MR imaging of the distribution and location of acute hamstring injuries in athletes

OBJECTIVE: Although hamstring injuries are common in athletes, the distribution and location of such injuries have not been well defined. We used MR imaging to determine the frequency of injury by muscle, involvement of one or more muscles, and location of injuries within the musculotendinous unit. SUBJECTS AND METHODS: We performed MR imaging on 15 consecutive college athletes with clinically diagnosed acute hamstring injuries. A hamstring injury was diagnosed and located on MR imaging by identifying high signal intensity within the muscle on T2-weighted images. RESULTS: We found that 10 athletes had injuries of a single muscle with six injuries of the biceps femoris, three of the semitendinosus, and one of the semimembranosus. In an additional five athletes, we found primary injuries of the biceps femoris and secondary injuries of the semitendinosus. The injuries occurred in diverse locations within the muscles including five injuries at the proximal musculotendinous junction, two at the distal musculotendinous junction, four within the proximal half of the muscle belly, and four in the distal half. All eight intramuscular injuries were located at the musculotendinous junction within the muscle. CONCLUSION: The biceps femoris is the most commonly injured hamstring muscle and the semitendinosus is the second most commonly injured. Although hamstring injuries often involve one muscle injured proximally, multiple muscles were involved in 33% of athletes (5/15) and the injuries were distal in 40% of athletes (6/15). All intramuscular injuries occurred at the musculotendinous junction, either at the ends of the muscle or within the muscle belly.     

Rupture of the conjoint tendon at the proximal musculotendinous junction of the biceps femoris long head: a case report

This case report describes a 20-year-old elite-level Australian Rules football player who suffered three unilateral hamstring injuries within a 2 month period. The first two episodes were managed conservatively. Magnetic resonance imaging following the third episode revealed full thickness disruption of the proximal musculotendinous junction of the biceps femoris long head and semitendinosus muscles and the common proximal (conjoint) tendon. The injury was subsequently surgically repaired. At 16 months following surgery, the player had successfully completed a full competitive season of elite-level Australian Rules football symptom free. Follow-up magnetic resonance imaging demonstrated the repaired tendon to be uniformly hypointense in keeping with reparative granulation tissue formation and restoration of normal muscle morphology. These findings are consistent with an intact repair. The case demonstrates that complete functional and radiological resolution is possible following surgical repair of significant hamstring musculotendinous junction tears.     

MR observations of long-term musculotendon remodeling following a hamstring strain injury

Objective  The objective of this study was to use magnetic resonance (MR) imaging to investigate long-term changes in muscle and tendon morphology following a hamstring strain injury. Materials and methods  MR images were obtained from 14 athletes who sustained a clinically diagnosed grade I–II hamstring strain injury between 5 and 23 months prior as well as five healthy controls. Qualitative bilateral comparisons were used to assess the presence of fatty infiltration and changes in morphology that may have arisen as a result of the previous injury. Hamstring muscle and tendon–scar volumes were quantified in both limbs for the biceps femoris long head (BFLH), biceps femoris short head (BFSH), the proximal semimembranosus tendon, and the proximal conjoint biceps femoris and semitendinosus tendon. Differences in muscle and tendon volume between limbs were statistically compared between the previously injured and healthy control subjects. Results  Increased low-intensity signal was present along the musculotendon junction adjacent to the site of presumed prior injury for 11 of the 14 subjects, suggestive of persistent scar tissue. The 13 subjects with biceps femoris injuries displayed a significant decrease in BFLH volume (p < 0.01), often accompanied by an increase in BFSH volume. Two of these subjects also presented with fatty infiltration within the previously injured BFLH. Conclusion  The results of this study provide evidence of long-term musculotendon remodeling following a hamstring strain injury. Additionally, many athletes are likely returning to sport with residual atrophy of the BFLH and/or hypertrophy of the BFSH. It is possible that long-term changes in musculotendon structure following injury alters contraction mechanics during functional movement, such as running and may contribute to reinjury risk.     

