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How to Interpret Radiographs of the Carpus andTarsus of the Young Performance Horse

Elizabeth M. Santschi, DVM, Diplomate ACVS

Author’s address: Department of Veterinary Clinical Sciences, The Ohio State University, 601Vernon L. Tharp Street, Columbus, OH 43210; [email protected]. © 2013 AAEP.

1. Introduction

Routine radiographic evaluation of young perfor-mance horses has become commonplace in Thor-oughbreds but also occurs in other performancebreeds. This practice has resulted in the frequentdiscovery of radiographic abnormalities (RA) thatare often clinically silent but can cause concern inbuyers and sellers of young performance stock.The prevalence of radiographic developmental or-thopedic disease in 6-month-old horses has been re-ported to be 25% in Warmbloods, 41% inStandardbreds, and 34% in Thoroughbreds.1 InThoroughbred yearlings intended for racing, 86.3%exhibit RA2; in young Standardbreds, 42%3; in year-ling Warmblood horses, 69.5%4; and in 1- and2-year-old Quarter Horses intended for cutting,89%.5 Predicting the significance of RA to futureperformance can be challenging and frustrating forbuyers and sellers, which is further complicated bythe possibility of treatment, including surgery, onprognosis.

2. Identifying RA

Because radiographic images are reviewed in sets ofprojections of one joint, this paper will discuss ab-normalities by each projection. Examiners are re-sponsible for reading the entire image; however,

there are areas that are more commonly affected byRA, and they should receive the closest scrutiny.These will be denoted by black circles on the radio-graphic images included in these proceedings. RAbest detected on a specific projection will be listed inbold, but should be confirmed on other projectionswhen possible. Finally, readers should always con-sider three general factors when reviewing radio-graphic images:

(1) Make sure that the films are of the correcthorse.

(2) Make sure the date is appropriate andconsistent.

(3) Make sure all required views are present andof acceptable quality.

3. Carpus

Most radiographic abnormalities in the carpus ofyoung horses can be imaged on three projections:dorsolateral (35°) to palmaromedial oblique, dorso-medial (25°) to palmarolateral oblique, and flexedlateral to medial. A skyline of the distal row canadd information if injury to the dorsal surface of thecarpal bones is suspected. At Thoroughbred sales,this view is used only for horses that have raced andis not routine for younger stock. Traditional de-scriptions of carpal views also include a dorsopalmar

AAEP PROCEEDINGS � Vol. 59 � 2013 379

HOW TO TAKE AND INTERPRET RADIOGRAPHS OF THE YOUNG PERFORMANCE HORSE

NOTES

and standing lateral projection, but, in the interestof controlling cost and radiation exposure, are notincluded in sale radiographs.

Dorsolateral (35°) to Palmaromedial ObliqueProjection of the Carpus (Fig. 1).The areas of greatest concern on this view arethe dorsomedial aspect of the distal radius and theproximal radial, distal radial, and proximal thirdcarpal bones. The radial articulation of the acces-sory carpal bone, the palmar aspect of the ulnarcarpal bone, and the palmar pouch of the middlecarpal joint are also of interest.

Abnormalities best identified on the dorsolateral(35°) to palmaromedial oblique are listed below. Ifthe RA is in bold type, it is the best projection todetect that RA.

(1) Osteochondral fragments or remodelingof the distal radial carpal bone

(2) Osteochondral fragments or remodelingof the proximal third carpal bone

(3) Osteochondral fragments or remodelingof the distomedial radius

(4) Osteochondral fragments or remodeling of theproximal radial carpal bone

(5) Fractures of the radial articulation of the ac-cessory carpal bone

(6) Palmar fragments in the middle carpal joint(7) Ulnar carpal bone lucencies or axial fragments

Dorsomedial (25°) to Palmarolateral ObliqueProjection of the Carpus (Fig. 2).The areas of greatest concern on this view arethe dorsolateral aspect of the distal radius and theproximal intermediate, distal intermediate, andproximal third carpal bones. The ulnar carpal boneand the palmar pouch of the middle carpal joint arealso of interest.

Abnormalities best projected on the dorsomedial(25°) to palmarolateral oblique projection of the car-pus are listed below. If the RA is in bold type, it isthe best projection to detect that RA.

Fig. 1. Carpus dorsolateral (35°) to palmaromedial oblique pro-jection. This image demonstrates remodeling of the distal radialand proximal third carpal bones (white circle). This radiographwill be discussed by the panel as Case 1.

