Linear signal hyperintensity adjacent to the subchondral bone plate at the knee on T2-weighted fat-saturated sequences: imaging aspects and association with structural lesions

[Bone marrow edema and osteonecrosis in sport : Relevance, prognosis and therapy]

BACKGROUND

Sports activities lead to loading stress for the osteochondral unit of the joints, especially for the lower extremity. Athletes frequently suffer from articular cartilage defects, meniscus and ligament injuries, which are often associated with subchondral bone marrow edema and osteonecrosis.

OBJECTIVES

Presentation of relevance, prognosis and therapeutic options for bone marrow edema and osteonecrosis in sport.

MATERIAL AND METHODS

This review describes the clinical relevance, prognostic aspects and potential treatment options for bone marrow edema and osteonecrosis in athletes.

RESULTS

Subchondral bone marrow edema and osteonecrosis frequently occur in athletes. Most commonly, they are caused by mechanical joint overload due to sporting activities, but they are also found posttraumatically and postoperatively. Their clinical relevance to athletes remains unclear. A stepwise treatment concept includes non-surgical as well as surgical treatment options for symptomatic bone marrow edema and osteonecrosis in sport with different clinical prognoses depending on severity and location of the lesion.

CONCLUSIONS

Bone marrow edema and osteonecrosis may have a relevant impact on the joint function in athletes. They play a decisive role in the rehabilitation following joint injuries and surgeries and are associated with the clinical outcomes following joint injuries and have critical influence on the return to sporting activities.

LEVEL OF EVIDENCE

IV, narrative review.

Subchondral insufficiency fractures, subchondral insufficiency fractures with osteonecrosis, and other apparently spontaneous subchondral bone lesions of the knee-pathogenesis and diagnosis at imaging

Subchondral insufficiency fractures (SIFs) and SIFs with osteonecrosis (SIF-ONs) of the knee (previously misnamed spontaneous osteonecrosis of the knee (SONK)) are bone lesions that appear without prior traumatic, tumoral, or inflammatory event.Both conditions are characterized in the early stages by epiphyseal bone marrow edema (BME)-like signal at MRI. However, while SIFs usually heal spontaneously, they can also evolve to osteonecrosis (i.e., SIF-ON), which may progress to an irreversible collapse of the articular surface. Careful analysis of other MRI signs may help differentiate the two conditions in the early phase. In SIFs, the BME edema-like signal extends to the area immediately adjacent to the subchondral plate, while in SIF-ONs, this subchondral area shows low signal intensity on fluid-sensitive MR images due to altered bone marrow. The thickness and length of subchondral areas with low fluid-sensitive signal intensity are important factors that determine the prognosis of SIF-ONs. If they are thicker than 4 mm or longer than 14 mm, the prognosis is poor. The differential diagnosis of SIFs and SIF-ONs include bone lesions associated with the "complex regional pain syndrome" (CRPS), epiphyseal osteonecrosis of systemic origin, and those related to cartilage pathology.Clinical relevance statement Imaging plays an essential role in diagnosing subchondral insufficiency fractures (SIFs) from subchondral insufficiency fractures with osteonecrosis (SIF-ONs) and collapse, as well as in distinguishing them from other spontaneous knee subchondral bone lesions presenting with bone marrow edema-like signal.Key points• Subchondral insufficiency fractures may affect the knee, especially in older adults.• Subchondral insufficiency fractures usually heal spontaneously.• Sometimes, subchondral osteonecrosis and collapse may complicate subchondral insufficiency fractures.• Bone marrow-like edema is an aspecific sign seen in all these lesions.• Degraded marrow in osteonecrosis complicating fractures is hypointense on fluid-sensitive sequences.

Magnetic Resonance Imaging of Accelerated Bone Remodeling

A regional acceleration of bone remodeling may possibly follow biomechanical insults to the bone. This review assesses the literature and clinical arguments supporting the hypothetical association between accelerated bone remodeling and bone marrow edema (BME)-like signal intensity on magnetic resonance imaging. BME-like signal is defined as a confluent ill-delimited area of bone marrow with a moderate decrease in signal intensity on fat-sensitive sequences and a high signal intensity on fat-suppressed fluid-sensitive sequences. In addition to this confluent pattern, a linear subcortical pattern and a patchy disseminated pattern have also been recognized on fat-suppressed fluid-sensitive sequences. These particular BME-like patterns may remain occult on T1-weighted spin-echo images. We hypothesize that these BME-like patterns, with particular characteristics in terms of distribution and signal, are associated with accelerated bone remodeling. Limitations in recognizing these BME-like patterns are also discussed.

Intra-articular Corticosteroid Injections in the Hip and Knee: Perhaps Not as Safe as We Thought?