Imaging of the hamstrings

The hamstring muscles, located in the posterior thigh, include the biceps femoris, the semimembranosus, and the semitendinosus. The proximal portions of the hamstring muscles are subject to a variety of injuries and pathology. Many of these entities affect the origin of the hamstrings, including the tendinous enthesis, the underlying ischial tuberosity, and the surrounding tissues. Tendinosis and small partial tears at the origin are the result of chronic attrition. They may be accompanied by bursitis or hamstring syndrome. Apophysitis occurs in teenagers prior to complete fusion of the ischial apophysis and results from repeated traction injuries on the apophysis without discrete displacement. Abrupt injury at the origin from forced flexion of the hip results in osseous avulsions of the apophysis in teenagers and proximal tendon ruptures in adults. Other entities affect the muscles distal to the tendon origins. These injuries include strains and partial tears of the musculotendinous junction from acute indirect trauma, delayed onset muscle soreness from overuse of the muscle group without discrete remembered injury, and contusions and myositis ossificans from direct blunt impact. The imaging features of these injuries and pathology are fairly specific and diagnostic, with the exception of some cases of myositis ossificans and chronic ischial avulsions.     

Total proximal tendon avulsion of the rectus femoris muscle

Total proximal avulsions of the quadriceps femoris muscle group are rare injuries. Between the years 2001 and 2004 five patients with a total proximal avulsion of the tendon of the rectus femoris muscle were treated surgically in Mehiläinen Hospital in Turku, Finland. The median age of the patients was 21 years (range, 19–27) and the patients were all men. There were four soccer players and one hurdler. In all cases an avulsion of the proximal tendon of the rectus femoris muscle was confirmed by MRI. All of the patients were operated on and the delay from the injury to surgery ranged from 18 to 102 days. The result of the surgical treatment was rated good in all cases. All of the patients were able to return to their pre‐injury level of activity 5–10 months after surgery. The median follow‐up time was 20 months (range, 9–38). Surgical treatment of a total proximal avulsion of the tendon of the rectus femoris muscle seems to result in return to the pre‐injury activity level in most cases.     

Knee dislocations: a magnetic resonance imaging study correlated with clinical and operative findings

OBJECTIVES: Our objectives were to determine retrospectively the prevalence, patients' demographics, mechanism of injury, combination of torn ligaments, associated intra-articular and extra-articular injuries, fractures, bone bruises, femoral-tibial alignment and neurovascular complications of knee dislocations as evaluated by magnetic resonance (MR) imaging. MATERIALS AND METHODS: From 17,698 consecutive knee examinations by magnetic resonance imaging (MRI) over a 6-year period, 20 patients with knee dislocations were identified. The medical records of these patients were subsequently reviewed for relevant clinical history, management and operative findings. RESULTS: The prevalence of knee dislocations was 0.11% [95% confidence interval (95% CI) 0.06-0.16)]. There were 16 male patients and four female patients, with ages ranging from 15 years to 76 years (mean 31 years). Fifteen patients had low-velocity injuries (75%), of which 11 were amateur sports related and four were from falls. Four patients (20%) had suffered high-velocity trauma (motor vehicle accidents). One patient had no history available. Anatomic alignment was present at imaging in 16 patients (80%). Eighteen patients had three-ligament tears, two had four-ligament tears. The four-ligament tears occurred with low-velocity injuries. The anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) were torn in every patient; the lateral collateral ligament (LCL) was torn in 50%, and the medial collateral ligament (MCL) in 60%. Intra-articular injuries included meniscal tears (five in four patients), fractures (eight in seven patients), bone bruises (15 patients), and patellar retinaculum tears (eight partial, two complete). The most common extra-articular injury was a complete biceps femoris tendon tear (five, 25%). There were two popliteal tendon tears and one iliotibial band tear. One patient had received a vascular injury following a motor vehicle accident (MVA) and had been treated prior to undergoing MRI. Bone bruises (unrelated to fractures), four-ligament tears, biceps femoris tears, and popliteus tendon tears were encountered only in the low-velocity knee dislocations. Twelve were treated surgically, five conservatively, and three had been lost to follow-up. The biceps femoris tendon was repaired in every patient who was treated surgically. CONCLUSIONS: Knee dislocations occurred more commonly in low-velocity injuries than in high-velocity injuries, predominantly affecting amateur athletes. Biceps femoris tendon tears were the most common extra-articular injury requiring surgery. Neurovascular injury (5%) was uncommon. At imaging, femoral-tibial alignment was anatomic in the majority of patients.     

