Magnetic resonance imaging ofarticular cartilage injuries of the knee

Magnetic resonance imaging (MRI) is a widely available, powerful imaging modality in the United States that has rapidly become a mainstay for evaluation of the musculoskeletal system, largely because of its unparalleled depiction of most osseous and soft-tissue pathology. The application of MRI to detect cartilage injuries has evolved to the point where it is possible to noninvasively diagnose cartilage lesions that previously required an invasive examination, eg, arthrography or arthroscopy. However, successful cartilage imaging requires knowledge of the unique technical considerations and limitations of MRI. In this chapter we review current state-of-the-art knee MRI for three groups of chondral disorders: acute osteochondral fractures, osteochondritis dissecans, and degenerative lesions. The role of MRI in osteochondral fractures includes the demonstration of purely chondral intra-articular fragments and the identification of associated injuries, especially previously unrecognized subchondral bruises. MRI may also play a role in surveillance for osteochondral sequelae after injury. For osteochondritis dissecans, MRI can provide evidence supporting the diagnosis of a loose fragment and may aid in the evaluation of cartilage overlying osteochondral defects. Current MRI techniques can show moderate and severe lesions of chondromalacia and chondrosis. Newer techniques show potential for diagnosing these degenerative conditions at earlier stages when the changes are mild. We review these issues and provide examples showing the MRI appearance of common articular injuries.     

Non-invasive MRI assessment of the articular cartilage in clinical studies and experimental settings

Attrition and eventual loss of articular cartilage are important elements in the pathophysiology of osteoarthritis (OA). Preventing the breakdown of cartilage is believed to be critical to preserve the functional integrity of a joint. Chondral injuries are also common in the knee joint, and many patients benefit from cartilage repair. Magnetic resonance imaging (MRI) and advanced digital post-processing techniques have opened possibilities for in vivo analysis of cartilage morphology, structure, and function in healthy and diseased knee joints. Techniques of semi-quantitative scoring of human knee cartilage pathology and quantitative assessment of human cartilage have been developed. Cartilage thickness and volume have been quantified in humans as well as in small animals. MRI detected cartilage loss has been shown to be more sensitive than radiographs detecting joint space narrowing. It is possible to longitudinally study knee cartilage morphology with enough accuracy to follow the disease-caused changes and also evaluate the therapeutic effects of chondro-protective drugs. There are also several MRI methods that may allow evaluation of the glycosaminoglycan matrix or collagen network of articular cartilage, and may be more sensitive for the detection of early changes. The clinical relevance of these methods is being validated. With the development of new therapies for OA and cartilage injury, MR images will play an important role in the diagnosis, staging, and evaluation of the effectiveness of these therapies.     

MRI of articular cartilage: revisiting current status and future directions

OBJECTIVE: The purpose of this article is to review the current understanding of the MRI appearance of articular cartilage and its relationship to the microscopic and macroscopic structure of articular cartilage, the optimal pulse sequences to be used in imaging, the appearance of both degenerative and traumatic chondral lesions, the appearance of the most common cartilage repair procedures, and future directions and developments in cartilage imaging. CONCLUSION: Articular cartilage plays an essential role in the function of the diarthrodial joints of the body but is frequently the target of degeneration or traumatic injury. The recent development of several surgical procedures that hold the promise of forming repair tissue that is hyaline or hyalinelike cartilage has increased the need for accurate, noninvasive assessment of both native articular cartilage and postoperative repair tissue. MRI is the optimal noninvasive method for assessment of articular cartilage.     

MR imaging of post-traumatic articular cartilage injuries confined to the femoral trochlea. Arthroscopic correlation and clinical significance

OBJECTIVE: To assess and describe post-traumatic articular cartilage injuries isolated to the trochlear groove and provide insight into potential mechanism of injury. MATERIALS AND METHODS: We retrospectively evaluated MR imaging findings of all knee MRIs performed at our institution over the last 2 years (2450). Thirty patients met the criteria of a cartilage injury confined to the trochlear groove. In 15 cases, which were included in our study, arthroscopic correlation was available. Each plane was evaluated and graded for the presence and appearance of articular cartilage defects using a standard arthroscopic grading scheme adapted to MR imaging. Any additional pathological derangement was documented and information about the mechanism of injury was retrieved by chart review. RESULTS: In all cases the cartilaginous injury was well demonstrated on MRI. In 13 patients additional pathological findings could be observed. The most frequently associated injury was a meniscal tear in nine patients. In eight cases, the arthroscopic grading of the trochlear injury matched exactly with the MRI findings. In the remaining seven cases, the discrepancy between MRI and arthroscopy was never higher than one grade. In 13 out of 15 of patients trauma mechanism could be evaluated. Twelve patients suffered an indirect twisting injury and one suffered a direct trauma to their knee. CONCLUSION: The findings of this study demonstrate that MR imaging allows reliable grading of isolated injury to the trochlear groove cartilage and assists in directing surgical diagnosis and treatment. These injuries may be the only hyaline cartilage injury in the knee and meniscal tears are a frequently associated finding. Therefore, it is important to search specifically for cartilage injuries of the trochlear groove in patients with anterior knee pain, even if other coexistent pathology could potentially explain the patient's symptoms.     

