Biceps femoris muscle transposition for treatment of cranial cruciate ligament rupture in small breed dogs

The purpose of this study was to evaluate a new extracapsular surgical technique for the treatment of cranial cruciate ligament rupture in small breed dogs. Nine small breed dogs (seven females and two males) weighing ≤ 15 kg were treated with biceps femoris muscle transposition (BFT). The duration of the BFT procedure was 20 min. Each patient underwent a standard clinical protocol and a questionnaire for the owners. Follow-up (at 1, 3, and 12 months postoperative) confirmed significant improvement in all patients, especially at 1 month postoperatively (p < 0.01) and again after complete stifle joint assessment at 3 months postoperatively. After 12 months, only two patients showed a slight increase in osteoarthritis. According to our results, BFT is a simple extracapsular surgical technique that can be used for the treatment of cranial cruciate ligament rupture in small breed dogs.     

Evaluation of partial cranial cruciate ligament rupture with positive contrast computed tomographic arthrography in dogs

Computed tomographic arthrography (CTA) of four cadaveric canine stifles was performed before and after partial cranial cruciate ligament rupture in order to verify the usefulness of CTA examination for the diagnosis of partial cranial cruciate ligament rupture. To obtain the sequential true transverse image of a cranial cruciate ligament, the computed tomography gantry was angled such that the scanning plane was parallel to the fibula. True transverse images of cranial cruciate ligaments were identified on every sequential image, beginning just proximal to the origin of the cranial cruciate ligament distal to the tibial attachment, after the administration of iodinated contrast medium. A significant decrease in the area of the cranial cruciate ligament was identified on CTA imaging after partial surgical rupture of the cranial cruciate ligament. This finding implies that CTA can be used for assessing partial cranial cruciate ligament ruptures in dogs.     

Long-term radiographic comparison of tibial plateau leveling osteotomy versus extracapsular stabilization for cranial cruciate ligament rupture in the dog

OBJECTIVE: Comparison of 2 methods of surgical management of cranial cruciate ligament (CCL) injury in large-breed dogs using a radiographic osteoarthrosis (OA) scoring system. STUDY DESIGN: Retrospective study. ANIMALS: Client-owned dogs (n=66). METHODS: Radiographs were evaluated from dogs weighing >/=22.7 kg, with surgical management of CCL rupture using extracapsular repair (ECR) or tibial plateau leveling osteotomy (TPLO). Radiographs were taken immediately before surgery and >/=12 months later. An OA score was assigned to each set of radiographs taken at the preoperative and final examinations by evaluating 32 specific features of stifle OA. The difference between preoperative and final OA scores were subtracted and 2 final score categories of a change 5 were created. A logistic regression model was used to evaluate the effect of right versus left pelvic limb, age, preoperative weight, postoperative weight, days from surgery until final radiographic recheck, cranial cruciate status at surgery, medial meniscus status at surgery, and ECR versus TPLO. RESULTS: The ECR group had 27 stifles (22 dogs) and the TPLO group had 52 stifles (44 dogs). ECR dogs had a preoperative weight of 33.4+/-9.3 kg (range 22.7-54.1 kg) and a preoperative OA score of 13.0+/-8.4 (range 1-34) compared with TPLO dogs that had a preoperative weight of 38.9+/-9.1 kg (range 25-63.9 kg) and preoperative OA score of 15.9+/-8.4 (range 4-44). Postoperative weights for ECR and TPLO dogs were 33.6+/-9 kg (range 21.8-54.6 kg) and 39.4+/-10.1 kg (range 24-72 kg), respectively. Final OA scores were: ECR dogs, 26.3+/-10.8 (range, 10-54); TPLO dogs, 23.3+/-9.5 (range, 12-50). Dogs with a final change in OA score of >/=6 were 5.78 times more likely to have had ECR compared with those that had TPLO as stabilization procedure (odds ratio=5.78; Log-likelihood test P-value=.025). Other dependent variables were not significant. CONCLUSIONS: Based on logistic regression analysis, dogs with larger OA score differences were 5.78 times more likely to have had ECR than TPLO. CLINICAL RELEVANCE: Prospective, randomized surgical trials with pre-defined objective measures would be required to further evaluate the clinical importance of these preliminary findings which suggest that TPLO may help stabilize the cranial tibial thrust as originally proposed.     