Flexor femoris muscle complex: grading systems used to describe the complete spectrum of injury

The flexor femoris muscle complex (FFMC) is also known as the hamstring muscle complex or commonly as the “hamstrings.” Three muscles comprise this group: the biceps femoris, the semitendinosus, and semimembranosus. The FFMC is one of the most frequent sites of muscle injury. Hamstring injuries are becoming more common secondary to the increase in society's pursuit of high-energy athletic activities and the greater mobility of our active seniors. The biceps femoris is the most commonly injured muscle of the FFMC.     

Decrease of knee flexion torque in patients with ACL reconstruction: combined analysis of the architecture and function of the knee flexor muscles

A decrease of deep knee flexion torque after anterior cruciate ligament (ACL) reconstruction, using a semitendinosus (and gracilis) tendon, has been reported. However, the cause of this weakness remains controversial. Architectural and functional differences in the knee flexor muscles influence this weakness. the fiber length of the semitendinosus, gracilis, semimembranosus, and biceps femoris were directly measured in six human cadavers. The flexion torque and EMG of the hamstrings were measured in both limbs of 16 patients (23±5 years) after ACL reconstruction (12–43 months post-operation), using ipsilateral semitendinosus tendon. Magnetic resonance imagings were taken, over both the thighs of those patients, to measure muscle volume and to confirm a state of semitendinosus tendon regeneration. The position of the musculotendinous junction of the semitendinosus was also analyzed. The fiber length of the semitendinosus and gracilis were three to four times longer than that of the semimembranosus and biceps femoris. The difference of flexion torque between the normal and ACL reconstructed limbs significantly increased as the knee flexion angle increased. The EMG value for the semimembranosus and biceps femoris of both limbs as well as the semitendinosus of the ACL reconstructed limbs, significantly reduced as the knee flexion angle was increased. The volume of the semitendinosus in the reconstructed limb was significantly smaller than in normal limbs. The regeneration of the semitendinosus tendon was confirmed in all subjects, and the musculotendinous junction position of the reconstructed limb in almost all subjects was found in further image from the knee joint space than that for the normal limb. The decrease of deep knee flexion torque, after ACL reconstruction, could be due to the atrophy and shortening of the semitendinosus after its tendon has been harvested, as well as the lack of compensation from the semimembranosus and biceps femoris, due to the architectural differences between the semitendinosus and the semimembranosus and biceps femoris.     

Avulsion of the common hamstring tendon origin in an active duty airman

Hamstring injuries are common in active athletic populations, such as military service members. Ruptures of the hamstring origin from the ischial tuberosity are rare injuries and missed if not considered in the differential diagnosis of ischial pain. Unlike other hamstring injuries, complete hamstring avulsions must be treated surgically. Results of untreated hamstring avulsions are poor. The purpose of this article is to describe the case of an active duty airman who presented for an unrelated complaint and was discovered to have a 5-week-old hamstring avulsion. Surgical repair of the hamstring avulsion 6 weeks after injury yielded an excellent result and return to full duty. Hamstring avulsions recognized early by history and physical examination and diagnostic imaging permits early and effective treatment. Early surgical repair of the tendon to bone can result in return to full duty.     

Practice patterns for the treatment of acute proximal hamstring ruptures

ABSTRACT

Objective: Proximal ischial hamstring avulsion injuries are relatively uncommon. As such, the management of these injuries is often highly variable. Consensus agreement is lacking for the indications for repair, along with the operative technique, and post-operative rehabilitation. The purpose of this study was to survey surgeons who treat proximal hamstring avulsion injuries to identify current trends in the management of this injury.

Methods: After IRB approval, a 46-question cross-sectional survey was distributed using a secure electronic survey portal. The survey sought to determine surgeon experience, diagnostic preferences, treatment patterns, surgical indications/technique, perceived patient outcomes, surgical complications, as well as post-operative management and rehab protocols. Surveys were completed electronically and anonymously, with invitations distributed to members of the American Orthopedic Society for Sports Medicine (AOSSM) and Arthroscopy Association of Canada (AAC).