Magnetic resonance of the knee menisci and cartilage

This contribution is designed to present magnetic resonance (MR) of the menisci and cartilage to the orthopedic surgeon in a practical manner. The investigators describe those MR sequences and techniques that optimally show injury, as well as the expected morphology of the menisci. Criteria for diagnosis of meniscal tears are outlined. Common “equivocal” meniscal tear appearances are shown and strategies for resolving such equivocal cases are suggested. The difficult problem of diagnosing a meniscal remnant tear or reinjury of a repaired meniscus is covered. Finally, MR imaging of chondromalacia and osteochondral injuries is discussed.     

MR imaging of cartilage repair surgery of the knee

Articular cartilage is a complex tissue with unique properties that are essential for normal joint function. Many processes can result in cartilage injury, ranging from acute trauma to degenerative processes. Articular cartilage lacks vascularity, and therefore most chondral defects do not heal spontaneously and may require surgical repair. A variety of cartilage repair techniques have been developed and include bone marrow stimulation (microfracture), osteochondral autograft transfer system (OATS) or osteochondral allograft transplantation, autologous chondrocyte implantation (ACI), matrix-assisted chondrocyte implantation (MACI), and other newer processed allograft cartilage techniques. Although arthroscopy has long been considered as the gold standard for evaluation of cartilage after cartilage repair, magnetic resonance (MR) imaging is a non-invasive method to assess the repair site and can be scored using Magnetic resonance Observation of Cartilage Repair Tissue (MOCART). MR also provides additional evaluation of the subchondral bone and for other potential causes of knee pain or internal derangement. Conventional MR can be used to evaluate the status of cartilage repair and potential complications. Compositional MR sequences can provide supplementary information about the biochemical contents of the reparative tissue. This article reviews the various types of cartilage repair surgeries and their postoperative MR imaging appearances.     

MR imaging of cartilage repair surgery of the knee

Articular cartilage is a complex tissue with unique properties that are essential for normal joint function. Many processes can result in cartilage injury, ranging from acute trauma to degenerative processes. Articular cartilage lacks vascularity, and therefore most chondral defects do not heal spontaneously and may require surgical repair. A variety of cartilage repair techniques have been developed and include bone marrow stimulation (microfracture), osteochondral autograft transfer system (OATS) or osteochondral allograft transplantation, autologous chondrocyte implantation (ACI), matrix-assisted chondrocyte implantation (MACI), and other newer processed allograft cartilage techniques. Although arthroscopy has long been considered as the gold standard for evaluation of cartilage after cartilage repair, magnetic resonance (MR) imaging is a non-invasive method to assess the repair site and can be scored using Magnetic resonance Observation of Cartilage Repair Tissue (MOCART). MR also provides additional evaluation of the subchondral bone and for other potential causes of knee pain or internal derangement. Conventional MR can be used to evaluate the status of cartilage repair and potential complications. Compositional MR sequences can provide supplementary information about the biochemical contents of the reparative tissue. This article reviews the various types of cartilage repair surgeries and their postoperative MR imaging appearances.     

Advanced morphological and biochemical magnetic resonance imaging of cartilage repair procedures in the knee joint at 3 Tesla

Morphological and biochemical magnetic resonance imaging (MRI) is due to high field MR systems, advanced coil technology, and sophisticated sequence protocols capable of visualizing articular cartilage in vivo with high resolution in clinical applicable scan time. Several conventional two-dimensional (2D) and three-dimensional (3D) approaches show changes in cartilage structure. Furthermore newer isotropic 3D sequences show great promise in improving cartilage imaging and additionally in diagnosing surrounding pathologies within the knee joint. Functional MR approaches are additionally able to provide a specific measure of the composition of cartilage. Cartilage physiology and ultra-structure can be determined, changes in cartilage macromolecules can be detected, and cartilage repair tissue can thus be assessed and potentially differentiated. In cartilage defects and following nonsurgical and surgical cartilage repair, morphological MRI provides the basis for diagnosis and follow-up evaluation, whereas biochemical MRI provides a deeper insight into the composition of cartilage and cartilage repair tissue. A combination of both, together with clinical evaluation, may represent a desirable multimodal approach in the future, also available in routine clinical use.     