Localization of cathepsin K and tartrate-resistant acid phosphatase in synovium and cranial cruciate ligament in dogs with cruciate disease

OBJECTIVE: To localize cathepsin K and tartrate-resistant acid phosphatase (TRAP) in synovium and cranial cruciate ligament (CCL) of dogs with cruciate disease. ANIMALS: Dogs (n=15) with cruciate disease and ruptured CCL, and 12 dogs with intact CCL. METHODS: Synovium and CCL were examined histologically and cells containing cathepsin K or TRAP were identified immunohistochemically and histochemically, respectively. RESULTS: Increased cellular localization of cathepsin K and TRAP was detected in synovium and ruptured CCL in dogs with cruciate disease, when compared with tissues from dogs with intact CCL. Inflammation of synovium with TRAP+ macrophage-like cells was seen in 73% of dogs with CCL disease, but was not seen in dogs with intact CCL. The presence of cathepsin K and TRAP protein in synovium and CCL tissues was significantly correlated in dogs with CCL rupture. CONCLUSION: Inflammation of the epiligament of ruptured CCL with cathepsin K+ and TRAP+ macrophage-like cells forms part of a similar, more generalized chronic inflammatory change within the periarticular tissues of the stifle of a large proportion of dogs with CCL rupture. CLINICAL RELEVANCE: Production of matrix-degrading enzymes by the synovium may induce progressive pathologic rupture of the CCL. Therefore, these collagenolytic pathways may offer a novel target for medical therapy of joint inflammation in canine patients with cruciate disease.     

Stifle joint osteoarthritis at the time of diagnosis of cranial cruciate ligament injury is higher in Boxers and in dogs weighing more than 35 kilograms

Osteoarthritis is a ubiquitous disease in dogs. The purpose of this retrospective study was to characterize the severity and distribution of osteoarthritis (OA) within the joint and to identify differences among dog breeds in the severity of OA in the cranial cruciate ligament (CCL)‐deficient stifle joint. Radiographs of 240 stifles from 51 Boxers, 66 German Shepherds, 100 Labrador Retrievers, and 23 Siberian Huskies with confirmed CCL rupture were included. Radiographs of the stifle joint were evaluated and OA severity was graded at 33 sites within and around the joint, and patella alta was graded as present or absent for a potential total stifle OA score of 100. Osteophyte size was correlated to OA severity score. Total OA scores were calculated and compared within and between breeds globally as well as at each joint site. Dogs weighing >35 kg had a higher total OA score than those weighing <35 kg. Osteoarthritis scores were highest at the apical patella, proximolateral tibia, and sesamoid bones, corresponding to the proximal, lateral, and caudal aspects of the joint, respectively. No statistically significant differences were found among the mean OA scores of various stifle joint regions. Boxer dogs had a higher total OA score than other breeds. We concluded that dogs have a consistent distribution pattern of OA within the stifle joint after CCL injury. Radiographic OA is more severe in the proximal, lateral, and caudal aspects of the joint. Boxers had more severe OA than the other breeds evaluated in the study.     

Degenerative changes of the cranial cruciate ligament harvested from dogs with cranial cruciate ligament rupture

Degenerative cranial cruciate ligament (CCL) rupture is characterized histologically by degenerating extracellular matrix (ECM) and chondroid metaplasia. Here, we describe the progression of chondroid metaplasia and the changes in the expression of ECM components in canine CCL rupture (CCLR). CCLs from 26 stifle joints with CCLR (CCLR group) and normal CCLs from 12 young beagles (control group) were examined histologically and immunohistochemically for expression of type I (COLI), type II (COLII), type III collagen (COLIII) and Sry-type HMG box 9 (SOX9). Cell density and morphology of CCLs were quantified using hematoxylin–eosin staining. The percentage of round cells was higher in the CCLR group than in controls. COLI-positive areas were seen extensively in the connecting fibers, but weakly represented in the cytoplasm of normal CCLs. In the CCLR group, there were fewer COLI-positive areas, but many COLI-positive cells. The percentages of COLII-, COLIII- and SOX9-positive cells were higher in the CCLR group than in controls. The number of spindle cells with perinuclear halo was high in the CCLR group, and most of these cells were SOX9-positive. Deposition of COLI, the main ECM component of ligaments, decreased with increased COLIII expression in degenerated CCL tissue, which shows that the deposition of the ECM is changed in CCLR. On the contrary, expression of SOX9 increased, which may contribute to the synthesis of cartilage matrix. The expression of COLII and SOX9 in ligamentocytes showed that these cells tend to differentiate into chondrocytes.     

