1H NMR metabolic profiling of synovial fluid from patients with anterior cruciate ligament tears and hemarthrosis.

OBJECTIVE: To compare the metabolic profiles of synovial fluid (SF) from patients with anterior cruciate ligament tears and hemarthrosis (HA) with that of normal controls, using 1H NMR spectroscopy (NMRS). METHODS: Synovial fluid was collected from eleven patients undergoing arthroscopic debridement within 14 days following an anterior cruciate ligament (ACL) tear and hemarthrosis. Ten additional SF samples were obtained from the knees of osteoarthritis-free volunteers to serve as normal controls. The relative concentrations of twenty-eight endogenous SF metabolites (hydroxybutyrate, acetate, acetoacetate, acetone, alanine, arginine, choline, citrate, creatine, creatinine, formate, glucose, glutamate, glutamine, glycerol, glycine, histidine, isoleucine, lactate, leucine, lysine, phenylalanine, proline, pyruvate, threonine, tyrosine, valine, and the mobile components of glycoproteins and lipids) were evaluated using NMRS and quantified using CHENOMX metabolomics analysis software. Mean differences between groups were evaluated with t-tests controlling for multiple comparisons at an overall error rate of 0.10. RESULTS: Statistically significant increases in the levels of glucose, choline, the branched-chain amino acids leucine, isoleucine, and valine, and the mobile components of N-acetyl glycoproteins and lipids were observed in ACL/HA SF as compared with normal controls; lactate levels were reduced. CONCLUSIONS: Marked changes occur in the metabolic profiles of human knee fluid following ACL injury and hemarthrosis, suggestive of increased demand and accompanying inflammatory response; potentially increased lipid and glucose metabolism; and possible hyaluronan degradation within the joint following trauma.

From gene expression to serum proteins: biomarker discovery in ankylosing spondylitis.

OBJECTIVES: Studying post-infliximab gene expression changes could provide insights into the pathogenesis of ankylosing spondylitis (AS). METHODS: Gene expression changes were screened by microarray on peripheral blood RNA of 16 AS patients at baseline and 2 weeks post-infliximab, and selected results were confirmed by quantitative real-time (qRT)-PCR. Corresponding serum-soluble LIGHT (sLIGHT) was estimated by ELISA and the fold change in sLIGHT was correlated to the fold change in erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and the Bath AS disease activity index. RESULTS: Post-infliximab, 69% of the patients (11/16) achieved an ASAS20 response. Six candidate genes were differentially expressed by microarray; four of which were validated by qRT-PCR. sLIGHT showed the most significant difference. There was good correlation of baseline sLIGHT with CRP (R = 0.60; p = 0.01) and ESR (R = 0.51; p = 0.04). The fold change in sLIGHT correlated with change in both CRP (R = 0.71, p = 0.002) and ESR (R = 0.77, p<0.001). CONCLUSION: LIGHT is significantly downregulated by infliximab. sLIGHT correlated well with changes in inflammatory markers.

Isolation of picomolar affinity anti-c-erbB-2 single-chain Fv by molecular evolution of the complementarity determining regions in the center of the antibody binding site.

We determined the extent to which additional binding energy could be achieved by diversifying the complementarity determining regions (CDRs) located in the center of the antibody combining site of C6.5, a human single-chain Fv (scFv) isolated from a non-immune phage library which binds the tumor antigen c-erbB-2. CDR3 of the light (V(L)) and heavy (V(H)) chain variable region of C6.5 were sequentially mutated, the mutant scFv displayed on phage, and higher affinity mutants selected on antigen. Mutation of V(L) CDR3 yielded a scFv (C6ML3-9) with a 16-fold lower Kd (1.0 x 10(-9) M) than C6.5. Due to its length of 20 amino acids, four V(H) CDR3 libraries of C6ML3-9 were constructed. The greatest increase in affinity from a single library was ninefold (Kd = 1.1 x 10(-10) M). Combination of mutations isolated from separate V(H) CDR3 libraries yielded additional ninefold decreases in Kd, resulting in a scFv with a 1230-fold increase in affinity from wild-type C6.5 (Kd = 1.3 x 10(-11) M). The increase in affinity, and its absolute value, are comparable to the largest values observed for antibody affinity maturation in vivo or in vitro and indicate that mutation of V(L) and V(H) CDR3 may be a particularly efficient means to increase antibody affinity. This result, combined with the location of amino acid conservation and substitution, suggests an overall strategy for in vitro antibody affinity maturation. In addition, the affinities and binding kinetics of the single-chain Fv provide reagents with potential tumor targeting abilities not previously available.

