Review of Extensor Mechanism Injuries in the Dislocated Knee.

Knee dislocations, aka multiligamentous injuries, are uncommon but devastating injuries often following high-energy trauma. Tears of the major knee stabilizers are well documented; however, injuries of the knee extensor mechanism are less commonly reported. The extensor mechanism is comprised of the patella, patellar tendon, and quadriceps tendons. Magnetic resonance imaging (MRI) is the preferred imaging modality of internal derangements of the knee due to its excellent soft tissue contrast. In this article, we will discuss the normal imaging findings of the extensor mechanism and review abnormalities following knee dislocation.

The Lateral Knee Radiograph: A Detailed Review.

Initial imaging evaluation for a variety of knee pathologies often begins with a radiographic series. Depending on the specific indication, this will include at least two different projections of the knee. In most cases, these are the anteroposterior and lateral radiographs of the affected knee, and sometimes with the contralateral knee for comparison. Typically, knee pathologies visible on lateral view can also be appreciated on the anteroposterior view. However, several pathologic processes occur in anatomic locations typically obscured on other projections because of superimposed osseous structures. Examples of these pathologies include injuries involving the quadriceps or patellar tendons, avulsion fractures involving anterior or posterior structures, and many soft-tissue injuries. Knowledge of the relevant anatomy and typical pathologies typically visualized on the lateral radiograph of the knee is imperative to avoid overlooking these disease processes.

Imaging of Noncontact Anterior Cruciate Ligament Injuries and Associated Bone Marrow Contusion Patterns.

Anterior cruciate ligament (ACL) tears are commonly associated with bone contusions. Bone contusions can lend important insight into increased risk for more subtle concurrent injuries based on common injury mechanisms and patterns, as higher energy trauma has been tied to patterns of specific bone contusions and concomitant injuries. Lateral compartment contusions are most common and occur in pivot shift injuries. Medial compartment contusions may represent a contrecoup mechanism after the initial lateral injuries. Patellotibial contusions require axial loading but are also typically seen in conjunction with lateral and medial compartment contusions. The differences in ACL injury mechanics and physiology as shown by imaging contusion patterns can help clinicians better identify and treat the concurrent associated injuries.

Imaging Review of the Posterior Cruciate Ligament.

Posterior cruciate ligament (PCL) injuries can often be missed on physical examination, especially in multiligament knee injuries. Therefore, a comprehensive approach to imaging the PCL should be implemented whenever history and examination findings indicate relative risk. Radiography, including a posterior-stress view, and magnetic resonance imaging, when available, provide consistently accurate diagnosis of PCL pathology and common knee comorbidities. Computed tomography and ultrasonography can be useful modalities with potential advantages with respect to availability and access, specific comorbidities, and/or cost-effectiveness.

The deep medial femoral sulcus sign: does it exist?

OBJECTIVE: To determine the normal depth of the medial femoral sulcus on lateral radiographs of the knee and determine if abnormal deepening of the medial femoral sulcus exists as a radiographic indicator of intra-articular knee abnormalities. MATERIALS AND METHODS: A retrospective search was performed over a period of 10 years to identify all individuals with a bone contusion of the anterior medial femoral condyle at MR imaging. Study patients had documented acute knee injuries and radiographs 6 weeks or less prior to their MR. A control group had normal MR exams and radiographs 6 weeks or less prior to their MR. Two fellowship-trained musculoskeletal radiologists independently measured the depth of the medial femoral sulcus on lateral radiographs blinded to control or study individuals. RESULTS: The study group consisted of 76 patients (57 men, 19 women; age range, 18-50 years; mean age, 27 years) and 92 control patients (33 men, 59 women; age range, 18-46 years; mean age 26 years). Sulcus depth was (0-2.3 mm reader 1 and 0-1.7 mm reader 2 for controls; 0-2.2 mm reader1 and 0-1.8 mm reader 2 for study patients). No significant difference in sulcus depth was identified between the control and study groups. Inter-reader agreement was very strong. The most common cause of injury in the study group was motor vehicle accidents followed by hyperextension and twisting injuries of the knee. CONCLUSION: The normal medial femoral sulcus ranges in depth from 0 to 2.3 mm. Although impaction of the sulcus does occur following knee injuries, the sulcus does not deepen.

Friction Syndromes of the Knee: The Iliotibial Band and Anterior Fat Pads.

