Magnetic resonance imaging of osteoarthritis: correlation with gross pathology using an experimental model

Moving Beyond the Limits of Detection: The Past, the Present, and the Future of Diagnostic Imaging in Canine Osteoarthritis

Osteoarthritis (OA) is the most common orthopedic condition in dogs, characterized as the chronic, painful end-point of a synovial joint with limited therapeutic options other than palliative pain control or surgical salvage. Since the 1970s, radiography has been the standard-of-care for the imaging diagnosis of OA, despite its known limitations. As newer technologies have been developed, the limits of detection have lowered, allowing for the identification of earlier stages of OA. Identification of OA at a stage where it is potentially reversible still remains elusive, however, yet there is hope that newer technologies may be able to close this gap. In this article, we review the changes in the imaging of canine OA over the past 50 years and give a speculative view on future innovations which may provide for earlier identification, with the ultimate goal of repositioning the limit of detection to cross the threshold of this potentially reversible disease.

Comparison of High-field and Low-field Magnetic Resonance Imaging of Stifle Joint Disorders in Dogs

The most common cause of hindlimb lameness in dogs is cranial cruciate ligament rupture. In 48-77.3% of the population this trauma leads to secondary damage of the meniscus. Depending on the magnetic strength of the used device, different diagnostic accuracy can be achieved. The examination sensitivity of magnetic resonance imaging is affected by many factors which are independent of diagnostic strength, such as correct positioning of the patient, size of the stifle joint examined, or selection of the right protocol of sequences. Sensitivity of meniscus damage detection was 100% and 90%, respectively, in high- and low-field magnetic resonance. The best results were reported during examination of the stifle in dogs above 10 kg b.w. at a flexion angle of 145°, and in sagittal and dorsal planes. Regardless of the magnetic strength applied, imaging of the whole cranial cruciate ligament is difficult. Moreover, MRI allows the detection of the first signs of osteoarthritis, which were observed 4 and 6 weeks after rupture of the cranial cruciate ligament using high and low-field MRI. This also applies to lesions in the subchondral bone or a bone marrow which occurred in association with insufficiency of the stifle joint, and were mainly localized in the epiphysis of the femur and tibia. The present article provides a comparison of different examination protocols and images of damaged stifle structures, such as menisci, ligaments and bones of the stifle joint visualized with low-field and high-field magnetic resonance. Magnetic resonance arthrography is also discussed.

Animal Models of Osteoarthritis: Comparisons and Key Considerations

Osteoarthritis (OA) is unquestionably one of the most important chronic health issues in humans, affecting millions of individuals and costing billions of dollars annually. Despite widespread awareness of this disease and its devastating impact, the pathogenesis of early OA is not completely understood, hampering the development of effective tools for early diagnosis and disease-modifying therapeutics. Most human tissue available for study is obtained at the time of joint replacement, when OA lesions are end stage and little can be concluded about the factors that played a role in disease development. To overcome this limitation, over the past 50 years, numerous induced and spontaneous animal models have been utilized to study disease onset and progression, as well as to test novel therapeutic interventions. Reflecting the heterogeneity of OA itself, no single "gold standard" animal model for OA exists; thus, a challenge for researchers lies in selecting the most appropriate model to answer a particular scientific question of interest. This review provides general considerations for model selection, as well as important features of species such as mouse, rat, guinea pig, sheep, goat, and horse, which researchers should be mindful of when choosing the "best" animal model for their intended purpose. Special consideration is given to key variations in pathology among species as well as recommended guidelines for reporting the histologic features of each model.

