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The Achilles tendon is commonly affected by both chronic repetitive overuse and traumatic injuries. Achilles tendon injuries can potentially affect any individual but have a particularly high incidence in professional athletes. Appropriate imaging evaluation and diagnosis are paramount to guiding appropriate management. In this AJR Expert Panel Narrative Review, we discuss the role of various imaging modalities (particularly ultrasound and MRI) in the assessment of Achilles tendon pathology, focusing on the modalities' relative advantages and technical considerations. We describe the most common diagnoses affecting the Achilles tendon and adjacent structures, highlighting key imaging findings and providing representative examples. Various image-guided interventions that may be used in the management of Achilles tendon pathology are also reviewed, including high-volume injection, tendon fenestration, prolotherapy, and corticosteroid injection. The limited evidence supporting such interventions are summarized, noting an overall paucity of large-scale studies showing benefit. Finally, a series of consensus statements by the panel on imaging and image-guided intervention for Achilles tendon pathology are provided.

BACKGROUND. After rotator cuff tear, properties of the torn muscle predict failed surgical repair. OBJECTIVE. The purpose of our study was to explore the utility of preoperative shear-wave elastography (SWE) measurements of the supraspinatus muscle to predict successful rotator cuff repair, including comparison with MRI-based measures. METHODS. This prospective study included 74 patients (37 men, 37 women; mean age, 63.9 ± 10.0 [SD] years) who underwent rotator cuff repair between May 2019 and January 2021. Patients underwent preoperative clinical shoulder MRI and investigational shoulder ultrasound including SWE using shear modulus. The mean elasticity values of the supraspinatus and trapezius muscles were measured, and the elasticity ratio (i.e., ratio of mean elasticity of supraspinatus muscle to mean elasticity of trapezius muscle) was calculated. The muscular fatty infiltration score (1-3 scale) was recorded on gray-scale ultrasound. On MRI, muscular fatty infiltration was assessed by Goutallier grade (0-4 scale), and muscular atrophy was assessed by the occupation ratio (ratio of cross-sectional areas of supraspinatus muscle and supraspinatus fossa) and by the muscle atrophy grade (0-3 scale). After rotator cuff repair, the surgeon classified procedures as achieving sufficient ( n = 60) or insufficient ( n = 14) repair. RESULTS. Patients with insufficient repair, versus those with sufficient repair, more commonly exhibited a large (3-5 cm) tear (100.0% vs 50.0%). Patients with insufficient, versus sufficient, repair exhibited higher mean Goutallier grade (3.8 ± 0.4 vs 1.9 ± 1.1), mean muscle atrophy grade (2.0 ± 0.8 vs 0.5 ± 0.7), mean supraspinatus elasticity (44.15 ± 8.06 vs 30.84 ± 7.89 kPa), mean elasticity ratio (3.66 ± 0.66 vs 1.83 ± 0.58), and mean gray-scale fatty infiltration grade (2.86 ± 0.36 vs 1.63 ± 0.66) and showed lower mean occupation ratio (0.3 ± 0.1 vs 0.6 ± 0.1) (all, p < .001). AUC for predicting insufficient repair was 0.945 for Goutallier grade, 0.961 for occupation ratio, 0.900 for muscle atrophy grade, 0.874 for mean elasticity, 0.971 for elasticity ratio, and 0.912 for gray-scale fatty infiltration grade. Elasticity ratio (cutoff ≥ 2.51) achieved sensitivity of 100.0% and specificity of 90.0% for insufficient repair. At multivariable analysis including tear size, the three MRI measures, elasticity ratio, and gray-scale fatty infiltration grade, the only independent predictors of insufficient repair were muscle atrophy grade of 2-3 (odds ratio [OR] = 9.3) and elasticity ratio (OR = 15.7). CONCLUSION. SWE-derived elasticity is higher in patients with insufficient rotator cuff repair; the elasticity ratio predicts insufficient repair independent of tear size and muscle characteristics. CLINICAL IMPACT. Preoperative SWE may serve as a prognostic marker in patients with rotator cuff tear.