Case Prognosis Summary

Case 1. Remodeling of the Distal Radial and Proximal Third CarpalBones

PerformanceGoal

SurgeryYes/No/Maybe

ExcellentPrognosis

GoodPrognosis

GuardedPrognosis

PoorPrognosis

Racing Yesowner/buyer

Westernperformance Yes

owner/buyer

Englishperformance Yes

owner/buyer

Generalpurpose Yes owner buyer


Case 2. Remodeling of the Distal Intermediate Carpal Bone

PerformanceGoal

SurgeryYes/No/Maybe

ExcellentPrognosis

GoodPrognosis

GuardedPrognosis

PoorPrognosis

Racing Noowner/buyer

Westernperformance No

owner/buyer

Englishperformance No

owner/buyer

Generalpurpose No

owner/buyer

Fig. 2. Carpus dorsomedial (25°) to palmarolateral oblique pro-jection. This image demonstrates remodeling of the distal inter-mediate carpal bone (white circle). This radiograph will bediscussed by the panel as Case 2.

380 2013 � Vol. 59 � AAEP PROCEEDINGS


(1) Osteophytes on the proximal intermedi-ate carpal bone

(2) Osteophytes or remodeling on the distalintermediate carpal bone

(3) Osteochondral fragments from the disto-central radius or proximal intermediate car-pal bone

(4) Osteochondral fragments from the prox-imal third carpal bone

(5) Osteochondral fragments from the plamar as-pect of the radial carpal bone

Flexed Lateral to Medial Projection of theCarpus (Fig. 3).The areas of greatest concern on this view arethe proximal dorsal margin of the radial and inter-mediate carpal bones, the distal dorsal margin of theradial and intermediate carpal bones, the proximaldorsal margin of the third carpal bone, and the cau-dal aspect of the distal radius.

Abnormalities best projected on the flexed lateralto medial projection of the carpus are listed be-

low. If the RA is in bold type, it is the best projec-tion to detect that RA.

(1) Osteochondral fragments or remodelingof the distal radial carpal bone

(2) Osteochondral fragments or remodelingof the distal intermediate carpal bone

(3) Osteochondral fragments or remodelingof the proximal third carpal bone

(4) Osteochondroma formation on the cau-dal radius

Carpal abnormalities that are believed to affectlater athletic performance are not common and aregenerally reported to have a �7% prevalence insales yearlings (Table 1). Lucencies in the ulnarcarpal bone are detected with greater frequency butare generally considered insignificant blemishes.

Fig. 3. Carpal flexed lateral to medial projection. This imagedemonstrates a small osteochondroma on the caudal radius(white circle). This radiograph will be discussed by the panel asCase 3. Fig. 4. Tarsal dorsomedial (65°) to plantarolateral oblique pro-

jection. This image demonstrates a DIRT lesion composed ofmultiple fragments (white circle). This radiograph will be dis-cussed by the panel as Case 4.


Case 3. Small Osteochondroma on the Caudal Distal Radius

PerformanceGoal

SurgeryYes/No/Maybe

ExcellentPrognosis

GoodPrognosis

GuardedPrognosis

PoorPrognosis



owner/buyer


owner/buyer

Generalpurpose No

owner/buyer


Case 4. DIRT Lesion With Multiple Fragments

PerformanceGoal

SurgeryYes/No/Maybe

ExcellentPrognosis

GoodPrognosis

GuardedPrognosis

PoorPrognosis



owner/buyer


owner/buyer

Generalpurpose Maybe

owner/buyer



4. Tarsus

Similar to the carpus, most radiographic abnormal-ities of the tarsus of young horses can be imaged on

three projections: dorsomedial (65°) to plantarolat-eral oblique, dorsolateral (10°) to plantaromedial,and lateral to medial. Traditional descriptions oftarsal views include a lateral to medial oblique pro-

Fig. 5. Tarsal dorsolateral (10°) to plantaromedial projec-tion. This image demonstrates mild tarsocrural effusion (whitearrows) and a large medial malleolar lucency with fragments (whitecircle). This radiograph will be discussed by the panel as Case 5.

Fig. 6. Tarsal lateral to medial projection. This image demon-strates a large enthesophyte on MT3 at the dorsal margin of thetarso-metatarsal joint and another on the distal aspect of themedial trochlear ridge (white circle). This radiograph will bediscussed by the panel as Case 6.