Arthroscopic treatment of fragmented coronoid process with severe elbow incongruity. Long-term follow-up in eight Bernese Mountain Dogs

The purpose of this study was to investigate the long-term treatment results of fragmented coronoid process (FCP) in joints with a radio-ulnar step greater than 3 mm. Treatment of these patients only consisted of fragment removal, without correction of the incongruity. The eight Bernese Mountain Dogs (11 joints) included in this study showed obvious clinical signs of elbow disease and were diagnosed with severe elbow incongruity and concomitant FCP in the time period from 1999-2003. At that time, elbow radiography, computed tomography, and arthroscopy were performed. The mean follow-up period was 5.6 years. The follow-up consisted of a telephone questionnaire combined with a clinical and radiographic re-evaluation at our clinic. The questionnaire revealed that all dogs were either free of lameness or only lame following heavy exercise. One dog sporadically required medication after heavy exercise. The owner satisfaction rate was 100%. The clinical re-evaluation did not reveal any signs of pain or lameness in all cases. Range-of- motion was decreased in nine of the 11 elbows. Radiographs revealed an increase in severity of osteoarthritis in every case.In this case series, arthroscopic fragment removal without treatment of incongruity was demonstrated to be a valuable treatment option and may provide a satisfactory long-term outcome.

Morphological changes of the lateral meniscus in end-stage lateral compartment osteoarthritis of the knee

OBJECTIVE

The aim of this study was to evaluate the morphological changes of the lateral meniscus in end-stage lateral compartment osteoarthritis (OA) of the knee.

METHODS

One hundred fifty-eight knee joints from 133 patients that subsequently underwent total knee joint arthroplasty from January 2008 to December 2009 were enrolled. There were 26 men and 107 women. Their ages ranged from 56 to 81 (mean 67.4 ± 6.5 years). All study participants had complete obliteration of the lateral joint space identified by weight-bearing radiography. Meniscal position was assessed by measuring meniscal subluxation and meniscal height. The meniscal morphology was assessed using a modification of the whole-organ magnetic resonance imaging score (WORMS). The frequency of different meniscal morphology and their respective positions was calculated.

RESULTS

The predominant type (42.4%, 53.8% and 52.5% in the anterior horn, mid-body and posterior horn, respectively) of abnormal meniscal morphology was a complete maceration/destruction or complete resection. The anterior horn of non-macerated lateral meniscus was more subluxed than that of the non-macerated medial meniscus in patients with lateral OA.

CONCLUSION

This study suggests that the lateral meniscus in persons with end-stage lateral OA are mostly macerated or destroyed. Also, unlike isolated end-staged medial compartment OA, the anterior horn of the lateral meniscus in isolated end-stage lateral OA is commonly affected.

Osteophytosis, subchondral bone sclerosis, joint effusion and soft tissue thickening in canine experimental stifle osteoarthritis: comparison between 1.5 T magnetic resonance imaging and computed radiography

OBJECTIVE

To compare use of 1.5 T magnetic resonance imaging (MRI) and computed radiography (CR) for morphologic and temporal evaluation of osteophytosis, subchondral sclerosis, joint effusion, and synovial thickening in experimentally induced canine stifle osteoarthritis (OA).

STUDY DESIGN

Prospective study.

ANIMALS

Dogs (n=8).

METHODS

CR (mediolateral and caudocranial projections) and MRI (dorsal 3D T1-weighted gradient echo, sagittal 3D SPGR and T2-weighted fast spin echo with fat saturation) were performed at baseline (n=8) and at week 4 (n=5), week 8 (n=8), and week 26 (n=5) after cranial cruciate ligament transection. Osteophytosis, subchondral bone sclerosis, and joint effusion were scored on CR and MRI, and synovial thickening on MRI.

RESULTS

MRI was more sensitive than CR for detection of osteophytosis and could better discriminate joint effusion from soft tissue thickening, although scores for these variables strongly correlated between modalities (rho=0.94 [osteophytosis] and 0.80 [effusion]; P<.001). Scores for subchondral bone sclerosis also correlated (rho=0.54, P<.004), although this variable may have been over interpreted on CR. Joint effusion and synovial thickening peaked at week 8, before partially regressing at week 26. Conversely, osteophytosis and sclerosis progressed semi-linearly over 26 weeks.

CONCLUSION

MRI is more sensitive than radiography in assessing onset and progression of osteophytosis in canine experimental stifle OA and provides enhanced discrimination between joint effusion and synovial thickening.

