Reprinted in the IVIS website with the permission of AAEP Close window to return to IVIS IN DEPTH: ULTRASONOGRAPHY OF JOINTS Ultrasonographic Examination of Joints in Horses J.-M. Denoix, DVM, PhD, Agre´ge´; F. Audigie´, DVM, PhD The diagnosis of lesions can be made with ultrasonography in many painful joints with no abnormal radiographic findings. These lesions include ligament, capsule, synovial, and meniscal injuries as well as periarticular injuries. When abnormal radiographic findings are present, complementary ultrasonographic evaluation provides more information concerning the soft tissues and joint surfaces; therefore, a more complete assessment of the joint is achieved. In every clinical case, the ability to diagnose injuries and the reliability of the diagnosis are largely improved when two symmetrical areas are examined; therefore, the homologoid joints of both limbs should always be examined. A systematic approach to every aspect of each joint is necessary to avoid false negative diagnosis. Au- thors’ address: CIRALE–IPC, Ecole Nationale Ve´te´rinaire d’Alfort, Goustranville RN 175, 14 430 Dozule´, France. © 2001 AAEP. 1. Introduction 2. Anatomical Basis Ultrasonography has become an essential procedure for diagnosing joint injuries.1–5 With this tech- Distal Interphalangeal Joint (DIPJ) nique and the new equipment available, noninva- This joint presents five ligaments that can be imaged sive assessment of most of the soft tissues of every ultrasonographically (Figs. 1 and 2): two short and joint in the limbs, back, and pelvis is possible. Ul- long collateral ligaments between the middle phalanx trasonography also provides useful information for (P2) and the distal phalanx (P3), two long and oblique many lesions of the articular surfaces. collateral sesamoidean ligaments between the distal The objectives of this presentation are to de- sesamoid bone (DSB) and P2 as well as the proximal scribe the most interesting anatomical structures phalanx (P1), and a short and wide distal impar sesa- that are frequently injured or that present clinical moidean ligament between the DSB and P3. applications in the field of diagnostic ultrasonog- The DIPJ presents two main recesses that are raphy; to provide reference anatomical figures to accessible with ultrasonography: a dorsal recess aid in the identification of the most important between the dorsal digital extensor tendon and P2 anatomical structures seen during ultrasono- and a proximopalmar recess located proximal to the graphic examination of joints; and to present DSB. The dorsal articular margins of P2 and the the main ultrasonographic abnormal findings of extensor process of P3 can be seen with a dorsal the different joint structures, which will allow the approach to the joint. With a palmaroproximal ap- diagnosis and documentation of many joint proach, the palmar margin of P2 and the proximal conditions. border of the DSB can be imaged. NOTES 366 2001 ր Vol. 47 ր AAEP PROCEEDINGS Proceedings of the Annual Convention of the AAEP 2001 Reprinted in the IVIS website with the permission of AAEP Close window to return to IVIS IN DEPTH: ULTRASONOGRAPHY OF JOINTS limb. The distal aspect of this articular surface can be examined on the flexed fetlock. The articular cartilage is thicker dorsally (ϳ1 mm) than it is dis- tally (ϳ0.5 mm). Shoulder Joint The scapulohumeral joint is closed by a thin articu- lar capsule and does not present any ligament (Fig. 5). This capsule is better seen with lateral and caudolateral approaches than it is with a cranial approach to the joint. It is covered by the supraspi- natus, infraspinatus, and deltoid muscles (Figs. 5 and 6). There is very little synovial fluid in the articular cavity in sound joints. When present, this fluid is seen on a caudolateral approach below the margin of the humeral head. The articular margins are also more easily imaged with lateral and caudolateral approaches: the glenoid cavity has a sharp articu- lar margin on longitudinal sections whereas the hu- meral head has very smooth caudolateral articular margins. The articular surface of the scapula cannot be imaged ultrasonographically. The lateral and cau- dal parts of the humeral head are the only articular surfaces accessible with this technique. The ex- posed surface can be expended when the limb is protracted and adducted. Hock Joint The crurotarsal joint has two strong and complex collateral ligaments (CL). Each of them presents a long and single CL as well as a short CL (Figs. 7–9) Fig. 1. Dissected specimen showing the dorsal aspect of the with a calcanean and a talean part. The talean interphalangeal joints. The two collateral ligaments of the dis- part of the medial CL is divided into superficial and tal interphalangeal joint are symmetrically placed on the dorso- deep fasciculi. These different ligaments do not lateral and dorsomedial aspects of the joint. Middle phalanx (1), have the same orientation (Figs. 8 and 9). There- distal phalanx (2), collateral