Table 1. Prevalence of Carpal Radiographic Abnormalities in Young Performance Horses

Carpal Radiographic Abnormality Breed Prevalence Reference

Fragment Thoroughbred 0.7–2.2% 2, 5, 8Osteophytes Thoroughbred 1.1–3.3% 2, 6–8Osteophytes Quarter Horse 3.5% 9Enthesophyte Thoroughbred 2.6% 2Ulnar carpal bone lucency Thoroughbred 8.3–22.2% 2, 6, 7Dorsomedial carpal disease Thoroughbred 2.7% 6Dorsomedial carpal disease Quarter Horse 6.4% 9Subchondral cyst Thoroughbred 0.2–0.3% 6, 8Accessory carpal bone fracture Thoroughbred 0.40% 6


Case 5. Large Medial Malleolar Lucency With Multiple Fragments

PerformanceGoal

SurgeryYes/No/Maybe

ExcellentPrognosis

GoodPrognosis

GuardedPrognosis

PoorPrognosis



owner/buyer


owner/buyer

Generalpurpose Yes

owner/buyer


Case 6. Two Enthesophytes: Dorsal Margin of MT3 at the Tarsometa-tarsal Joint and Distal Aspect of the Medial Trochlear Ridge

PerformanceGoal

SurgeryYes/No/Maybe

ExcellentPrognosis

GoodPrognosis

GuardedPrognosis

PoorPrognosis



owner/buyer


owner/buyer

Generalpurpose No

owner/buyer



Table 2. Prevalence of Tarsal Radiographic Abnormalities in Young Performance Horses

Tarsal Radiographic Abnormality Breed Prevalence Reference

Any Warmbloods 31.4% 4Any Quarter Horse 68.2% 9OCD of DIRT Thoroughbred 3.4–5% 2, 5, 7, 8OCD of DIRT Quarter Horse 3.8% 2, 6–8OCD of DIRT Standardbred 14.5–17.7% 10, 11OCD of medial malloleus of tibia Thoroughbred 0.4–1.8% 2, 5–8OCD of medial malloleus of tibia Quarter Horse 1.10% 9OCD of medial malloleus of tibia Standardbred 2.5% 10, 11OCD of lateral malloleus of tibia Thoroughbred 0.5% 2OCD medial trochlear ridge of talus Thoroughbred 0.1–2.4% 2, 5, 7, 8OCD medial trochlear ridge of talus Quarter Horse 0.8% 9OCD lateral trochlear ridge of talus Thoroughbred 1–2.6% 2, 5, 7, 8OCD lateral trochlear ridge of talus Quarter Horse 2.3% 9OCD lateral trochlear ridge of talus Standardbred 1.6–3.8% 10, 11Dorsal osteophytes PIT, DIT, TMT Thoroughbred 20.1–25% 2, 5, 7, 8Dorsal osteophytes PIT, DIT, TMT Quarter Horse 47.9% 9Fractures Thoroughbred 0.1% 2Lucency DIT, TMT Thoroughbred 7.30% 5Wedging of T3 or T central Thoroughbred 0.6–1.6% 5–7Wedging of T3 or T central Quarter Horse 6.9% 9

OCD indicates osteochondrosis; DIRT, distal intermediate ridge of talus; PIT, proximal intertarsal joint; DIT, distal intertarsal joint;TMT, tarsometatarsal joint; T3, third tarsal bone; T central, central tarsal bone.

Case Prognosis SummaryCase 7. Small DIRT Fragment and Large Distal Lateral Trochlear RidgeFragment

PerformanceGoal

SurgeryYes/No/Maybe

ExcellentPrognosis

GoodPrognosis

GuardedPrognosis

PoorPrognosis



owner/buyer


owner/buyer

Generalpurpose Yes

owner/buyer

Case Prognosis SummaryCase 8. Remodeling of the Dorsal Margins of the Central and ThirdTarsal Bones and Proximal MT3

PerformanceGoal

SurgeryYes/No/Maybe

ExcellentPrognosis

GoodPrognosis

GuardedPrognosis

PoorPrognosis



owner/buyer


owner/buyer

Generalpurpose No

owner/buyer

Case 7. Small DIRT fragment and large distal lateral trochlearridge fragment.

Case 8. Remodeling of the dorsal margins of the central andthird tarsal bones and proximal MT3.



jection, but, in young horses, this is of minimal ad-ditional benefit.

Dorsomedial (65°) to Plantarolateral ObliqueProjection of the Tarsus (Fig. 4).The areas of greatest concern on this view arethe distal intermediate ridge of the tibia (DIRT), thelateral trochlear ridge of the talus, and the dorsolat-eral margin of the proximal and distal intertarsaland tarsometatarsal joints.