Activity of single-agent melphalan 220-300 mg/m2 with amifostine cytoprotection and autologous hematopoietic stem cell support in non-Hodgkin and Hodgkin lymphoma.

High-dose chemotherapy using melphalan (HDMEL) is an important component of many conditioning regimens that are given before autologous hematopoietic stem cell transplantation (AHSCT). In contrast to the situation in myeloma, and to a lesser degree acute leukemia, only a very limited published experience exists with the use of HDMEL conditioning as a single agent in doses requiring AHSCT for lymphoma, both Hodgkin lymphoma (HL) and especially non-Hodgkin lymphoma (NHL). Thus, we report results of treating 26 lymphoma patients (22 with NHL and four with HL) with HDMEL 220-300 mg/m(2) plus amifostine (AF) cytoprotection and AHSCT as part of a phase I-II trial. Median age was 51 years (range 24-62 years); NHL histology was varied, but was aggressive (including transformed from indolent) in 19 patients, indolent in two patients and mantle cell in one. All 26 patients had been extensively treated; 11 were refractory to the immediate prior therapy on protocol entry and two had undergone prior AHSCT. All were deemed ineligible for other, 'first-line' AHSCT regimens. Of these 26 patients, 22 survived to initial tumor evaluation on D +100. At this time, 13 were in complete remission, including four patients who were in second CR before HDMEL+AF+AHSCT. Responses occurred at all HDMEL doses. Currently, seven patients are alive, including five without progression, with a median follow-up in these latter patients of D +1163 (range D +824 to D +1630); one of these patients had a nonmyeloablative allograft as consolidation on D +106. Conversely, 14 patients relapsed or progressed, including five who had previously achieved CR with the AHSCT procedure. Two patients, both with HL, remain alive after progression; one is in CR following salvage radiotherapy. Six patients died due to nonrelapse causes, including two NHL patients who died while in CR. We conclude that HDMEL+AF+AHSCT has significant single-agent activity in relapsed or refractory NHL and HL. This experience may be used as a starting point for subsequent dose escalation of HDMEL (probably with AF) in established combination regimens.

A technique for recording from single neurons in the spinal cord of the awake cat.

A means of recording activity from single neurons in the spinal cord of the awake cat over periods of several weeks is described. The method combines elements of the chronically implanted well technique used in recording from supraspinal structures, with a novel method for reversibly stabilizing the vertebral column in a detachable 'outrigger' device. Between recording sessions, the animal is therefore freely mobile, its vertebral column again flexible. This preparation allows exploration of 1 cm2 of the spinal cord to all depths, and single neurons can be held for periods of 30 min to 2 h. The activity of primary afferents, intraspinal interneurons and motoneurons can be identified and their responses quantified during limb movement by combining ancillary techniques with the stabilization method.

Granulocyte-colony stimulating factor (G-CSF)-primed, delayed marrow harvests as a source of hematopoietic stem and progenitor cells for allogeneic transplantation.

We evaluated the ability of G-CSF to increase the number of hematopoietic stem cells obtained by "delayed" BM harvest for allogeneic transplantation. Five normal donors received G-CSF @ 10 mcg/kg/day x 5 followed by repeat PB and BM assays at day 6 and 16, and BM harvest at day 16. Stem cells were not increased in the BM at day 16. Five patients underwent BMT and engrafted at +10 to +19 days. While the tested strategy offers no intrinsic advantages, its potential cannot be evaluated fully without alternative timing and/or additional, "early acting" growth factors.

Amelioration of disease severity by intraarticular hylan therapy in bilateral canine osteoarthritis.