CLINICAL RELEVANCE

MRI is as a more powerful imaging modality that should be increasingly used in animals to assess the joint related effects of disease-modifying OA drugs.

The relationship between limb function and radiographic osteoarthrosis in dogs with stifle osteoarthrosis

OBJECTIVE

To evaluate the relationship between limb function and radiographic evidence of stifle osteoarthrosis (OA) in dogs.

STUDY DESIGN

The relationship between force platform data and radiographic OA score was evaluated on 2 separate days using regression analysis. Interday variation was also assessed.

ANIMALS

Forty-one dogs with visible lameness and radiographic evidence of stifle OA.

METHODS

Force platform data were collected at a velocity of 1.7 to 2.0 m/s for 5 trials on day 1 and day 8. Radiographs taken on day 1 were scored using a previously reported OA scoring system.

RESULTS

No significant relationship was found between force platform data and OA score. No significant differences were found between any day 1 and day 8 force platform values.

CONCLUSIONS

Although radiographic evidence of stifle OA provides evidence of pathology, it does a poor job of representing limb function. In addition, the absence of significant differences between day 1 and day 8 values in this population of dogs supports use of only a single force platform evaluation before measuring a treatment effect.

CLINICAL RELEVANCE

The presence of OA in the stifle joint does not correlate with clinical function; radiographic outcome should be used cautiously as a predictor of clinical outcome.

Definition and epidemiology of osteoarthritis of the hand: a review

The hand is a common site of peripheral joint involvement in osteoarthritis (OA) and although often underestimated as a cause of disability, the effect on quality of life from limitations in performing activities of daily living such as dressing and feeding may be considerable. Hand OA may also be an important indicator of a systemic tendency to OA which may involve weight bearing joints, notably the hips and knees. (1) The definition of hand OA, particularly for epidemiological studies, has undergone reassessment and revision over the last few years. In this paper we examine the issues relating to this and consider the epidemiology of hand OA.

Low-field magnetic resonance imaging of the canine stifle joint: normal anatomy

Low-field magnetic resonance imaging (MRI) was performed on the stifle joints of four normal adult mongrel dogs using a 0.064 Tesla scanner. Markers were placed on each stifle joint to serve as reference points for comparing gross sections with the images. A T1-weighted sequence was used to image one stifle joint on each dog in the sagittal plane and the other stifle joint in the dorsal plane. The dogs were euthanized immediately following MRI and the stifle joints frozen intact. Each stifle joint was then embedded in paraffin, again frozen, and sectioned using the markers as reference points. On T1-weighted images, synovial fluid had low signal intensity (dark) compared to the infrapatellar fat pad which had a high signal intensity (bright). Articular cartilage was visualized as an intermediate bright signal and was separated from trabecular bone by a dark line representing subchondral bone. Menisci, fibrous joint capsule, and ligamentous structures appeared dark. In the true sagittal plane, the entire caudal cruciate ligament was often seen within one image slice. The patella was visualized as an intermediate bright signal (trabecular bone) surrounded by a low intensity signal (cortical bone). The trochlea and the intercondylar notch were difficult areas to analyze due to signal volume averaging of the curved surface of these areas and the presence of several types of tissues.

Origin of cartilage laminae in MRI

To understand the origin of the laminated appearance of cartilage in MRI (the magic angle effect), microscopic MRI (mu MRI) experiments were performed at 14-microns pixel resolution on normal canine articular cartilage from the shoulder joints. Two-dimensional images of the spin-spin relaxation time (T2) of the cartilage-bone plug at two angles (0 degree and 55 degrees) were calculated quantitatively. A distinct T2 anisotropy was observed as a function of the cartilage tissue depth. The surface and the deep regions exhibit strong orientational dependence of T2, whereas the upper-middle region exhibits little orientational dependence of T2. These three mu MRI regions correspond approximately to the three histologic zones in cartilage tissue. The results from the bulk T2 measurements agreed with these mu MRI results. Our studies show that the laminated appearance of cartilage in MRI is caused by T2 anisotropy of the tissue. We further suggest that the molecular origin of the T2 anisotropy is the nuclear dipolar interaction. The structure of the cartilage tissue indicates that the collagen meshwork defines this T2 anisotropy. The results show that the T2 anisotropy provides an indirect but sensitive indicator for the orientation of macromolecular structures in cartilage. The clinical implications of this anisotropy are discussed.