Applications of evidence-based medicine: cranial cruciate ligament injury repair in the dog

OBJECTIVE: To evaluate the literature reporting surgical interventions pertaining to canine cranial cruciate ligament (CCL) injury using an evidence-based medicine paradigm. STUDY DESIGN: Systematic literature review. METHODS: An on-line bibliographic search through Medline, PubMed, Veterinary Information Network, and Commonwealth Agricultural Bureau Abstracts was performed during August 2004. Two hundred and forty resources of information were identified. Studies were compared and evaluated with regard to study design (retrospective, prospective, randomization), surgical technique, short- and long-term follow-up, and evidence classification. RESULTS: Twenty-eight resources qualified to assist with evidence classification. No class I or class II studies were present, 5 studies were categorized as a class III and 23 studies were categorized as a class IV. Seventeen studies were retrospectively designed and 11 studies were prospectively designed. Proposed results ranged from a wide variety of subjective findings including clinical impression, radiographic analysis, synovial fluid analysis, gross pathology, and histopathology. Objective results, although infrequent, included force plate analysis and cadaveric biomechanical testing. CONCLUSIONS: At this time, the application of evidence-based medicine in analyzing the current available evidence suggests that there is not a single surgical procedure that has enough data to recommend that it can consistently return dogs to normal function after CCL injury. The requirement for assessing and categorizing the available evidence becomes increasingly important as more data becomes available and the quality of research improves. CLINICAL RELEVANCE: An evidence-based medicine paradigm did not provide sufficient evidence favoring 1 surgical technique for management of canine CCL injury.     

Accuracy of 3 Tesla magnetic resonance imaging using detection of fiber loss and a visual analog scale for diagnosing partial and complete cranial cruciate ligament ruptures in dogs

Canine cranial cruciate ligament rupture is often bilateral and asymmetrical, ranging from partial to complete rupture. The purpose of our diagnostic accuracy study was to assess the accuracy of 3 Tesla magnetic resonance imaging (MRI) detection of fiber loss and use of a visual analog scale in the diagnosis of complete versus partial cranial cruciate ligament rupture in 28 clinical dogs with unilateral complete rupture and contralateral partial rupture. Three Tesla MRI was performed on 56 stifles using sagittal sequences (T2‐weighted fast spin echo with fat saturation, proton density fast spin echo, and T2‐weighted 3D fast spin echo CUBE). Two MRI observers assessed the cranial cruciate ligament for fiber loss and completed a visual analog scale. The MRI data were compared to arthroscopy and clinical status. Accuracy classifying partial or complete rupture was assessed using receiver operating characteristic analysis. Compared to arthroscopy, for complete cranial cruciate ligament rupture, sensitivity, specificity, and accuracy of MRI detection of fiber loss were 0.78, 0.50–0.60, and 0.68–0.71, respectively, and, for partial tears, specificity was 1.00. An MRI visual analog scale score ≥79 was indicative of complete cranial cruciate ligament rupture (sensitivity 0.72–0.94 and specificity 0.71–0.84). Using a visual analog scale cut‐point ≥79, observers achieved good accuracy discriminating clinical status of partial or complete cranial cruciate ligament rupture (area under the curve 0.87–0.93). MRI evaluation for fiber loss and use of a visual analog scale are specific in stifles with clinically stable partial cranial cruciate ligament rupture. In stifles with clinically unstable complete cranial cruciate ligament rupture, both MRI tests are sensitive though not specific compared to arthroscopy. As a diagnostic imaging method, MRI may help guide treatment in patients with cranial cruciate ligament damage, particularly for stable partial rupture.     

An in vitro study to determine the effectiveness of a patellar ligament/fascia lata graft and new tibial suture anchor points for extracapsular stabilization of the cranial cruciate ligament-deficient stifle in the dog