Because of its high molecular weight, the glycosaminoglycan molecule hyaluronan is responsible for the viscoelastic properties of normal synovial fluid. In osteoarthritis, the concentration and molecular weight of hyaluronan in synovial fluid is diminished: this impairs the ability of synovial fluid to effectively lubricate joints, absorb loads, and exert anti-inflammatory effects. Using a bilateral anterior cruciate-ligament transection and partial neurectomy canine model of osteoarthritis, this study examined the effect of viscosupplementation with hylan G-F 20 as a treatment for osteoarthritis. Twelve dogs underwent bilateral arthroscopic anterior cruciate-ligament transections and partial neurectomy of the knee joints. Beginning 1 week after the operation, six dogs received three weekly 500-microl injections of hylan G-F 20 in one knee and a sham injection of saline solution in the contralateral knee (early-treatment group). The remaining six animals underwent the same treatment 2 months following the procedure (late-treatment group). All dogs were killed at 8 months, and both knees were evaluated for gross pathology, histology, and proteoglycan content. In addition, with use of 500-MHz [1H] magnetic resonance spectroscopy, the synovial fluid from both knees was assessed for changes in metabolic profile. Differences in outcome were analyzed with paired t tests. Gross pathological and histological examination revealed significantly less severe changes of osteoarthritis in knees treated with hylan G-F 20 2 months after surgery than in the contralateral untreated knees. Magnetic resonance spectroscopy of the specimens in this late-treatment group showed significantly decreased glucose concentrations and significantly elevated isoleucine levels in the synovial fluid from knees treated with hylan G-F 20 compared with the controls. Previous magnetic resonance spectroscopy had shown that glucose concentrations increase with the onset of osteoarthritis and eventually diminish in end-stage osteoarthritis. The three injections of hylan were given after osteoarthritis was established, and the severity of the disease was ameliorated in the treated knees 6 months after treatment. This occurred although hylan G-F 20 is almost certainly cleared from joints by lymphatics within 4 weeks of injection, suggesting that hylan therapy can retard the progression of osteoarthritis for periods of time extending beyond the intraarticular residence time of the injected molecules and that hylan injections given at relatively early stages of osteoarthritis may have a chondroprotective effect. No changes in outcome were noted in the animals that received hylan G-F 20 immediately following surgery.

Quantitation of articular cartilage using magnetic resonance imaging and three-dimensional reconstruction.

A quadrature knee coil was used in conjunction with a magnetic resonance imaging scanner for quantitation of test phantom volumes, ex vivo bovine cartilage thickness, and in vivo human articular cartilage volumes. Optimal magnetic resonance parameters were obtained by testing a series of spin-echo and gradient-echo pulse sequences to determine the sequence that provided the highest resolution of articular cartilage and best defined the cartilage interfaces with synovial fluid and subchondral bone. Extensive testing revealed that two sequences were required to define articular cartilage accurately: a spoiled gradient-echo sequence and a steady state free-precession sequence. Three-dimensional reconstruction and statistical analyses of test phantoms and of bovine and human cartilage images were performed. Differences between actual phantom volumes and three-dimensional measurements demonstrated that, as magnetic resonance slice thickness was increased, the measurement variability also increased (coefficient of variation ranging from 1.7 +/- 1.3% for 1.0 mm slice thickness to 22.7 +/- 1.9% for 3.0 mm slice thickness). When the phantom volume was greater than 1,800 mm3, the intraobserver, interobserver and interscan accuracies were greater than 97, 98, and 96%, respectively. This high degree of reproducibility pertained for the data on in vivo human cartilage data also. For experienced observers, the intraobserver and interobserver reproducibility were greater than 98 and 97%, respectively. The interscan reproducibility was greater than 98%. These data demonstrate that improved magnetic resonance pulse sequencing, in conjunction with three-dimensional reconstruction and measurement techniques, can accurately and reproducibly measure the volume of articular cartilage. Clinical application of this approach offers the potential for early diagnosis of osteoarthritis and for serial, noninvasive assessment of changes in articular cartilage volume in response to therapeutic modalities.

Comparative study of normal and osteoarthritic canine synovial fluid using 500 MHz 1H magnetic resonance spectroscopy.

High resolution 1H nuclear magnetic resonance spectroscopy has been used to investigate and compare the metabolic profiles of normal and osteoarthritic synovial fluids in a canine model of osteoarthritis. The spectra of osteoarthritic synovial fluid showed (a) increased concentrations of lactate, pyruvate, lipoprotein-associated fatty acids, and glycerol as well as the ketones hydroxybutyrate and hydroxyisobutyrate, (b) reduced levels of glucose, and (c) elevated levels of N-acetylglycoproteins, acetate, and acetamide compared with healthy normal canine synovial fluid. An increase was also observed in the concentrations of the amino acids alanine and isoleucine. These results suggest that (a) the intraarticular environment in canine osteoarthritis is more hypoxic and acidotic than in a normal joint, (b) lipolysis may play an increasingly important role as a source of energy in osteoarthritis, and (c) the N-acetylglycoprotein polymer component of synovial fluid (mostly hyaluronan) seems to be increasingly fragmented and degraded into acetate by way of an acetamide intermediate with progressive osteoarthritis. The observed changes in the biochemical profile of canine osteoarthritic synovial fluid may be useful in understanding alterations in joint metabolism consequent to arthritic diseases and helpful in identifying potential markers of osteoarthritis.