Increased levels of proteoglycan fragments and stromelysin in hip joint fluid in Legg-Calvé-Perthes disease

The concentrations of proteoglycan fragments and stromelysin were analyzed in joint aspirates in 19 children with Legg-Calvé-Perthes disease. We found increased levels of proteoglycan fragments and stromelysin consistent with the presence of synovitis, an important clinical and possibly also prognostic factor in these children.

Effects of functional electrical stimulation on the joints of adolescents with spinal cord injury

Nineteen adolescent subjects with complete spinal cord injuries resulting in paraplegia or tetraplegia participated in a functional electrical stimulation (FES) program consisting of computerized, controlled exercise and/or weight bearing. The effects of stimulated exercise and standing/walking on the lower extremity joints were prospectively studied. Plain radiographs and MRIs were obtained prior to and following completion of the exercise and standing and walking stages. In addition, the joints of five subjects were studied with synovial biopsies, arthroscopy, and the analysis of serum and synovial fluid for a 550 000 dalton cartilage matrix glycoprotein (CMGP). Pre-exercise joint abnormalities secondary to the spinal cord injury improved following the stimulation program. None of the subjects developed Charcot joint changes. Upon standing with FES, one subject with poor hip coverage prior to participation developed hip subluxation which required surgical repair. No other detrimental clinical effects occurred in the lower extremity joints of subjects participating in an FES program over a 1-year period.

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.

Osteoarthritis staging: comparison between magnetic resonance imaging, gross pathology and histopathology in the rhesus macaque

Although osteoarthritis (OA) is the most common cause of articular skeletal disability in humans, assessing progression (staging) with noninvasive methods remains a major clinical problem. Using the rhesus macaque animal model, the objective of this study was to compare OA staging by noninvasive magnetic resonance imaging (MRI) against gross pathology and histopathology. Right knee joints from 18 rhesus macaques were used in this study. Using a four-point ordinal scale for each of the above-mentioned modalities, the lateral and medial femoral condyle and tibial plateau of each knee joint was independently scored for OA severity, i.e. normal, mild OA, moderate OA and severe OA. Correlation between each staging system was performed using Stuart's Tau-c correlation coefficient. By our criteria, MRI staging correlated as well with gross pathology (tau = 0.75) and histopathology (tau = 0.80) as did gross pathology with histopathology (tau = 0.78). Our study shows that MRI is a promising noninvasive modality to evaluate the severity of OA. MRI appears to be sensitive for demarcating the presence and extent of focal OA cartilage lesions. However, at this time, while MRI is sensitive for detecting OA change it cannot distinguish between certain lesions such as superficial cartilage matrix fibrillation and hypertrophy both of which show elevated signal intensity.

Osteoarthritis and magnetic resonance imaging: potential and problems

To date, MRI has primarily been used to study anatomical changes, and at a resolution that makes detailed analysis of focal change difficult. This is primarily because cost limits the development and use of tailor made research systems. The detailed analysis of soft tissue, cartilage, and bone marrow images should provide a fruitful non-invasive method to study OA. However, the development of MRI methods to study movement, diffusion and perfusion, and the spatial localisation of spectroscopic information, promises a revolution in the study of the living joint in man.