As participation in sporting activities increases among the general population, the incidence of overuse injuries continues to rise. Friction syndromes of the knee are common and are often clinically diagnosed without the need for imaging. However, clinical symptoms may overlap with other joint abnormalities, and physical examination may be limited in individuals with excessive pain. Magnetic resonance imaging has remained the modality of choice for the evaluation of internal derangements of the joints and is a useful aid in the diagnosis of friction syndrome of the knee. This case report provides clinicians with an understanding of the most common friction syndromes of the knee joint as well as their imaging findings. (Journal of Surgical Orthopaedic Advances 27(1):77-80, 2018).

The anteromedial tibial rim sign: an indicator of patellotibial impaction in acute anterior cruciate ligament tears.

OBJECTIVE: We have encountered unexplained anteromedial tibial rim edema in acute anterior cruciate ligament (ACL) tears. Our goal was to determine the incidence, internal derangements, and mechanism of injury in patients with anteromedial tibial rim edema (rim sign). MATERIALS AND METHODS: A retrospective review of ACL tears diagnosed by magnetic resonance imaging over 7 years was performed. Patients were dichotomized into those with and without a rim sign. RESULTS: There were 132 acute ACL tears. Individuals with a rim sign (31, 23%) had more contusions, fractures, ligament tears (P < 0.001), posterolateral corner injuries (P = 0.001), and posterior horn lateral meniscus tears (P = 0.042) than those without. Five individuals demonstrated edema in the inferior patella, consistent with patellotibial impaction. CONCLUSIONS: The rim sign is common in ACL tears, indicating greater internal derangement. The rim sign represents patellotibial impaction with edema rarely present in the patella.

Cysts of the anterior horn lateral meniscus and the ACL: is there a relationship?

OBJECTIVE: Parameniscal cysts have a very high association with meniscal tears in all locations except the anterior horn lateral meniscus (AHLM). The common insertion of the anterior cruciate ligament (ACL) and the AHLM root may provide a pathway for disease. The purpose of our study was to determine if cysts of the ACL are the origin of cysts adjacent to the AHLM. MATERIALS AND METHODS: Radiology reports of all magnetic resonance (MR) examinations of the knee over a 7-year period were searched for "cyst", "ganglion", and "ganglia". Two fellowship-trained musculoskeletal radiologists independently reviewed those MR examinations reported to have a possible cyst of the AHLM and/or the ACL. The study group consisted of those patients with a cyst located adjacent to the AHLM but no meniscal tear of the adjacent meniscus. The ACL in each of these patients was evaluated for the presence of a cyst. Comparison with age- and gender-matched controls was performed. RESULTS: Of 708 cases that contained the word "cyst", "ganglion", or "ganglia", 121 reports indicated a possible cyst of the ACL or AHLM. Twelve individuals had a cyst located adjacent to the AHLM with no meniscal tear. Six (50%) of these individuals had a cyst of the ACL; no ACL cysts were identified in the control group (p = 0.014). Interreader agreement for AHLM parameniscal cysts and AHLM tears was substantial. CONCLUSIONS: Our results suggest that cysts adjacent to the AHLM may in part be explained by cysts or ganglia of the ACL.

The role of imaging in diagnosing diseases of the distal radioulnar joint, triangular fibrocartilage complex, and distal ulna.

OBJECTIVE: The purpose of this article is to review the anatomy, biomechanics, and multimodality imaging findings of common and uncommon distal radioulnar joint (DRUJ), triangular fibrocartilage complex, and distal ulna abnormalities. CONCLUSION: The DRUJ is a common site for acute and chronic injuries and is frequently imaged to evaluate chronic wrist pain, forearm dysfunction, and traumatic forearm injury. Given the complex anatomy of the wrist, the radiologist plays a vital role in the diagnosis of wrist pain and dysfunction.

Patellotibial contusions: a rare cruciate ligament injury pattern.