Air bag-related deaths and serious injuries in children: injury patterns and imaging findings.

BACKGROUND AND PURPOSE: As of November 1, 1997, automotive air-bag deployments occurring in low-speed collisions had resulted in the deaths of 49 children and in the serious injuries of 19 children in the United States. The purpose of this study was to investigate the patterns of injury occurring in this new mechanism of pediatric trauma. METHODS: In search of common patterns of injury, three pediatric radiologists retrospectively evaluated the available autopsy and imaging studies in 11 such cases not previously reported in the medical literature, in addition to three published case studies. RESULTS: The cause of death or serious injury in every case was the direct result of neurologic injury. Injury patterns differed according to the child's age and type of restraint used at the time of collision. Crush injury to the skull predominated in infant victims traveling in rear-facing child safety seats, and both cranial and cervical spine trauma occurred in older children traveling restrained, improperly restrained, or unrestrained in the vehicle's front passenger seat. CONCLUSION: Air-bag systems pose a potentially fatal threat to the front-seat child passenger. This is directly related to the biomechanics at impact placing the child closer to the deploying air bag. An understanding of the biomechanics provides the radiologist insight into the two types of injury patterns observed.

How well does applicant rank order predict subsequent performance during radiology residency?

RATIONALE AND OBJECTIVES: Residency selection committees expend substantial time and resources on assessing the quality of residency applicants to derive an appropriate rank order for the National Residency Matching Program. The authors determined whether there is a relationship between the rank number or rank percentile of applicants selected for a residency training program and subsequent radiology residency performance. MATERIALS AND METHODS: Records of radiology residents completing their residency between 1991 and 1998 were reviewed. Available rank numbers and rank percentiles for each resident were compared with subsequent performance, as assessed subjectively by 4th-year radiology rotation evaluation forms and retrospective recall of four senior faculty members and objectively by numerical and percentile scores on the written portion of the American Board of Radiology (ABR) examinations. Correlation coefficients were obtained for each comparison. RESULTS: Rank number and rank percentile were not significantly correlated with 4th-year resident rotation evaluations or ABR written examination scores or percentiles. A small correlation existed between rank order and retrospective evaluation of resident performance by the four senior faculty. CONCLUSION: Applicant rank number and rank percentile do not correlate with subsequent radiology residency performance as assessed on rotation evaluation forms or the ABR written examinations.

Prenatal diagnosis of congenital cystic adenomatoid malformation and its postnatal presentation, surgical indications, and natural history.

BACKGROUND/PURPOSE: Regression of a cystic adenomatoid malformation (CAM) in a fetus is well described. Little, however, is known about the postnatal course of these infants. This study attempts to correlate the prenatal course of CAMs with postnatal symptoms, radiological manifestations, and need for surgery. METHODS: The clinical course of patients with a CAM diagnosed prenatally were retrospectively reviewed. Inclusion in the study required a prenatal ultrasound scan documenting a CAM. RESULTS: Over 10 years, 14 patients with a CAM were diagnosed prenatally. Six (43%) showed a partial in utero regression. Four patients were symptomatic at birth and underwent a resection as newborns. Ten patients were asymptomatic at birth, and eight of these had normal chest x-rays. Elective resection has been performed in 3 of these 10, and two additional children are scheduled to undergo an excision near 1 year of age. The remaining five patients have undergone follow-up nonoperatively for a mean of 36 +/- 15 months. Of the seven asymptomatic patients not undergoing immediate surgery, only one has shown a slight postnatal regression, despite five of these showing regression in utero. None have become symptomatic. CONCLUSIONS: The results suggest that regression of a CAM on prenatal ultrasound scan is common, but this process does not continue after birth. A normal chest x-ray does not indicate complete regression of a CAM; a computed tomography (CT) scan is required to evaluate such patients, and will generally demonstrate a CAM. Asymptomatic patients with a CAM may be followed up nonoperatively with no apparent adverse effects. The decision and timing of an excision in an asymptomatic patient remains controversial among pediatric surgeons.

