often associated with lameness (moderate to severe).
      • Located anywhere from the extensor process (rare) to deep within weight-bearing surface.
      • Access may be difficult for arthroscopy and a portal through the hoof wall may be required.
    • Distal P2 (rare).
  • Elbow:
    • Medially in proximal radial epiphysis   Elbow: osseous cyst-like lesion - CaCr radiograph  :
      • Well-defined.
      • Tend to be associated with new bone in the region of insertion of the medial collateral ligament.
    • Distal humerus (less common):
      • Often large, well-defined lesions.
  • Scapulohumeral joint:
    • Middle of glenoid cavity of distal scapula:
      • ? many are true cyst lesions or deep lysis associated with OCD flap lesions of the glenoid cavity.
    • Humeral head (less common).
  • Coxofemoral joint:
    • Rare.
    • In young horses associated with chronic lameness.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Mair T & Sherlock C (2011) Osseous cyst-like lesions/subchondral bone cysts of the phalanges. Equine Vet Educ 23 (4), 191-204 VetMedResource.
  • Montgomery L J & Juzwiak J S (2009) Subchondral cyst-like lesions in the talus of four horses. Equine Vet Educ 21 (12), 629-637 VetMedResource.
  • Little D, Redding W R & Gerard M P (2009) Osseous cyst-like lesions of the lateral intertubercular groove of the proximal humerus: A report of 5 cases. Equine Vet Educ 21 (2), 60-66 VetMedResource.
  • Mair T S & Sherlock C E (2008) Osseous cyst-like lesions in the feet of lame horses: diagnosis by standing low-field magnetic resonance imaging. Equine Vet Educ 20 (1), 47-56 VetMedResource.
  • Brounts S H, Adams S B, Vemireddi V & Holland C H (2008) A malignant glomus tumor in the foot of a horse. Equine Vet Educ 20 (1), 24-27 VetMedResource.
  • Garvican E & Clegg P (2007) Clinical aspects of the equine carpal joints. UK Vet 12 (1), 5-13 VetMedResource.
  • García-López J M & Kirker-Head C A (2004) Occult subchondral osseous cyst-like lesions of the equine tarsocrural joint. Vet Surg 33 (5), 557 PubMed.
  • Story M R & Bramlage L R (2004) Arthroscopic debridement of subchondral bone cysts in the distal phalanx of 11 horses. Equine Vet J 36 (4), 356-360 PubMed.
  • Bodo G et al (2004) Autologous osteochondral grafting (mosaic arthroplasty) for treatment of subchondral cystic lesions in the equine stifle and fetlock joints. Vet Surg 33 (6), 588 PubMed.
  • Hanson J A, Seeherman H J, Kirker-Head C A & O'Callaghan M W (1996) The role of computed tomography in evaluation of subchondral osseous lesions in seven horses with chronic synovitis. Equine Vet J 28 (6), 480-488 PubMed.

Other sources of information

  • Ross M W & Dyson S J (2003) Eds Diagnosis and Management of Lameness in the Horse. Elsevier Science, USA.
  • Nixon A J (2003) Update on Management of Subchondral Bone Cysts. In: Proc ACVS Conference 2003.