Magnetic resonance imaging of knee hyaline cartilage and intraarticular pathology

Injuries to the hyaline cartilage of the knee joint are difficult to diagnose without invasive techniques. Even though these defects may be the most important prognostic factors in assessing knee joint injury, they are usually not diagnosed until arthrotomy or arthroscopy. Once injuries to hyaline cartilage are found and/or treated, no technique exists to follow these over time. Plain radiographs, arthrograms, and even computed tomography fail to detail most hyaline cartilage defects. We used magnetic resonance imaging (MRI) to evaluate five fresh frozen cadaver limbs and 10 patients whose pathology was known from arthrotomy or arthroscopic examination. Using a 0.35 Tesla superconducting magnet and spin-echo imaging technique with a head coil, we found that intraarticular fluid or air helped to delineate hyaline cartilage pathology. The multiplane capability of MRI proved to be excellent in detailing small (3 mm or more) defects on the femoral condyles and patellar surface. Cruciate ligaments were best visualized on sagittal oblique projections while meniscal pathology was best seen on true sagittal and coronal projections. MRI shows great promise in providing a noninvasive technique of evaluating hyaline cartilage defects, their response to treatment, and detailed anatomical information about cruciate ligaments and menisci.     

MRI of pediatric patients: Part 1, normal and abnormal cartilage

OBJECTIVE: Cartilage development has a profound impact on musculoskeletal growth. The objective of this article is to offer insights about the maturation of hyaline cartilage through MRI. We begin by briefly describing the molecular make up of hyaline cartilage. We will then follow with a discussion of the basic principles to apply to optimize hyaline cartilage imaging. The remainder of the article will focus on the MR appearances of the distinct histologic types of hyaline cartilage, normal variations in cartilage development, and the sequelae of cartilage injury on normal skeletal development. CONCLUSION: Knowledge of the normal and abnormal appearances of hyaline cartilage on MRI of pediatric patients will allow readers to avoid mistaking the changes associated with skeletal maturation for pathologic findings.     

Magnetic resonance imaging of cartilage and cartilage repair

Magnetic resonance (MR) imaging of articular cartilage has assumed increased importance because of the prevalence of cartilage injury and degeneration, as well as the development of new surgical and pharmacological techniques to treat damaged cartilage. This article will review relevant aspects of the structure and biochemistry of cartilage that are important for understanding MR imaging of cartilage, describe optimal MR pulse sequences for its evaluation, and review the role of experimental quantitative MR techniques. These MR aspects are applied to clinical scenarios, including traumatic chondral injury, osteoarthritis, inflammatory arthritis, and cartilage repair procedures.     

A practical guide to imaging of cartilage repair with emphasis on bone marrow changes

Orthopedic surgeons have multiple options available to treat articular cartilage lesions, including microfracture, osteochondral autografting, and autologous chondrocyte implantation. By having basic knowledge of these surgical procedures, radiologists can more accurately interpret imaging studies obtained after surgery. In this article, we briefly review the different types of cartilage repair procedures, their appearance on magnetic resonance imaging (MRI), and pathologic MRI findings associated with postoperative complications. We also briefly discuss advanced MRI techniques (T2 mapping, delayed gadolinium-enhanced MRI of cartilage, sodium MRI) that have been recently used to assess the biochemical composition of repair tissue matrix. MRI can accurately assess the status and health of cartilage repair tissue. By providing this information to orthopedic surgeons, radiologists can play a valuable role in the management of patients who undergo cartilage repair surgery.     

Bilateral triradiate cartilage injury: an overuse syndrome in an adolescent football player

The triradiate cartilage is not a recognized site for an overuse injury. We present here X-ray and MRI findings of a young athlete with chronic right-sided hip pain that proved to be secondary to triradiate cartilage overuse injury. MRI also revealed similar but milder findings on the left side. Distal radial and proximal humeral epiphyses, iliac bone, tibial tubercle, calcaneal and proximal 5th metatarsal apophyses are common sites of overuse injuries in the skeletally immature athletes. Radiological findings may resemble a Salter-Harris type I injury, but an insidious onset of the symptoms, absence of acute trauma, and bilaterality of MRI findings may help differentiate these entities.     

The proximal hamstring muscle-tendon-bone unit: A review of the normal anatomy, biomechanics, and pathophysiology

Proximal hamstring injuries occur during eccentric contraction with the hip and the knee on extension; hence they are relatively frequent lesions in specific sports such as water skiing and hurdle jumping. Additionally, the trend toward increasing activity and fitness training in the general population has resulted in similar injuries. Myotendinous strains are more frequent than avulsion injuries. Discrimination between the two types of lesions is relevant for patient management, since the former is treated conservatively and the latter surgically. MRI and Ultrasonography are both well suited techniques for the diagnosis and evaluation of hamstring tendon injuries. Each one has its advantages and disadvantages. The purpose of this article is to provide a comprehensive review of the anatomy and biomechanics of the proximal hamstring muscle-tendon-bone unit and the varied imaging appearances of hamstring injury, which is vital for optimizing patient care. This will enable the musculoskeletal radiologist to contribute accurate and useful information in the treatment of athletes at all levels of participation.     