Osteoarthritis (OA) of the hip and knee is among the most common joint disorders. Intra-articular corticosteroid (IACS) injections are frequently performed to treat OA and other joint-related pain syndromes; however, there is conflicting evidence on their potential benefit. There is a lack of prospective and large retrospective studies evaluating potential joint findings, including increased risk for accelerated OA progression or adverse joint events, after treatment with IACS injection. Four main adverse joint findings have been structurally observed in patients after IACS injections: accelerated OA progression, subchondral insufficiency fracture, complications of osteonecrosis, and rapid joint destruction, including bone loss. Physicians, including radiologists, should be familiar with imaging findings and patient characteristics that may help them identify potential joints at risk for such events. The purpose of this report is to review the existing literature, describe observed adverse joint events after IACS injections, and provide an outlook on how this may affect clinical practice. Additional research endeavors are urgently needed to better understand and identify risk factors prior to intervention and to detect adverse joint events after injection as early as possible to prevent or minimize complications.

Subchondral Bone and the Osteochondral Unit: Basic Science and Clinical Implications in Sports Medicine

Context:

Articular cartilage injuries and early osteoarthritis are among the most common conditions seen by sports medicine physicians. Nonetheless, treatment options for articular degeneration are limited once the osteoarthritic cascade has started. Intense research is focused on the use of biologics, cartilage regeneration, and transplantation to help maintain and improve cartilage health. An underappreciated component of joint health is the subchondral bone.

Evidence Acquisition:

A comprehensive, nonsystematic review of the published literature was completed via a PubMed/MEDLINE search of the keywords “subchondral” AND “bone” from database inception through December 1, 2016.

Study Design:

Clinical review.

Level of Evidence:

Level 4.

Methods:

Articles collected via the database search were assessed for the association of bone marrow lesions and osteoarthritis, cartilage regeneration, and ligamentous and meniscal injury; the clinical disorder known as painful bone marrow edema syndrome; and the subchondral bone as a target for medical and surgical intervention.

Results:

A complex interplay exists between the articular cartilage of the knee and its underlying subchondral bone. The role of subchondral bone in the knee is intimately related to the outcomes from cartilage restoration procedures, ligamentous injury, meniscal pathology, and osteoarthritis. However, subchondral bone is often neglected when it should be viewed as a critical element of the osteochondral unit and a key player in joint health.

Conclusion:

Continued explorations into the intricacies of subchondral bone marrow abnormalities and implications for the advent of procedures such as subchondroplasty will inform further research efforts on how interventions aimed at the subchondral bone may provide durable options for knee joint preservation.

Subchondral linear hyperintensity of the femoral head: MR imaging findings and associations with femoro-acetabular joint pathology

PURPOSE

The goal of this study was to evaluate the associations between linear hyperintensity in the subchondral bone of the femoral head on T2-weighted MR imaging and structural bone lesions.

MATERIAL AND METHODS

The MR imaging examinations of 63 patients (66 hips) that showed a bone marrow edema pattern (BMEP) of the hip were retrospectively evaluated (study group). The study group comprised 43 men and 20 women, with a mean age of 55.3 years±16.9 (SD) (range: 19-84 years). A control group of 61 patients (77 hips) without BMEP of the hip on MR imaging was created. The control group comprised 30 men and 31 women, with a mean age of 53.1 years±15.6 (SD) (range: 25-83 years). The presence of linear abnormalities of the subchondral bone on T2-weighted fat-saturated sequences (TR/TE=4220-4340/42-45ms) was evaluated and MR imaging findings were correlated with structural femoro-acetabular pathology (advanced chondropathy, osteonecrosis, subchondral insufficiency fractures and macroscopic fractures) and with pain duration.

RESULTS

A linear hyperintensity in the subchondral bone on T2-weighted MR imaging was found in 43/66 hips with areas of BMEP (65.1%) and in 3/77 hips without BMEP (3.8%). Subchondral linear hyperintensity was seen in 15/16 (93.7%) hips with a subchondral insufficiency fracture. Among the 16 hips with an ARCO stage III osteonecrosis, 13 (76.9%) presented BMEP associated with a subchondral linear hyperintensity. BMEP was present in 6/8 hips with ARCO stage IV osteonecrosis; however, only two hips (25%) exhibited subchondral linear hyperintensities. Finally, 77.7% of patients with subchondral linear hyperintensities presented with acute or subacute hip pain (P<0.0001).

CONCLUSION

Femoral head subchondral linear hyperintensity on T2-weighted MR imaging is common and is associated with acute subchondral bone damage.

Bone abnormalities of the knee: MRI features

The knee is one of the most studied anatomical structures by magnetic resonance imaging (MRI). Bone abnormalities are very frequently detected, whether or not related to the symptoms for which imaging was indicated. The aim of this pictorial study is to review the most commonly observed bone abnormalities of the knee, bearing in mind that the interpretation of MR images should always take into consideration both clinical and laboratory data, as well as the results of conventional X-ray imaging.