OBJECTIVE: (1) To determine whether an extracapsular patellar ligament/fascia lata graft would provide stability in the cranial cruciate ligament (CrCL)-deficient stifle comparable with that of the intact stifle. (2) To determine if different tibial anchor points would enhance stability of the CrCLdeficient stifle when compared with the standard fabellar-tibial suture (FTS) placement. STUDY DESIGN: Experimental. ANIMALS: Twenty-eight canine cadaver hind limbs. METHODS: Stifles were mounted in a jig and tested between loads of -65 and 80 N. After testing the intact CrCL, 4 stabilization techniques were tested after CrCL transection: lateral graft technique (LGT) and 3 FTS with different tibial anchor points. RESULTS: There were no significant differences in displacement between the LGT and standard FTS, between the LGT and the intact CrCL, or between the FTS and the intact CrCL, in either the Securos or the Screw-washer experiments. Stiffness of the intact CrCL was significantly greater than that of any stabilization technique and the cut CrCL. The standard FTS showed the least displacement of all suture stabilization techniques. Differences in stiffness were not significant between the suture stabilization techniques. CONCLUSIONS: Securely anchored, the LGT results in a reduction in drawer motion similar to that of the intact CrCL and the standard FTS. Altering the tibial anchor point for the FTS does not improve stiffness or enhance stabilization of the CrCL-deficient stifle. CLINICAL RELEVANCE: The LGT could be used for the treatment of CrCL ruptures in the dog. A clinical study is recommended.     

Proximal tibial intraarticular ostectomy for treatment of canine cranial cruciate ligament injury

OBJECTIVE: To report a technique for surgical alteration of the slope of the tibial plateau by a proximal tibial intraarticular ostectomy (PTIO) after injury to the canine cranial cruciate ligament (CCL) and to determine the outcome. STUDY DESIGN: Prospective clinical study. ANIMALS: Dogs (n=52) with CCL injury in 60 stifle joints. METHODS: CCL injury was treated by lateral stifle arthrotomy, removal of CCL remnants, and appropriate meniscal surgery. PTIO was performed to remove a wedge of bone from the proximal aspect of the tibia. The ostectomy site was reduced and stabilized using a bone plate and screws applied to the medial surface of the tibia as well as a craniocaudal positional screw. Dogs were evaluated at 6 weeks, 6, and 12 months by complication assessment, lameness scores, stifle range of motion (ROM), thigh circumference, radiographic assessment, degenerative joint disease (DJD) scores, and surgeon and owner evaluation of function. RESULTS: Lameness scores improved by 6 and 12 months in all but 1 dog. Thigh circumference and DJD were increased at 6 and 12 months. Complications occurred in 20% of dogs with all but 1 occurring perioperatively or within 6 weeks; most common were injury to the long digital extensor tendon (4 dogs) and plate failure (3); 2 other dogs required surgery to treat complications. Most owners (98%) reported that lameness had improved by 12 months; 90% were extremely or very satisfied with the procedure and 90% would have the same procedure performed on another dog. CONCLUSION: PTIO to level the tibial plateau provided a satisfactory clinical outcome in dogs >20 kg with CCL injury and the complication rate was similar to tibial plateau levelling osteotomy (TPLO). Stifle osteoarthritis continued to progress radiographically. CLINICAL RELEVANCE: PTIO represents an alternative to TPLO that does not require specialized surgical equipment.     

Caudal cruciate ligament damage in dogs with cranial cruciate ligament rupture

Objective: To investigate the incidence of caudal cruciate ligament (CaCL) damage in dogs with cranial cruciate ligament rupture (CCLR). Study Design: Prospective clinical study. Animals: Dogs (n=24) admitted for surgical stabilization of the stifle after CCLR and 8 healthy dogs with intact cranial cruciate ligament (CCL) and CaCL studied as controls. Methods: Preoperative radiographs and stifle joint images (arthrotomy, 6; arthroscopy, 18) were collected from dogs with CCLR. Severity of arthritis, synovitis, CCL damage, and CaCL damage were assessed using numerical rating scales. The CaCL was probed to determine whether minor fraying or a full thickness defect in the ligament was present. Data collected from the study population were compared with the control population of dogs. Results: The CaCL was damaged in 21/24 (88%) of dogs with CCLR; 6/24 (25%) had a full thickness defect in the CaCL. Severity of stifle synovitis and severity of damage to the CaCL were positively correlated (P<.05). Conclusions: The CaCL is damaged in a high percentage of dogs with CCLR. A significant and positive correlation exists between the degree of synovitis present and the extent of CaCL damage. Clinical Relevance: In dogs with CCLR, cruciate ligament pathology typically involves both the CCL and CaCL. As the severity of synovitis and the extent of CaCL damage are related, this observation supports the hypothesis that stifle synovitis may contribute to CCL and CaCL degeneration and subsequent damage.     