Practical implications of cyclooxygenase-2--specific inhibitors in orthopedics.

Nonsteroidal anti-inflammatory drugs (NSAIDs) lead to severe and unpredictable side effects that are costly for individuals and the economy overall. As baby boomers enter their osteoarthritis years, there will be an increasing demand for safe and effective arthritis therapies. Animal and human data suggest that celecoxib, a cyclooxygenase-2-specific inhibitor, will provide an efficacious treatment without the side effects of conventional NSAIDs. Clinicians will need to determine individually and collegially how best to incorporate this new class of drugs into comprehensive treatment algorithms.

Blood-based biomarkers for detecting mild osteoarthritis in the human knee.

OBJECTIVE: This study was designed to test the utility of a blood-based approach to identify mild osteoarthritis (OA) of the knee. METHODS: Blood samples were drawn from 161 subjects, including 85 subjects with arthroscopically diagnosed mild OA of the knee and 76 controls. Following RNA isolation, an in-house custom cDNA microarray was used to screen for differentially expressed genes. A subset of selected genes was then tested using real-time RT-PCR. Logistic regression analysis was used to evaluate linear combinations of the biomarkers and receiver operating characteristic curve analysis was used to assess the discriminatory power of the combinations. RESULTS: Genes differentially expressed (3543 genes) between mild knee OA and control samples were identified through microarray analysis. Subsequent real-time RT-PCR verification identified six genes significantly down-regulated in mild OA: heat shock 90kDa protein 1, alpha; inhibitor of kappa light polypeptide gene enhancer in B-cells, kinase complex-associated protein; interleukin 13 receptor, alpha 1; laminin, gamma 1; platelet factor 4 (also known as chemokine (C-X-C motif) ligand 4) and tumor necrosis factor, alpha-induced protein 6. Logistic regression analysis identified linear combinations of nine genes--the above six genes, early growth response 1; alpha glucosidase II alpha subunit; and v-maf musculoaponeurotic fibrosarcoma oncogene homolog B (avian)--as discriminatory between subjects with mild OA and controls, with a sensitivity of 86% and specificity of 83% in a training set of 78 samples. The optimal biomarker combinations were then evaluated using a blind test set (67 subjects) which showed 72% sensitivity and 66% specificity. CONCLUSIONS: Linear combinations of blood RNA biomarkers offer a substantial improvement over currently available diagnostic tools for mild OA. Blood-derived RNA biomarkers may be of significant clinical value for the diagnosis of early, asymptomatic OA of the knee.

Intra-articular hyaluronan therapy.

The hyaluronan in normal synovial fluid plays an important role in joint homeostasis. It contributes to joint lubrication, buffers load transmission across articular surfaces, provides a renewed source of hyaluronan to joint tissues, and imparts antinociceptive and anti-inflammatory properties to synovial fluid. In osteoarthritis, the molecular weight and concentration of hyaluronan in synovial fluid are diminished. This has led to the proposition that removal of pathologic osteoarthritic synovial fluid and replacement with hyaluronan-based products that restore the molecular weight and concentration of hyaluronan toward normal levels can have beneficial therapeutic effects. This form of treatment for osteoarthritis has been termed viscosupplementation. Within the musculoskeletal community there are diverse opinions, ranging from skepticism to acceptance, about viscosupplementation as a mainstream symptom-modifying osteoarthritis therapy. This review focuses on recent basic and clinical studies dealing with mechanism of action, symptomatic efficacy, safety, and disease modification, and places these studies in context with earlier studies.

Joint receptors modulate short and long latency muscle responses in the awake cat.