High-resolution magnetic resonance imaging of arthritic pathology in the rat knee

High-resolution magnetic resonance imaging (MRI) has been used to visualise the changes that occur in both soft tissue and bone during antigen-induced, monoarticular arthritis (AIMA) of the rat knee. Extensive optimisation studies were performed in order to minimise the time of the experiments and to maximise both the signal-to-noise ratio and the contrast in the MR images. The study was cross-sectional rather than longitudinal and at each of the 13 time points studied during the progression of the disease, corresponding X-radiographs and histological sections were obtained. Interpretation of the spin echo MR images was aided by the use of chemical shift-selective imaging, magnetisation transfer contrast and relaxation time experiments, as well as by correlation with the histology and X-radiography data. The MR images clearly show invasion of the synovium by an inflammatory pannus which spreads over the articular cartilage and invades the bone, leading to erosion and later remodelling. Two distinct types of bony erosion were observed: focal erosions, especially at the margins of the joint, and subchondral erosions. It is concluded that MRI provides a sensitive, non-invasive method for investigating both early-stage inflammatory changes and late-stage bony changes in the knee joints of the arthritic rat.

Diagnostic imaging algorithm for cervical soft disc herniation

MRI with surface coils is currently the preferred method for evaluating degenerative cervical spine disease. The differentiation between soft disc herniation and osteophytic spurs is not always obvious, however, on a 0.5 Tesla unit. The procedure of choice for soft disc herniation, MRI on a 0.5 T superconducting system associated with plain radiography of the cervical spine, in selecting patients for anterior cervical discectomy without interbody fusion (ACD), was evaluated. This prospective study comprised 100 patients with cervical radicular symptoms, not subsiding after conservative treatment. Plain radiographs were obtained for all patients. Patients without spinal instability, spondylosis, or major osteophytes on plain radiographs and without clinical findings of myelopathy underwent MRI (n = 59) on a 0.5 Tesla superconducting system. The other 41 patients underwent CT myelography. On MRI, herniation of a cervical soft disc was seen in 55 patients and the localisation corresponded well with the clinical symptoms. CT myelography showed a foraminal herniation in one of four selected patients with negative MRI. Fifty of 55 patients underwent ACD. All herniations were confirmed at operation, but in two patients there were important foraminal spurs not seen on MRI. It is concluded that 0.5 T MRI combined with plain radiographs offers an accurate, non-invasive test in the assessment of selected patients with cervical radiculopathy.

Cervical neural foraminal canal stenosis: computerized tomographic myelography diagnosis

The surgical and computerized tomographic myelography (CTM) features of 134 stenotic foraminal canals were correlated retrospectively in 95 patients. The myelographic site of stenosis was the entrance to the foraminal canal in 70 cases (52%) and the canal itself in 37 (28%); the site was not identified definitively in 27 (20%). At the entrance to the foraminal canal, encroachment on the adjacent nerve root was by a cartilaginous cap in 10 cases (8%), a bony osteophyte in 17 (13%), a synovial cyst in one (1%), and a combination of a bony and cartilaginous osteophyte in 42 (31%). The diagnostic features of stenosis within the foraminal canal were more variable. Small bone spurs arising from the uncovertebral process encroached on the anterior aspect of the foramen in 29 instances (22%), accompanied in all cases by either a congenitally narrow canal (in 16) or a diffuse osteophytically narrowed canal (in 13); osteophytes arising from the superior facet in eight instances (6%) were larger and encroached on the posterior aspect of the foramen. Diagnosis on the basis of CTM is difficult because stenosis was readily evident as a bone spur in only 13% of cases, could not be distinguished from prolapsed disc in 39%, had to be differentiated from a congenitally narrow foraminal canal in 27%, and was frankly missed in 20% of the instances of stenosis.

Osteoarthritis in rhesus macaques: assessment of cartilage matrix quality by quantitative magnetic resonance imaging

To assess cartilage quality with anatomical location and extent of osteoarthritis (OA), magnetic resonance imaging (MRI) of the knee joint from rhesus monkeys was performed. MRI measurements--T1 and T2 relaxation times, proton density and cartilage thickness were taken from 8 equal segments of articular cartilage volumes extending from anterior to posterior edge of 1 mm sagittal slices. To grade the severity of OA in each quadrant of the knee joint a modified Mankin score was applied on the histological sections. Our results suggest that MR relaxation times and proton density values vary with the severity of osteoarthritis.

