Knee effusions, radiology and acute knee trauma

Traumatic knee injury: correlation of radiographic effusion size with the presence of internal derangement on magnetic resonance imaging

PURPOSE

Traumatic knee injury is a common clinical presentation. However, knee internal derangement often goes undiagnosed on physical exam. The authors hypothesize that patients with suprapatellar joint effusion greater than 10 mm anteroposterior diameter on lateral radiograph have a high likelihood of knee internal derangement on magnetic resonance imaging.

MATERIALS AND METHODS

A retrospective review of knee radiographs and magnetic resonance imaging in 198 patients age 18-40 years with acute knee injury was performed. Suprapatellar effusion diameter on lateral radiography was correlated to the presence of internal derangement on magnetic resonance imaging. Magnetic resonance imaging anteroposterior effusion size at four locations was correlated to radiographic suprapatellar effusion measurements.

RESULTS

Logistic regression showed a positive correlation between radiographic effusion size and the presence of internal derangement on magnetic resonance exams (p value < 0.001). Radiographic effusion > 10 mm was established as a positive test, yielding test sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 55, 96, 93, 71, and 77%, respectively. Statistical analysis showed the radiographic anteroposterior effusion diameter most closely approximated the magnetic resonance effusion diameter at the lateral patellofemoral recess.

CONCLUSIONS

This study shows that knee radiography is a highly specific screening test for internal derangement in patients less than 40 years old with acute knee injury. In this patient population, knee effusion > 10 mm on lateral radiograph should prompt consideration for knee magnetic resonance examination. Adopting this approach as a clinical guideline has the potential to decrease delayed diagnosis, improve patient outcomes, and decrease cost-associated disability.

MRI of the knees in asymptomatic adolescent soccer players: A case-control study

PURPOSE

To determine the range of asymptomatic abnormal findings in adolescent soccer players at 3.0T MRI of the knee.

MATERIALS AND METHODS

In all, 87 knees of asymptomatic 14-17-year-old male adolescents were evaluated at 3T, using a standardized examination protocol comprising four sequences: two fat-suppressed T₂ -weighted fast spin-echo sequences (T₂ FSE), in the sagittal (repetition time / echo time [TR/TE], 5.300/71, echo train length [ETL] 17) and coronal planes (TR/TE, 4234/70, ETL 17), one fat-suppressed proton density (PD) sequence in the axial plane (TR/TE, 2.467/40, ETL 9), and one T₁ -weighted spin-echo (T₁ SE) sequence in the sagittal plane (TR/TE, 684/12.5). Soccer players (46 knees) were paired with controls (41 knees) by age and weight. Bone marrow, articular cartilage, meniscus, tendons, ligaments, fat pad abnormalities, and joint fluid were assessed.

RESULTS

One or more abnormalities were detected in 31 knees (67.4%) in the soccer player group, compared to 20 knees (48.8%) in the control group. The prevalence of bone marrow edema was higher in the soccer group (19 knees, 41.3%) than in the control group (3 knees, 7.3%), P = 0.001. Other abnormalities found in this sample (joint effusion, cartilage lesions, tendinopathy, ganglion cysts, and infrapatellar fat pat edema) were not significantly different between the two study groups.

CONCLUSION

Asymptomatic adolescents had a high prevalence of abnormal findings on knee imaging, especially bone marrow edema. This prevalence was higher among soccer players.

LEVEL OF EVIDENCE

4 J. Magn. Reson. Imaging 2017;45:59-65.

ACR appropriateness criteria(®) acute trauma to the knee

There are more than 1 million visits to the ER annually in the United States for acute knee trauma. Many of these are twisting injuries in young patients who can walk and bear weight, and emergent radiography is not required. Several clinical decision rules have been devised that can considerably reduce the number of radiographic studies ordered without missing a clinically significant fracture. Although fractures are seen on only 5% of emergency department knee radiographs, 86% of knee fractures result from blunt trauma. In patients with falls or twisting injuries who have focal tenderness, effusion, or inability to bear weight, radiography should be the first imaging study performed. If radiography shows no fracture, MRI is best for evaluating for a suspected meniscal or ligament tear or patellar dislocation. Patients with knee dislocation should undergo radiography and MRI, as well as fluoroscopic angiography, CT angiography, or MR angiography. The ACR Appropriateness Criteria(®) are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

MRI of the knee joint in asymptomatic adolescent soccer players: a controlled study

OBJECTIVE

The knee is the joint that is most frequently injured in boys 12-15 years old who practice soccer, and MRI is an accurate method of diagnosing sports-related injuries. The objective of this cross-sectional case-control study was to evaluate the knees of asymptomatic adolescent soccer players using open MRI.

SUBJECTS AND METHODS

We evaluated 56 knees of 28 asymptomatic male adolescents 14-15 years old. Participants were divided into two groups and paired by age and weight: soccer players (28 knees) and control subjects (28 knees). All the examinations were performed using a 0.35-T open-field MRI unit and were evaluated by two experienced radiologists blinded to study groups. Bone marrow signal, articular cartilage, meniscus, and fat pad abnormalities and the amount of fluid were assessed.

RESULTS

In the group of soccer players, 18 knees (64.3%) had one or more MRI abnormalities, whereas in the control group nine knees (32.1%) had at least one MRI abnormality (p = 0.03). The prevalence of bone marrow edema was much greater in the group of soccer players (14 knees, 50%), whereas the same abnormality was found in only one knee (3.6%) in the control group (p = 0.0001). Other abnormalities that were not statistically significant with regard to study group were also found in the two groups: infrapatellar fat pad edema, popliteal cysts, and ganglion cysts.

CONCLUSION

Bone marrow edema is a prevalent abnormal finding on MRI scans of knees of asymptomatic adolescent soccer players. MRI findings should be interpreted cautiously and in close correlation with clinical findings.

A screening method for knee trauma

RATIONALE AND OBJECTIVES

The authors performed this study to evaluate whether any one conventional radiographic view is sufficient as a screening method in the detection of acute knee trauma.

MATERIALS AND METHODS

The authors prospectively assessed the efficacy of a single conventional radiograph of the knee in the detection of signs of knee fractures in 214 consecutive adults with acute knee trauma. The evaluated efficacy parameters included specificity, sensitivity, negative predictive value (NPV), and positive predictive value. The percentage reduction in the need for additional conventional radiographs was also calculated.

RESULTS

Fifty-three of the 214 patients (24.8%) had a knee fracture. The sensitivity of the single lateral view in the detection of knee fractures was 100% (95% confidence interval [CI] = 94.3, 100). The lateral view of the traumatized knee was normal in 143 patients (66.8%). The probability of not having a fracture if the lateral view was normal (NPV) was also 100% (95% CI = 97.9, 100). The need for additional radiographs was reduced 67%.

CONCLUSION

A single lateral view as a screening tool for knee fractures has a very high sensitivity and NPV. Because more than 65% of the patients had a normal lateral view in this study, there can be a considerable amount of savings in terms of radiology services for these patients.