Nerve cuff electrodes were chronically implanted around multiple peripheral nerves in adult cats, including the medial and posterior articular nerves (MAN and PAN) to the knee while EMG electrodes were implanted into seven hindlimb muscles. Randomized load perturbations producing mid-range knee flexions at varying angular velocities were subsequently applied to awake cats. Recordings were initially obtained with knee joint innervation intact and then after local anaesthetic or saline control solution was injected into the knee. Averaged neurogram and EMG responses to the imposed movements were utilized to assess the contribution of joint mechanoreceptor activity to the evoked muscle responses. Additionally, spike-triggered averaging techniques and peri-stimulus time histograms of single joint afferent units isolated from the articular nerve cuffs were utilized to characterize unitary joint receptor responses. The averaged whole nerve response to knee joint perturbations on each of the cuffed articular nerves revealed phasic increases in activity relative to constant background levels. The earliest phasic responses on the articular nerves were initiated at latencies that were too short to be voluntary, occurring in the short latency (reflex) period. Detectable joint receptors were not recruited until after the earliest excitatory responses of agonist/antagonist muscle pairs acting across the knee had occurred, presumably resulting in mechanical loading of the knee joint capsule and subsequent activation of articular mechanoreceptors. Introduction of local anaesthetic into the knee was accompanied by marked diminution in joint afferent activity. Perturbation-evoked muscle responses were characterized by increased activity above background levels in all seven muscles studied, including antagonist muscle pairs. Local anaesthetic-mediated loss of knee joint mechanoreceptor input altered the latency, amplitude and duration of EMG responses in each muscle. The effect of joint anaesthesia in the short latency period was a generalized decrease in all muscle responses relative to normal and saline controls. The loss of afferent input after joint anaesthesia was also associated with altered muscle responses during the long latency period, when both reflex and voluntary mechanisms could potentially contribute to the generation of EMG activity. Interestingly, long latency activity after joint anaesthesia was characterized by "unbalancing" in the EMG responses of some antagonist muscle pairs. This alteration of normal antagonist pair co-contraction patterns served to increase the magnitude of the imposed perturbations, rather than to bring the movements under control. Analysis of single joint afferents isolated from whole joint nerve recordings demonstrated that some joint afferent units were tonically active at quiescent, mid-range knee positions. Additionally, isolated afferents demonstrated different time courses of response to imposed perturbations.(ABSTRACT TRUNCATED AT 400 WORDS)

Engineering and characterization of a novel fusion protein incorporating B7.2 and an anti-ErbB-2 single-chain antibody fragment for the activation of Jurkat T cells.

The provision of the T-cell costimulatory molecule B7 to tumor cells can be an effective way to trigger a tumor-specific cytolytic T-cell response. One way to provide B7 to tumor cells would be to couple an antitumor antibody directly to B7. Such a molecule should target tumors displaying antigen and provide the costimulatory signal to T cells, resulting in the initiation of an antitumor T-cell response. To this end, a fusion protein was designed that incorporates a single-chain antibody fragment (scFv) to erbB-2 (Her2/neu), an oncogene product overexpressed by 30% to 50% of breast carcinomas, and the ECD of B7-2 (CD86). This fusion protein, expressed and purified from Pichia pastoris, was shown to retain binding activity to both counter receptors, erbB-2 and CD28. The fusion protein was also shown to target erbB-2-positive tumor cells and to deliver a CD28-specific T-cell costimulatory signal. These results suggest that a fusion protein engineered to target tumor cells and signal T cells for activation may be an effective means of cancer immunotherapy. Further studies should be performed to characterize the fusion protein in erbB-2 tumor-bearing mice for in vivo tumor targeting, biodistribution, and efficacy.

Arthroscopic anterior cruciate ligament transection induces canine osteoarthritis.

OBJECTIVE: To determine whether arthroscopic anterior cruciate ligament (ACL) transection in the canine knee can be an effective alternative method for creating canine osteoarthritis (OA). METHODS: Six adult dogs underwent arthroscopic examination of the left knee with a 2.7 mm 30 degrees fiberoptic arthroscope. The articular surfaces of the femoral condyles, tibial plateaus, and patella were examined for evidence of OA. The ACL was directly visualized and transected. Care was taken to avoid iatrogenic articular cartilage injury. The animals were sacrificed 2 to 6 months after ACL transection. Both the ACL transected and ACL intact knees from each animal were assessed for gross pathology and histology. RESULTS: The dogs experienced minimal perioperative pain and rapidly returned to their preinjury level of activity. Gross and histological examination of articular cartilage confirmed this approach induced OA in every ACL transected knee. No contralateral ACL intact knee developed degenerative OA changes. CONCLUSION: Arthroscopic ACL transection is an effective method for creating canine OA. This approach has several methodological advantages relative to other techniques.