Abnormalities best projected on dorsomedial (65°)to plantarolateral oblique projection of the tarsusare listed below. If the RA is in bold type, it is thebest projection to detect that RA.

(1) Osteochondral fragments on the distalintermediate ridge of the tibia

(2) Defects and osteochondral fragments ofthe lateral trochlear ridge of the talus

(3) Osteoarthritis and fractures of the central andthird tarsal bones

Dorsomedial (10°) to PlantarolateralProjection of the Tarsus (Fig. 5).The areas of greatest concern on this view is themedial malleolus. However, tarsocrural effusion

can also be best detected on this view, which canincrease scrutiny of other typical locations of abnor-malities, and, rarely, bony injury to the proximalmetatarsus can be detected.

Abnormalities best projected on the dorsolateral(10°) to plantaromedial projection view of the tarsusare listed below. If the RA is in bold type, it is thebest projection to detect that RA.

(1) Lucencies and osteochondral fragmentson the axial aspect of the medial malleolus

(2) Tarsocrural effusion(3) Plantar damage on MT3 at suspensory origin

Lateral to Medial Projection of the Tarsus(Fig. 6).The areas of greatest concern on this view are thedistodorsal tibia, the dorsal aspect of both trochlearridges, and the dorsal aspect of the proximal and distalintertarsal and the tarsometatarsal joints.


Case 9. Ulnar Carpal Bone Lucency With Fragment

PerformanceGoal

SurgeryYes/No/Maybe

ExcellentPrognosis

GoodPrognosis

GuardedPrognosis

PoorPrognosis



owner/buyer


owner/buyer

Generalpurpose No

owner/buyer


Case 10. Remodeling of the Distal Radial Carpal Bone

PerformanceGoal

SurgeryYes/No/Maybe

ExcellentPrognosis

GoodPrognosis

GuardedPrognosis

PoorPrognosis

Racing Maybe owner buyerWestern

performance Noowner/buyer


owner/buyer

Generalpurpose No

owner/buyer

Case 10. Remodeling of the distal radial carpal bone.

Case 9. Ulnar carpal bone lucency with fragment.



Abnormalities best projected on the lateral to me-dial projection of the tarsus are listed below. If theRA is in bold type, it is the best projection to detectthat RA.

(1) Degenerative joint disease of the distalintertarsal and tarsometatarsal joints

(2) Small axial DIRT fragments(3) Enthesophytes of proximodorsal MT3(4) Osteochondral fragments in the proximal in-

tertarsal jointTarsal abnormalities that are believed to affect

later athletic performance are fairly common (31–68%) and the frequency appears to vary by breed(Table 2).6–11

5. Determining the Significance of an RA toPerformance

Some studies of young stock have included RA of thecarpus and tarsus in their attempts to associateyoung horse RA and performance.2,12 These stud-ies can be challenging to interpret by strict statisti-cal methods (P � 0.05) because they have manyconfounding factors and incomplete outcome infor-mation, usually racing data only. Because of theoverall low numbers of affected horses, subclassify-ing lesions (size, severity, number of limbs affected,etc) to determine prognosis is usually not possible.However, these studies do have important informa-tion to help guide veterinarians examining youngperformance horses. RA in the carpus or tarsusthat have been associated with poorer racing out-comes (P � 0.05) include dorsal medial intercarpaljoint disease and osteophytes in distal intertarsal ortarsometatarsal joints.12 RA in the tarsus or car-pus that demonstrate a tendency (P � 0.2) for poorerracing performance include carpal osteophytes,fracture of accessory carpal bone, change of medialtrochlear ridge of talus,12 and osteochondrosis ofDIRT or medial malleolus.2

There also are multiple publications that focus onthe treatment of a specific carpal or tarsal lesion,and some of these studies have been able to gradelesions and document that severity or size can affectprognosis.13–17 Clinicians must judge young stockwith RA on the basis of careful reading of availablestudies, experience with RA in a given performancediscipline, and evaluation of the appearance andclinical presentation of a specific RA.