Results: A total of 108 surgeons who manage proximal hamstring injuries completed the survey. Most respondents (77%) treat one to five of these injuries per year. MRI was the preferred imaging modality to confirm diagnosis. Despite 98% of respondents indicating that there was a role for surgical management of proximal hamstring avulsions, operative treatment was reportedly undertaken in only 50% of cases seen by each respondent. The top three reported surgical indications were: number of tendons involved (most important factor = 42%, second most = 26%, third most = 13%), amount of tendon retraction (28%, 41%, 16%), and patient activity level (16%, 18%, 24%).

Conclusion: Based on the practice patterns of the surgeons who completed the survey, there is continued disparity in the management of proximal hamstring avulsions. A lack of agreement exists with regards to surgical indications, operative technique, and post-operative protocols. Most striking is the rate of non-operative treatment and perceived rate of poor outcomes within this cohort. Future research should focus on objective evaluation of non-operative management, and additional variables involved in surgical treatment and post-operative rehabilitation.     

Proximal hamstring morphology and morphometry in men: an anatomic and MRI investigation

The proximal musculo‐tendinous junction (MTJ) is a common site of hamstring strain injury but the anatomy of this region is not well defined. A morphometric analysis of the proximal MTJs of biceps femoris long head (BFlh), semitendinosus (ST), and semimembranosus (SM) was undertaken from dissection of 10 thighs from five male cadavers and magnetic resonance imaging of 20 thighs of 10 active young men. The length, volume, and cross‐sectional area of the proximal tendon, MTJ and muscle belly, and muscle‐tendon interface area were calculated. In both groups, MTJs were reconstructed three‐dimensionally. The proximal tendons and MTJs were expansive, particularly within SM and BFlh. Morphology varied between muscles although length measurements within individual muscles were similar in cadavers and young men. Semimembranosus had the longest proximal tendon (cadavers: mean 33.6 ± 2.0 cm; young men: mean 31.7 ± 1.6 cm) and MTJ (>20 cm in both groups) and the greatest muscle‐tendon interface area, followed by BFlh and ST. Mean muscle belly volumes were more than three times greater in young men than elderly male cadavers (P < 0.001). These unique morphometric data contribute to a better understanding of hamstring anatomy, an important factor in the pathogenesis of hamstring strain injury.     

Hamstring injury in athletes: using MR imaging measurements to compare extent of muscle injury with amount of time lost from competition

OBJECTIVE: The purpose of this study was to examine relationships between MR imaging measurements of the extent of hamstring injury and the amount of time lost from competition in a group of athletes. SUBJECTS AND METHODS: Thirty-seven athletes with suspected hamstring injury underwent T1 and inversion recovery T2 turbo spin-echo MR imaging in axial and sagittal planes. The presence and dimensions of abnormal focal intra- and extramuscular T2 hyperintensity were independently recorded by two radiologists, and the muscles involved and intramuscular location of injury were noted. The percentage of abnormal cross-sectional muscle area, abnormal muscle volume, and length of extramuscular T2 hyperintensity were measured from T2-weighted images depicting the maximal extent of the injury. Time (days) lost from competition was noted during follow-up. RESULTS: MR imaging detected hamstring muscle and linear extramuscular T2 hyperintensity in 30 (81%) and 25 (68%) of 37 athletes, respectively. The long head of the biceps was the dominant site of injury in 21 cases. The musculotendinous junction was involved in 28 (76%) of 37 cases. A relationship was seen between days lost from competition and percentage of abnormal muscle area (r = 0.63, p = 0.001) and volume of muscle affected (r = 0.46, p = 0.01), but only a trend for linear extramuscular T2 hyperintensity (r = 0.33, p = 0.12) was shown. CONCLUSION: Rehabilitation time was related to MR measurements such as the percentage of abnormal muscle area and approximate volume of muscle injury. Hamstring injury most frequently involved the long head of the biceps femoris muscle, and involvement of the intramuscular tendon was common.     

MR imaging of the elbow.