Partial rupture of the cranial cruciate ligament in dogs

Four cases of partial rupture of the craniomedial part of the cranial cruciate ligament (CCL) are presented. Clinical examination revealed only subtle signs of CCL injury. The cranial drawer sign was present in two dogs and in flexion only. As the cranial drawer sign is not always evident a tentative diagnosis of partial CCL rupture should be based on history, joint tenderness and joint effusion. Arthrotomy and careful probing of the ligament is indicated. In these cases the lesion was treated immediately after diagnosis to prevent further degeneration and possible total rupture of the ligament. A fascial graft using the ‘over the top’ reconstruction technique was performed leaving the intact portion of the ligament in situ. Follow-up examination after four to six months revealed normal limb function in three dogs whereas slight and periodic lameness persisted in one dog.     

Angle between the patellar ligament and tibial plateau in dogs with partial rupture of the cranial cruciate ligament

OBJECTIVE: To measure the angles between the patellar ligament and the tibial plateau and between the patellar ligament and the common tangent at the tibiofemoral contact point (TFCP) in stifle joints of dogs with partial rupture of the cranial cruciate ligament (CrCL) for comparison with data obtained for stifle joints in dogs with intact CrCLs. SAMPLE POPULATION: 60 stifle joints of 54 dogs with surgically confirmed partial CrCL rupture. PROCEDURES: Mediolateral radiographic views of the stifle joints were obtained, and the angles between the patellar ligament and the conventionally defined tibial plateau (angle gamma) and between the patellar ligament and the common tangent to the TFCP (angle alpha) were measured at incidental stifle joint flexion (angle beta) by 2 independent observers. Data underwent linear regression analysis and were compared with findings in joints of dogs without degenerative joint disease. RESULTS: In stifle joints of dogs with a partial rupture of the CrCL, angles gamma and alpha were 5 degrees and 2 degrees larger than each corresponding angle in healthy canine joints. At 100 degrees of flexion, the patellar ligament was perpendicular to the conventionally defined tibial plateau. At 110 degrees of flexion, the patellar ligament was perpendicular to the common tangent at the TFCP. CONCLUSIONS AND CLINICAL RELEVANCE: In dogs, stifle joints with partially ruptured CrCLs have marginally larger angles between the patellar ligament and the tibial plateau, compared with joints with intact CrCLs; at equivalent angles of flexion, comparatively greater shear force affects the CrCLs in stifle joints with partial CrCL ruptures.     

Nitric oxide and metalloproteinases in canine articular ligaments: a comparison between the cranial cruciate, the medial genual collateral and the femoral head ligament

Osteoarthritis due to cranial cruciate ligament (CCL) rupture or hip dysplasia is one of the most important causes of chronic lameness in dogs. This study aimed at comparing nitric oxide (NO) production by the CCL with that of the femoral head ligament (FHL) and the medial collateral ligament (MCL), and investigating the pathway of NO production and the concomitant metalloproteinase (MMP) activity in the presence or absence of an inflammatory stimulus. Ligaments of normal dogs were subjected to different stimuli, and NO and MMP activity from explant culture supernatants were compared. The results showed that in explant cultures of the canine CCL more NO was produced than in those of the other two ligaments. A higher level of NO was produced when CCLs were exposed to the inducible nitric oxide synthase (iNOS)-inducing cocktail TNF/IL-1/LPS, and NO synthesis could be inhibited by both l-NMMA, a general nitric oxide synthase (NOS) inhibitor and l-NIL, a specific iNOS inhibitor. However, a correlation between NO synthesis and iNOS expression levels as determined by immunohistochemistry was not observed. In contrast to CCL, no evidence for iNOS-dependent NO synthesis was observed for MCL and FHL. The CCL produced less MMP than MCL and FHL, and no correlation between MMP and NO could be demonstrated. MMP activity in the CCL increased significantly after 48 h of incubation with the inflammatory stimulus. The results suggest that in canine osteoarthritis NO synthesized by canine CCL plays a more important role in the pathogenesis of osteoarthritis of the stifle than that synthesized by FHL and MCL.     