MR microimaging of articular cartilage and contrast enhancement by manganese ions

Saline solutions of manganese ions (Mn2+) were used as articular contrast agents in magnetic resonance microscopy (9.4 T) of cartilage of chicken femoral condyles and pig temporomandibular joints. The diffusion of Mn2+ from the articular surface into the cartilage matrix led to a strong contrast enhancement in the cartilage. The combination of the high spatial resolution and the contrast enhancement allowed the visualization of fine structures (tissue types) in the cartilage, which correlate with the tissue zones in histological sections stained with cationic dyes. We assume that the electrostatic interactions between the negatively charged groups of the proteoglycans and Mn2+ are most important for the mechanism of contrast enhancement. Hence, the different signal intensities of the various zones of cartilage indicate differences in density of proteoglycans. The intraarticular injection of the cationic contrast agent could improve the possibility of an early diagnosis of cartilage dysfunction and degeneration.

Experimental hyaline cartilage lesions: two-dimensional spin-echo versus three-dimensional gradient-echo MR imaging

The value of magnetic resonance (MR) imaging, with two-dimensional (2D) spin-echo and FISP (fast imaging with steady-state precession) and FLASH (fast low-angle shot) three-dimensional (3D) gradient-echo sequences, for the detection of hyaline cartilage defects of the femoral condyle and the tibial plateau, was investigated in an animal model. In eight dogs, the anterior cruciate ligament was transected in one knee joint, resulting in rapid development of osteoarthritis with degeneration of the hyaline cartilage. At autopsy, 24 cartilage lesions were found, which were classified into four grades. The overall detection of cartilage lesions with MR imaging was poor. Only five of the 24 lesions were visible on 2D spin-echo images, while 11 of 24 were visible on 3D FISP images and 15 of 24 were seen on 3D FLASH images. The best results were obtained in advanced stages of cartilage degeneration, involving ulceration and complete abrasion of the cartilage layer. Signal loss or signal intensity increase in the cartilage layer was seen inconsistently in grades 3 and 4 degeneration. In this animal model, 2D spin-echo imaging was inadequate for the diagnosis of hyaline cartilage lesions, while 3D gradient-echo imaging permitted satisfactory diagnosis in only grade 4 cartilage disease.

Quantitative imaging of osteoarthritis

Plain-film radiography currently remains the mainstay of imaging for diagnosis and follow-up in osteoarthritis (OA). However, recent studies have questioned some aspects of its use, particularly the correlation between radiographically evident joint-space narrowing and articular cartilage loss. The results with imaging modalities such as magnetic resonance imaging and ultrasound suggest that these methods will allow accurate noninvasive definition of the structure of articular cartilage and other soft tissues of joints. Other modalities, including microfocal radiography and high-resolution computed tomography, can produce detailed images of trabecular structure and bony alterations in osteoarthritis. Improvements in image analysis and data manipulation, including three-dimensional reconstruction and digitized storage and measurement of images, will likely enable improved quantitative assessment of the abnormalities demonstrated by these techniques. One can hope that such developments will facilitate not only improved detection and definition of OA, but also better evaluation of the effectiveness of pharmacological and physical therapy in practice and in clinical trials.

Magnetic resonance imaging in osteoarthritis of the knee: correlation with radiographic and scintigraphic findings

Twelve knees with a range of severity of knee osteoarthritis were assessed by magnetic resonance imaging (MRI) and technetium-99m labelled hydroxymethylene diphosphonate scintigraphy. Five magnetic resonance pulse sequences were evaluated. Proton density (TR = 1000, TE = 26 ms) and STIR (TR = 1500, TI = 100, TE = 30 ms) were chosen for further use. Abnormalities shown by MRI included joint effusions, meniscal disruption, hyaline cartilage thinning, subchondral signal changes, pseudocysts, and heterogeneity of signal from osteophytes. Certain MRI and scintigraphic appearances correlated: (a) 'hyperintense osteophytosis' and ipsilateral 'tramline' scintigraphic uptake, suggesting increased fat content in 'active' osteophytes; (b) subchondral signal change and 'extended' pattern, possibly reflecting inflammation, synovial leak, or fibrovascular repair; (c) patellofemoral joint signal changes and patellar isotope uptake.