Transient lateral patellar dislocation: review of imaging findings, patellofemoral anatomy, and treatment options

Transient patellar dislocation is a common sports-related injury in young adults. Although patients often present to the emergency department with acute knee pain and hemarthrosis, spontaneous reduction frequently occurs, and half of cases are unsuspected clinically. Characteristic magnetic resonance imaging (MRI) findings often lead to the diagnosis. The purpose of this review is to illustrate the MRI findings of lateral patellar dislocation and concomitant injuries, such as kissing contusions of the medial patella and lateral femoral condyle; osteochondral and avulsion fractures; and injuries of the medial patellofemoral ligament/retinacular complex. This article will also briefly review patellofemoral anatomy and passive, active, and static stabilizers. Predisposing factors for patellar instability, including trochlear dysplasia, patella alta, and lateralization of the patella or tibial tuberosity and their relevant measurements will also be highlighted. Treatment options, including surgery, such as medial patellofemoral ligament reconstruction, tibial tuberosity transfer, and trochleoplasty, and their postoperative imaging appearances will also be discussed.     

MR imaging of cartilage repair procedures

It is becoming increasingly important for the radiologist to evaluate the appearance and outcome of cartilage repair procedures. MR imaging is currently the best method for such evaluation but it is necessary to use cartilage-specific sequences and to modify those sequences when necessary to minimize artifacts from retained metal within the joint. This article reviews the surgical technique of the more commonly performed cartilage repair procedures, currently recommended techniques for the MR imaging evaluation of articular cartilage and cartilage repair procedures, and the MR imaging appearance of cartilage repair procedures and of the most frequently encountered complications following such procedures.     

MRI evaluation of costal cartilage injuries

OBJECTIVE: The usefulness of MRI in costal cartilage injuries has not been shown. We report the MRI findings in a series of patients with costal cartilage injuries. CONCLUSION: MRI can be a useful technique in the diagnosis of costal cartilage injuries.     

Relevant traumatic injury of the knee joint-MRI follow-up after 7-10 years

Objective

To evaluate prospectively the history of relevant traumatic knee injuries at least 7 years after trauma by MRI focusing on the development of degenerative changes.

Materials and methods

Seventeen patients without baseline degenerative changes had a follow-up knee MRI several years after relevant knee injury (interval baseline—follow-up was 9.1 years, S.D. ±1.3 years). Relevant knee injury was defined as complete cruciate or collateral ligament rupture, traumatic meniscal tear or osteochondral injury. Baseline MRI examinations were evaluated for traumatic ligamentous, chondral, meniscal and osseous lesions. Follow-up MRIs were evaluated for ligamentous and meniscal status, articular surface and incidence of degenerative changes such as cartilage loss, osteophytes and bone marrow lesions.

Results

Among the 11 patients who had a complete rupture of the ACL at baseline, 3 (27.3%) presented with cartilage loss. Among the eight patients who had suffered a post-traumatic meniscal tear at baseline, four (50%) presented with cartilage loss at follow-up. Among the five patients who had an osteochondral fracture at baseline, two (40%) presented with cartilage loss at follow-up imaging. Cartilage loss in all cases was observed adjacent to the subregions where meniscal damage and/or osteochondral incongruence was/were present at follow-up imaging.

Conclusion

We hypothesize that the post-traumatic or postsurgical meniscal damage and the persistence of an irregular articular surface may have played a role in the subsequent loss of cartilage in our patient population.     

Cartilage imaging of the hand and wrist using 3-T MRI

The prevalence of osteoarthritis of the hand and wrist is high, and a thorough assessment of even subtle cartilage injuries is necessary before surgical interventions. Although magnetic resonance imaging (MRI) has been established as an important diagnostic tool for the evaluation of hand and wrist disorders, the focus has been on the assessment of the triangular fibrocartilage complex, tendons, ligaments, and the detection of avascular necrosis or occult fractures rather than on cartilage imaging. 3-T MR systems have become more and more widely available and yield an improved signal-to-noise ratio and thus a higher spatial resolution than 1.5-T systems. In principle, this should be especially beneficial for depicting the thin cartilage layers of the hand and wrist. This review focuses on cartilage imaging of the hand and wrist with 3-T MRI and addresses these four topics: (1) the advantages of 3-T versus 1.5- and 1-T MRI, (2) dedicated sequence protocols at 3 T including novel three-dimensional sequences, (3) imaging findings in common cases of overuse or sports injury, and (4) functional cartilage imaging techniques of the hand and wrist, for instance, delayed gadolinium-enhanced MRI of the cartilage.