前十字韧带断裂犬胫骨平台角的X线和CT测量

为探究胫骨平台角（tibial plateau angle,TPA）在犬前十字韧带断裂（cranial cruciate ligament rupture,CCLR）中的临床意义及为犬CCLR的整体发病规律与风险、诊断和治疗方案提供参考,本研究选用2018年6月至2019年1月在中国农业大学动物医院确诊为CCLR的共15只患犬的30个膝关节,使用X线和CT测量TPA （R-TPA和CT-TPA）并比较X线和CT测量TPA的一致性及优缺点。结果显示,R-TPA大小与年龄、体重、胖瘦、性别及绝育/去势与否均无关（P>0.05）,前十字韧带是否断裂亦与TPA大小无关（P>0.05）。经CT测量所得30个CT-TPA的平均值为26.93°（范围：19.03°~32.67°）;左侧膝关节的CT-TPA的平均值为26.82°,右侧为27.04°。R-TPA与CT-TPA值具高度相关性（r>0.75,P>0.05）;21个膝关节（70%）可在CT图像中观察到骨赘生成,其CT图像比X线图像能更清楚地辨识出骨赘与骨皮质的分界。结果表明,TPA与CCLR患犬的临床病理因素无关,X线与CT在测量犬TPA方面具有一致性,CT测量在测量图像的采集上较X线拍摄更方便、快捷与全面,并在骨关节炎病例中的测量精度更高。     

Immunopathological mechanisms in dogs with rupture of the cranial cruciate ligament

The majority of studies on cranial cruciate ligament (CrCL) disease to date have been carried out on dogs that already sustained a CrCL rupture, which is the end-stage of the disease. Investigations have recently been carried out to study humoral and cellular immunopathological mechanisms in predisposed dogs before clinical rupture of the contralateral CrCL. The cruciate ligaments are mainly composed of collagen type I, and immune responses to collagen have been suggested as a cause of CrCL degradation in dogs. None of these investigations showed evidence that anticollagen type I antibodies alone initiate CrCL damage. However, in predisposed dogs a distinct anticollagen type I antibody gradient was found towards the contralateral stifle joint that eventually sustained a CrCL rupture, suggesting that there was an inflammatory process present in these joints before detectable joint instability occurred. The importance of cellular reactivity to collagen type I in cruciate disease also remains unclear. Peripheral blood mononuclear cell proliferation to collagen type I was very diverse in dogs with cruciate disease whereas some sham operated dogs and healthy dogs tested positive as well. It is not yet determined whether cellular reactivity to collagen type I exists locally in the stifle joints nor whether this could initiate CrCL degradation. Inflammatory processes within the stifle joint can alter the composition of the cruciate ligaments. In animal models of immune-mediated synovitis, the mechanical strength of the CrCL is significantly reduced. Immunohistochemical studies on synovial tissues from dogs with rheumatoid arthritis and dogs with cruciate disease revealed that the pathologic features are similar in both joint pathologies and that the differences are mainly quantitative. Joint inflammation induced by biochemical factors such as cytokines has been implied in CrCL degeneration. In several studies, the levels of pro-inflammatory and T helper cytokines were measured in dogs that sustained a CrCL rupture, but the exact role of the various cytokines in the pathogenesis of CrCL disease remains inconclusive. More recently, the levels of the cytokines have been investigated over time in predisposed dogs before and after CrCL rupture. IL-8 expression tended to be higher in stifle joints that will rupture their CrCL during the next 6 months than in those that will not, indicating an inflammatory process in these joints before clinical rupture. This review provides a comprehensive overview of all possible implications of humoral and cell-mediated immune responses published in dogs with cruciate disease together with publications from human joint diseases. Furthermore, this review highlights recent findings on cytokines and proteinases in the accompanying joint inflammation.     

ULTRASONOGRAPHIC EVALUATION OF CRANIAL CRUCIATE LIGAMENT RUPTURE VIA DYNAMIC INTRA-ARTICULAR SALINE INJECTION

Ultrasonographic examination of both stifle joints of five clinically and radiographically normal adult dogs was performed before and after surgical transection of the cranial cruciate ligament (CrCL). At pre- and postsurgery, the hyperechoic patellar ligament and the infrapatellar fat interfered with sonographic visualization of the CrCL. When the stifle joint, however, was imaged via dynamic intra-articular saline injection, the hyperechoic ligament was visualized because of the separation of the infrapatellar fat and the CrCL and the contrasting effect of anechoic saline. When the stifle joint was imaged by real-time scanning after the transection of the CrCL, flutter of the ligament and an anechoic area between the bone and the CrCL were identified. The increased diameter of the ligament and the increased thickness of the joint space were identified as well. Ultrasonographic examination via dynamic saline injection into the joint space has potential as a diagnostic tool for assessing CrCL rupture.