OBJECTIVE: Patellotibial contusions are a recently described contusion pattern in anterior cruciate ligament (ACL) tears. The purposes or our study were to determine if patellotibial contusions are specific to ACL injuries, determine the internal derangements in patients demonstrating this contusion, and suggest a mechanism of injury. MATERIALS AND METHODS: We conducted a retrospective search of radiology reports over a 6-year period to identify patients with patellar edema described on magnetic resonance (MR) imaging. Only individuals with patellar and tibial edema were included in the study group. These MR examinations were then reviewed for associated internal derangements. RESULTS: From March 2007 to June 2013, 1914 MR examinations of the knee were performed. Two hundred seventy-one reports described patellar edema. Seven individuals had edema of both the inferior pole of the patella and the anterior tibial plateau. Three individuals were involved in motor vehicle accidents (MVAs); 4 patients had a history of an axial load or sports-related injury. All 3 patients involved in MVAs had posterior cruciate ligament tears consistent with posterior translation of the tibia. The non-MVA individuals had tears of the ACL with internal derangements similar to other ACL deficient knees, however, with more widespread osseous contusions. CONCLUSIONS: Patellotibial contusions are high-energy injuries resulting in cruciate ligament tears. These contusions occur exclusively in patients with ACL tears when individuals with a history of direct impaction to the knee are excluded. Axial loading of the extended knee may be an important mechanism of injury in these individuals.

The trochlear cleft: initial experience in elite athletes.

OBJECTIVE: The trochlear cleft is a recently described vertically oriented, low-signal cartilage lesion centered in the trough of the trochlear cartilage. The purpose of our study was to determine the incidence of clefts in an at-risk group of athletes and correlate these findings with clinical and physical examination results. MATERIALS AND METHODS: Sixteen female collegiate volleyball players consented to bilateral knee evaluations, which consisted of history, physical examination, and magnetic resonance (MR) imaging. Two fellowship-trained musculoskeletal radiologists reviewed each MR study by consensus. The trochlear cartilage was considered to be either normal, at risk of developing a cleft, or meeting the previously described criteria for clefts. The Fisher exact test was used for categorical variables, and the Mann-Whitney U test was used for nonparametric continuous variable. RESULTS: A total of 16 athletes (32 knees; 16 women; age range, 18-22 years; mean, 19.9 years) were enrolled in the study. Four knees (13%) in 3 athletes were diagnosed with a trochlear cleft; 6 knees (19%) in 4 athletes had clefts or were at risk of developing clefts. Among those players with unilateral cartilage lesions, 67% had contralateral abnormalities (P = 0.0783). Functional outcomes and physical examination findings were within normal limits for all athletes, with no difference noted between those with and without clefts. CONCLUSIONS: Elite athletes have a much higher incidence of trochlear clefts than the general population and are at risk of bilateral disease. Clefts are likely to be an incidental finding at MR imaging for unrelated symptoms.

Stress injury of the rib in a swimmer.

Rib stress injuries are uncommonly reported but have been documented among athletes, most notably rowers. There have only been two prior case reports of rib stress injuries in swimmers, both of which were young females. Magnetic resonance (MR) imaging was either not obtained or the imaging characteristics were incompletely described. We present a case of an isolated third rib stress injury in a collegiate male swimmer diagnosed via MR imaging. We briefly discuss the possible etiologies for rib stress injuries, their MR appearance, as well as their treatment.

The next accreditation system in radiology: a report from the APDR residency structure committee.

In a move to emphasize the educational outcomes of training programs, the ACGME has created the Next Accreditation System (NAS). The stated goals of NAS include aiding the ACGME in the accreditation of programs based on educational outcome measures, decreasing program burdens associated with the conventional process-based approach to ACGME accreditation, allowing good programs to innovate while enabling struggling programs to steadily improve, and providing public accountability for outcomes. Diagnostic radiology is among the first group of specialties to undergo NAS implementation and began operating under the NAS in July 2013. This article describes the various components of the NAS and explains the new elements, including the clinical learning environment review program, the milestones, the clinical competency committee, and the self-study visits.

Patellotibial contusions in anterior cruciate ligament tears.

Bone contusions are an important ancillary finding of many knee injuries. Not only are they a source of pain, they may suggest a mechanism of injury or a specific derangement of the knee joint. We have encountered a small number of patients being evaluated for anterior cruciate ligament (ACL) tears with unexplained patellar and tibial edema at magnetic resonance (MR) imaging. We present three individuals with contusions of the inferior patella with a corresponding contusion of the anteromedial tibial plateau. Internal derangements in these patients were similar to other individuals with acute ACL tears, however osseous contusions were more widespread. In conclusion, patellotibial contusions are rare and may indicate an injury with forces greater than usually encountered in most ACL tears. A careful search for uncommon associated injuries is prudent in these high-energy knee injuries.