6. Prognosis for Carpal or Tarsal RA After Treatment

● Arthroscopy for osteochondral chip fractures ofcarpus: 68% race at level equal to or betterthan previous, 11% at lower level; greater car-tilage damage results in lower success.13

● Arthroscopy for lucency of third carpal bone(Standardbreds); 75% race at equal level, 14%at lower.14

● Arthroscopy for lucency of distal radial carpalbone; 68% race at level equal to or better thanprevious, 12% at lower.15

● Arthroscopy for tarsocrural osteochondrosis(Standardbreds); 75% race after surgery.16

● Arthroscopy for tarsocrural osteochondrosis(Standardbreds);43% race at 3 years of ageafter surgery; Thoroughbreds, 78% race at 3years of age.17

7. Cases

The summary prognosis charts (1–10) with each im-age are predicated on the lesion being detected in ayearling intended for one of the four disciplines.The focus is on performance and not resale blem-ishes. The prognosis given to a horse owner andthe prognosis given to a potential buyer, if different,is indicated.References1. Lepeule J, Bareille N, Valette JP, et al. Developmental ortho-

paedic disease in the limbs of foals: between-breed variations inthe prevalence, location and severity at weaning. Animal 2008;2:284–291.

2. Jackson M, Vizard A, Anderson G, et al. A Prospective Study ofPresale Radiographs of Thoroughbred Yearlings. Australian Gov-ernment Rural Industries Research and Development Corpora-tion. RIRDC Publication No. 09/082. https://rirdc.infoservices.com.au/downloads/09–082.pdf. 2009.

3. Courourse-Malblanc A, Leleu C, Bouchilloux M, et al. Abnormalradiographic findings in 865 French Standardbred trotters andtheir relationship to racing performance. Equine Vet J Suppl2006;36:417–422.

4. van Grevenhof EM, Ducro BJ, van Weeren PR, et al. Prevalenceof various radiographic manifestations of osteochondrosis andtheir correlations between and within joints of Dutch Warmbloodhorses, Equine Vet J 2009;41:11–16.

5. Kane AJ, McIlwraith CW, Park RD, et al. Radiographic changesin Thoroughbred yearlings, part 1: prevalence at the time of theyearling sales. Equine Vet J 2003;35:354–365.

6. Furniss C, Carstens A, van den Berg SS. Radiographic changesin Thoroughbred yearlings in J South African Vet Assoc 2011;82:194–204.

7. Scott NJ, Hance S, Todhunter P, et al. Incidence of radiographicchanges in Thoroughbred yearlings: 755 cases. Adv Equine Nu-trition III 2005;347–348.

8. Oliver LJ, Baird DK, Baird AN, et al. Prevalence and distribu-tion of radiographically evident lesions on repository films I thehock and stifle joints of yearling Thoroughbred horses in NewZealand. N Z Vet J 2008;56:202–209.

9. Contino EK, Park RD, McIlwraith CW. Prevalence of radio-graphic changes in yearling and 2-year-old Quarter Horses in-tended for cutting. Equine Vet J 2012;44:185–195.

10. Alvarado A, Marcoux M, Breton L. The incidence of osteochon-drosis in a Standardbred farm in Quebec, in Proceedings. AmAssoc Equine Pract 1989;35:293–307.

11. Lykkjen S, Roed KH, Dolvik NI. Osteochondrosis and osteochon-dral fragments in Standardbred trotters: prevalence and rela-tionships. Equine Vet J 2012;44:332–338.

12. Kane AJ, McIlwraith CW, Park RD, et al. Radiographic changesin Thoroughbred yearlings, part 2: associations with racing per-formance. Equine Vet J 2003;35:366–374.

13. McIlwraith CW, Yovich JV, Martin GS. Arthroscopic surgery forthe treatment of osteochondral chip fractures in the equine car-pus. J Am Vet Med Assoc 1987;191:531–540.

14. Ross MW, Richardson DW, Beroza GA. Subchondral lucency of thethird carpal bone in Standardbred racehorses: 13 cases (1982–1988)J Am Vet Med Assoc 1989;195:789–794.

15. Dabreiner RM, White NA, Sullins KE. Radiographic and ar-throscopic findings associated with subchondral lucency of the distalradial carpal bone in 71 horses. Equine Vet J 1996;28:93–97.

16. Laws EG, Richardson DW, Ross MW, et al. Racing performanceof Standardbreds after conservative and surgical treatment fortarsocrural osteochondrosis. Equine Vet J 1993;25:199–202.

17. Beard WL, Bramlage LR, Schneider RK, et al. Postoperative rac-ing performance in Standardbreds and Thoroughbreds with osteo-chondrosis of the tarsocrural joint: 109 cases (1984–1990). J AmVet Med Assoc 1994;204:1655–1659.



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