Objective: The objective of our study was to assess the prevalence and evolution of intrameniscal signal-intensity alteration in subjects with an anterior cruciate ligament (ACL) tear over 24 months and compare clinical outcome and changes of cartilage between subjects with and those without this meniscal abnormality., Materials and Methods: Fifty-seven subjects with an ACL tear were screened for intrameniscal signal-intensity alteration. Morphologic and compositional MRI was performed before ACL reconstruction and 12 and 24 months after ACL reconstruction. Twelve subjects with an intrameniscal signal-intensity alteration and 12 subjects without any meniscal abnormality on MRI were identified. Clinical outcome was measured using the Knee Injury and Osteoarthritis Outcome Score (KOOS), and T1ρ and T2 maps of the cartilage were obtained., Results: In 10 of 12 subjects (83%) the meniscal signal-intensity abnormality identified on baseline MRI was located at the posterior horn of the medial meniscus. None of these subjects presented with a meniscal tear over 24 months of follow-up. At 12 months after the ACL tear, the intrameniscal signal-intensity alteration detected on baseline MRI had completely resolved in seven of 12 subjects (58%), showed a signal-intensity decrease in four (33%), and remained stable in one subject (8%). Of the 10 subjects who underwent MRI at 24 months, the meniscal signal-intensity alteration had completely resolved in eight (80%), and the signal intensity had decreased in the other two subjects. Changes in the KOOS and cartilage T1ρ and T2 values from baseline and 24 months did not differ significantly between subjects with and those without intrameniscal signal-intensity alteration (p > 0.05)., Conclusion: High intrameniscal signal-intensity alterations are a common finding in subjects with an ACL tear and have a benign course over 24 months after surgical repair of the ACL tear.

Objective: The objectives of our study were to determine the accuracy of new MRI criteria in detecting tears of the superficial deltoid ligament of the ankle, the accuracy of established criteria for detecting deep deltoid ligament tears, the most common location of super-ficial deltoid ligament tears, and the frequency of other injuries associated with deltoid tears., Materials and Methods: A chart review yielded 89 cases over a 3-year interval in which ankle MRI was followed by open or arthroscopic surgery and the surgical report described findings in the deltoid ligament. One case was excluded because the MRI study was technically inadequate. MRI and surgical reports were then compared for the presence and location of deltoid ligament tears., Results: MRI findings of focal detachment of the superficial deltoid origin or detachment of the fascial sleeve of the medial malleolus yielded a sensitivity for superficial deltoid ligament tears of 83.3% (45/54) and specificity of 93.9% (31/33). Eight of nine prospectively missed tears were visible on retrospective review. All superficial deltoid tears involved the origin of the ligament from the medial malleolus, and six involved mid or distal bundles of the superficial deltoid as well. MRI findings of discontinuity or nonvisualization of discrete fibers yielded a sensitivity for deep deltoid ligament tears of 96.3% (26/27) and specificity of 97.9% (46/47)., Conclusion: MRI has a high accuracy for deltoid ligament tears in consecutive cases prospectively evaluated by musculoskeletal radiologists. The location of superficial deltoid ligament tears differed in our series from findings previously reported in the imaging literature.

Objective: MR arthrography of the elbow has been found to be useful in the diagnosis of fullversus partial-thickness tears of the collateral ligaments. This article assesses the accuracy of 3-T MR arthrography of the elbow versus conventional 3-T MRI of the elbow, compared with surgery., Materials and Methods: Seventy-nine consecutive conventional elbow MRI and MR arthrography examinations performed on the same patients who went on to surgery were retrospectively read in consensus by two musculoskeletal radiologists. Full- or partial-thickness tears of the collateral ligaments and full-thickness tears of the extensor and flexor tendons were assessed., Results: In 54 patients, the diagnoses made on MRI and MR arthrogram examinations were the same. In 16 patients, MR arthrogram examinations revealed additional findings that were not clearly seen on conventional MRI examinations. There were six full-thickness extensor tendon tears, seven radial collateral ligament tears, and three partial-thickness ulnar collateral ligament tears seen on MR arthrography that were not well seen on conventional MRI. In nine patients, MR arthrogram showed ligaments and tendons to be intact that appeared torn on conventional MRI. There were six ulnar collateral ligaments and three common flexor tendons found to be intact on MR arthrography examination that appeared to be torn on conventional MRI. All MR arthrography findings were confirmed at surgery., Conclusion: MR arthrography is more accurate than conventional MRI of the elbow at 3 T. In 16 cases, MR arthrography showed tendons and ligaments to be torn that appeared intact on conventional MRI. In nine cases, MR arthrography showed intact tendons and ligaments that appeared to be torn on conventional MRI. These nine cases are most likely the result of the tears healing, with fibrous tissue allowing the tendon and ligament tissues to coapt.