ligament of the distal interphalan- fore, examination of each of them in longitudinal geal joint (3), collateral ligament of the proximal interphalangeal and transverse sections requires specific orientation joint (4). of the probe. The articular capsule can easily be imaged at the medial and dorsal aspects of the joint. The normal crurotarsal joint has a wide dorsome- Fetlock Joint dial recess that is imaged below the medial malleo- The fetlock joint has a thick dorsal articular capsule lus of the tibia. The normal synovial fluid is totally (Fig. 3). This joint presents two symmetrical anechogenic and the synovial membrane presents collateral ligaments (Fig. 4) with two layers: a distinct villi floating in the synovial fluid. In nor- superficial and long as well as a short and oblique mal horses, there is very little fluid dorsally and layer—except for the suspensory apparatus (third laterally between the talus and the articular capsule interosseus muscle, proximal sesamoid bones and or in the plantarolateral and plantaromedial re- palmar ligament, sesamoidean ligaments). This cesses of the tarsocrural joint. The articular mar- joint presents two main recesses: a dorsal recess gins of the medial malleolus and the medial aspect of with little synovial fluid in normal joints and a fi- the talus are imaged with a medial approach. brous proximodorsal synovial fold, and a proximo- The dorsal aspect of the articular surface of the palmar recess with numerous and high synovial talus is widely exposed, which allows easy imaging villi. of the medial and lateral trochlea ridges of this The dorsal and collateral articular margins are bone. On the flexed hock, the caudoproximal part easily accessible and smooth in normal joints. The of the talus trochlea can also be examined. articular cartilage and subchondral bone surface of The distal tarsus is surrounded by strong liga- the dorsal aspect of the metacarpal (metatarsal) ments made of the distal part of the CL laterally condyle can be imaged on the weight-bearing and medially (Figs. 7–9), the talometatarsal liga- AAEP PROCEEDINGS ր Vol. 47 ր 2001 367 Proceedings of the Annual Convention of the AAEP 2001 Reprinted in the IVIS website with the permission of AAEP Close window to return to IVIS IN DEPTH: ULTRASONOGRAPHY OF JOINTS Fig. 2. Transverse section of the distal interphalangeal joint. The two collateral ligaments of the distal interphalangeal joint are symmetrically placed on the dorsolateral and dorsomedial aspects of the joint. Middle phalanx (1), distal sesamoid bone (2), collateral ligament of the distal interphalangeal joint (3), ungular cartilage (4), proximal aspect of the hoof wall (5). ment dorsally, and the distal plantar ligament cau- The distal articular margin of the patella is dally. Very little synovial fluid can be seen at the smooth. The articular surface of the femoral medial aspect of the distal intertarsal joint or at trochlea is widely exposed on the weight-bearing the plantarolateral aspect of the tarsometatarsal limb. The medial trochlea ridge is thick and pre- joint. The articular margins of these two joints are sents thin articular cartilage (1–2 mm thick), the regular and sharp; the joint spaces with the articu- lateral trochlea ridge is sharp and covered by thick lar cartilage are imaged as an anechogenic gap in articular cartilage (2–4 mm thick), and the femoral the hyperechogenic profile of the distal tarsal bones. trochlea groove often presents an irregular subchon- Stifle Joint dral bone surface. The femorotibial joints present two menisci (Figs. The three patellar ligaments (PL) of the femoropa- 11 and 12), the body and horns of which can be tellar joint (Fig. 10) can be imaged on the longitudi- examined on the weight-bearing limb. On longitu- nal and transverses sections. On transverse sections, the medial PL is triangular, the interme- dinal section, the medial meniscus presents a trian- diate PL is round, and the lateral PL is flat and wide gular radial section with a concave proximal border and is molted over the lateral ridge of the femoral molted over the medial femoral condyle. The body trochlea in its proximal part (Fig. 10). The distal of the lateral meniscus has a trapezoidal shape but part of these ligaments is extra-articular because its cranial and caudal horns have a triangular radial the infrapatellar fat pad is between them and the section. The cranial attachment of each meniscus synovial membrane. can be imaged on longitudinal and transverse sec- On sound stifles, the femoropatellar joints present tions on the flexed limb (Fig. 12). The medial col- two recesses with synovial fluid: one medial, cau- lateral ligament is attached to the medial meniscus dal to the medial PL, and one lateral, caudal to the (Fig. 10) whereas the lateral collateral ligament is lateral PL. High and thick synovial villi are separated from the lateral meniscus by the proximal present in the medial femoropatellar recess. tendon of the popliteus muscle (Fig.