The longitudinal course of hand osteoarthritis in a male population

In this prospective analysis of the natural history of osteoarthritis (OA) of the hand, the incidence and progression of various radiographic features of OA were examined in 177 men who participated in the Baltimore Longitudinal Study of Aging. Subjects who were less than 60 years old were selected based on the availability of at least 4 hand radiographs taken during at least 20 years of followup, while subjects who were age 60 or older were required to have had at least 4 hand radiographs taken during only 14 years of followup. Individual joints of the hands were graded for the presence and severity of 5 features of OA: osteophytes, joint space narrowing, subchondral sclerosis, lateral deformity, and cortical collapse. They were also graded according to the global Kellgren/Lawrence scale. The incidence and rate of progression of OA, as measured by all scales, increased in progressively older age groups. Cox's proportional hazards models showed that isolated doubtful osteophytes (Kellgren/Lawrence grade 1) and isolated joint space narrowing predicted the development of the radiographic features of OA. The rate of OA progression slowed as the severity increased. We conclude that, in men, the incidence of radiographic features of hand OA increases with age. Regardless of age, the earliest radiographic signs of OA are joint space narrowing and doubtful osteophytes.

High-resolution NMR imaging of an antigen-induced arthritis in the rabbit knee

High-resolution, serial, spin-echo images were obtained for an antigen-induced knee arthritis in six rabbits. The animals were imaged prior to intra-articular challenge and at various time points up to 14 weeks after challenge. Extensive high-signal inflammatory changes were seen at Day 1 in the lymph node, capsule, and surrounding muscle. The muscle and lymph node response decreased rapidly after the first week. The capsule high-signal area reached a maximum at Day 10, but was still extensive at Day 39. The infrapatellar fat pad was replaced more slowly by high signal and the appearance of high signal in both the tibia and femur was a late change. Terminal histological examination showed that the capsule and fat pad high-signal areas corresponded to fibrous and synovial proliferation. The bone changes were a result of edema and cyst formation. The separation of the various time courses of the inflammatory changes may be of value in understanding the model and evaluating potential anti-arthritic drugs.

Production of catabolin by synovium from an experimental model of osteoarthritis

Catabolic factors from synovium, or catabolins, may be important in the pathogenesis of osteoarthritis. The synovial production of catabolin in osteoarthritis was studied using the experimental model of osteoarthritis induced by section of the anterior cruciate ligament. At 1, 4, and 32 weeks after operation, the synovium was harvested, cultured, and the synovial conditioned medium assayed for catabolic activity. The synovial conditioned medium from the operated joints was significantly more capable of inducing cartilage destruction (p less than 0.05) than was the synovial conditioned medium from the unoperated knees. However, when the results were expressed relative to the weight of synovium, the differences were not significant. These results suggest that the increased production of catabolic synovial factors in early experimental osteoarthritis is probably a result of the synovial hypertrophy.

Identification of cartilage matrix glycoprotein in synovial fluid in human osteoarthritis

Cartilage matrix glycoprotein (CMGP) is a high molecular weight protein found in hyaline cartilage and fibrocartilage. It consists of disulfide-bonded subunits, each with an apparent molecular weight of 116,000. Fragmentation of CMGP is noted in extracts of osteoarthritic canine cartilage. CMGP has been identified in the serum and synovial fluid of dogs with experimentally induced osteoarthritis. It has now been identified in synovial fluid from osteoarthritic human joints but not in synovial fluid from joints of patients with other arthritides or joint abnormalities. The possible significance of CMGP in synovial fluid in human osteoarthritis is discussed.