Objective: An anterior cruciate ligament (ACL) injury is an increasingly recognized cause of knee pain in young patients and in athletes in particular and can be detected non-invasively with MRI. Anecdotal information suggests that patella alta may be more common in the setting of this injury, but no study has documented this phenomenon. This study sought to test whether an ACL tear is associated with an increased Insall-Salvati ratio suggestive of patella alta., Materials and Methods: Measurements of patellar height, patellar tendon length, and the Insall-Salvati ratio obtained from MRI of the knee were compared for 34 children with an arthroscopically proven ACL tear (mean age ± SD, 12.4 ± 1.4 years) and 36 control subjects with normal knee examinations (12.8 ± 2.1 years); these measurements were performed independently by two observers., Results: Patellar tendon length (47.6 ± 6.6 mm vs 40.4 ± 5.7 mm) and patellar position calculated as the Insall-Salvati ratio (1.16 ± 0.16 vs 0.99 ± 0.14) were significantly greater in the knees with an ACL injury than in those without an internal injury, respectively, on MRI (p < 0.001). Patella length was not significantly different between the two groups (patients vs control subjects, 41.1 ± 4.2 mm vs 40.6 ± 2.7 mm, respectively; p = 0.523). There was good to excellent interobserver and intraobserver correlation for all measurements., Conclusion: There is a significant association between an ACL tear and increased patellar tendon length with a greater Insall-Salvati ratio. The mechanism for this finding is unclear, but this association provides support to suggest relative patella alta may be a risk factor for ACL injuries in pediatric patients.

Objective: The purpose of this study was to characterize meniscal ossicles and their association with meniscal root tears., Materials and Methods: A two-center retrospective assessment of 65 knee MRI studies with meniscal ossicles was performed. The relationship of the ossicle to the meniscal root and horn was assessed along with other findings of internal derangement of the knee., Results: Meniscal ossicles were identified in patients ranging from 23 to 80 years old. The ossicles were located within the posterior horn and root of the medial meniscus in 57 of 65 (88%) examinations. Associated meniscal tears were seen at the site or adjacent to the ossicle in all but one examination (98%). Meniscal extrusion was present in 52% (34/65) of examinations. Associated findings included articular cartilage loss, which was severe in 51% (33/65) of examinations. Anterior cruciate ligament injury or prior anterior cruciate ligament reconstruction surgery was also identified in 58% (38/65) of examinations., Conclusion: Our findings show that the vast majority of meniscal ossicles are associated with posterior horn or meniscal root tears and a high incidence of focal articular cartilage loss as well as anterior cruciate ligament tears.

Objective: The objective of our study was to retrospectively compare the MRI characteristics of surgically confirmed healed and unhealed peripheral vertical meniscal tears., Materials and Methods: The study group consisted of 64 patients with 86 peripheral vertical meniscal tears diagnosed on MRI who subsequently underwent knee surgery. The MRI examinations were retrospectively reviewed to assess the following tear characteristics: tear location relative to the meniscocapsular junction, tear width, tear length, tear extension through one or both surfaces, sequences on which tear was visualized, signal intensity of tear on T2-weighted imaging, and presence of low-signal-intensity strands bridging the tear on T2-weighted imaging. Multivariate logistic regression models were used to determine whether MRI characteristics could be used to distinguish between healed and unhealed tears at surgery., Results: Tear location was the most significant characteristic (p<0.001) for distinguishing between healed and unhealed tears: 17 of 18 (94.4%) tears located at the meniscocapsular junction of the medial meniscus were healed and 15 of 68 (22.1%) tears not located at the meniscocapsular junction were healed. For tears not located at the meniscocapsular junction, MRI characteristics significantly associated with healed tears included a tear width of less than 2 mm (p=0.01), tear visualized only on intermediate-weighted imaging (p=0.01), tear showing intermediate or bright signal intensity on T2-weighted imaging (p=0.06), and low-signal-intensity strands bridging the tear on T2-weighted imaging (p<0.001)., Conclusion: Most peripheral vertical tears at the meniscocapsular junction of the medial meniscus spontaneously heal. The MRI characteristics of tears not located at the meniscocapsular junction can help distinguish between healed and unhealed tears.

Objective: The purpose of this study was to prospectively explore the MRI features of normal healing of the expected residual tendon gap in the Achilles tendon after percutaneous surgical repair., Subjects and Methods: MR images of the Achilles tendon were obtained approximately 4, 8, and 12 weeks after surgery. Assessment of MR images was focused on the presence of residual tendon gap and gap length, Achilles tendon contour, and contrast enhancement in the ruptured area. Cases of open surgical repair were used for comparison. We attempted to statistically compare the timing of tendon gap disappearance within the percutaneous surgical repair group and between the percutaneous and open surgical repair groups., Results: A total of 30 tendons repaired with percutaneous surgical technique and 10 repaired with open surgical technique were evaluated. At the first, second, and third MRI sessions of the percutaneous surgical repair group, a residual gap was found in 100%, 80%, and none of the tendons on T1-weighted images and in 87%, 63%, and none of the tendons on T2-weighted images. Achilles tendon contour was visualized in 30%, 90%, and 100% of the tendons on T1-weighted images and 90%, 100%, and 100% of the tendons on T2-weighted images. Intratendinous enhancement was present in 100%, 73%, and 7% of the tendons in the percutaneous surgical repair group. Ring-shaped peritendinous enhancement was recognized at the third session in all subjects. A significantly longer time was required for tendon gap disappearance after percutaneous than after open surgical repair., Conclusion: The time course of the MR findings in the ruptured Achilles tendon after percutaneous surgical repair appears to reflect regular healing.

Objective: The objective of this study is to report the MR appearance of quadratus femoris muscle tear, another cause of hip pain. We will review the pertinent anatomy of the quadratus femoris muscle, summarize the current literature on quadratus femoris muscle tear, and report our experience in the diagnosis of quadratus femoris muscle tear on MRI., Conclusion: MRI is an important tool in assisting clinicians to make a correct diagnosis for the patient who presents with hip pain. Although quadratus femoris muscle tear is an uncommon injury, radiologists should be aware of this entity to assist with making a diagnosis that is usually unsuspected clinically.

Objective: The objective of this study was to image the Achilles tendon with MR imaging at the magic angle (the long axis of the tendon at 55 degrees relative to the direction of the main static magnetic field [B(0)]) to detect signal from the tendon, to measure the T1 of the tendon, and to determine patterns of contrast enhancement in control subjects and patients., Conclusion: Mean T1 values of 311 +/- 30 msec (at 1.0 T) were found in six volunteers. In six control volunteers, slow uptake of contrast material that dispersed over 40 min-1.5 hr was shown without focal change, with elimination in most cases occurring within 18-24 hr. Small rapidly enhancing focal areas of enhancement were seen next to the insertion of the tendon and centrally within 5-10 min in two control volunteers. The focal areas were located at the sites of the blood supply. A patient with chronic tendinopathy showed early local contrast enhancement that extended widely within the tendon over several hours. Two patients with a partially ruptured or repaired tendon showed marked rapid contrast enhancement. The enhancement was obvious with the tendon at the magic angle but was not evident with the tendon in the usual orientation for MR examinations parallel to B(0).