Of 27 patients who underwent magnetic resonance (MR) imaging of the elbow, 11 underwent elbow arthroscopy and/or an open surgical procedure. Surgical findings were compared with those from MR imaging. Five healthy volunteers also underwent MR imaging to demonstrate anatomic relationships. Transchondral fracture (osteochondritis dissecans) was identified in three of the 11 patients and was proved at surgery. Loose bodies were suspected at MR imaging in the three patients but were found in only two. One complete avulsion of the ulnar collateral ligament (UCL) and four cases of intact, thickened UCLs were identified at MR imaging and surgery. Loose bodies from the olecranon tip were found in three patients at surgery but were seen on MR images in only two. MR imaging depicted olecranal osteophytes in three cases, which were confirmed at surgery. Two complete avulsions of the biceps tendon and one partial triceps tendon tear were identified with MR imaging and proved at surgery. A postoperative soft-tissue infection and a synovial cyst were also seen at MR imaging and surgery. These results suggest that MR imaging is useful in the evaluation of the elbow.     

Association analysis of the ACTN3 R577X polymorphism with passive muscle stiffness and muscle strain injury

Passive muscle stiffness is considered to be a major factor affecting joint flexibility and is thought to relate to the occurrence of muscle strain injury. In skinned muscle fiber experiments, the R577X polymorphism of the α‐actinin‐3 gene (ACTN 3 ) has been associated with passive muscle stiffness. Our primary purpose was to clarify whether the ACTN 3 R577X polymorphism influences passive stiffness of human muscle in vivo. We also examined whether the ACTN 3 R577X polymorphism is associated with the occurrence of hamstring strain injury. Seventy‐six healthy young male subjects were genotyped for the ACTN 3 R577X (rs1815739) polymorphism. Shear modulus (an index of stiffness) of each hamstring muscle (biceps femoris, semitendinosus, and semimembranosus) was assessed using ultrasound shear wave elastography, and history of hamstring strain injury was collected via a questionnaire. The muscle shear moduli of the semitendinosus and semimembranosus were significantly higher in R‐allele (RR  + RX genotype) carriers than in XX genotype carriers, whereas the shear modulus of the biceps femoris did not differ among the ACTN 3 R577X genotypes. Frequency of past hamstring strain injury also did not differ between the 3 genotypes nor between the R‐allele and XX genotype carriers. This study indicates that RR and RX genotypes of the ACTN 3 R577X polymorphism (corresponding to the presence of α‐actinin‐3 in type II muscle fibers) are associated with increased passive muscle stiffness of the human hamstring in vivo. However, this altered mechanical property might not affect the risk of hamstring muscle strain injury.     

Simulation of biceps femoris musculotendon mechanics during the swing phase of sprinting

INTRODUCTION/PURPOSE: Characterization of hamstring mechanics during sprinting is fundamental to understanding musculotendon injury mechanisms. The objective of this study was to use muscle-actuated forward dynamic simulations to investigate musculotendon mechanics of the biceps femoris long head during the swing phase of sprinting. METHODS: We used a three-dimensional linked segment model with 26 Hill-type musculotendon actuators to simulate swing phase dynamics. Muscle excitations were computed that drove the linked segment model to track measured hip and knee motion of an individual sprinting on a treadmill. The simulations were used to investigate the effect of tendon compliance on the excursions and power development of the muscle and tendinous components of the biceps femoris. RESULTS: The biceps femoris musculotendon complex underwent a stretch-shortening cycle over the latter half of swing phase, with the shortening portion occurring in the final 10% of the gait cycle. Biceps femoris excitation increased markedly between 70 and 80% of the gait cycle and continued through the end of swing. Following the onset of excitation, stretch of the muscle component slowed considerably while the tendon lengthened and stored elastic energy. Simulating the sprinting movement with a more compliant tendon increased tendon elastic energy storage, thereby reducing peak muscle stretch and negative muscle work. CONCLUSIONS: Muscle-actuated forward dynamic simulation provides a powerful approach for investigating biomechanical factors that may contribute to the occurrence of hamstring musculotendon injuries.     

Longitudinal study comparing sonographic and MRI assessments of acute and healing hamstring injuries

OBJECTIVE: We compared sonography and MRI for assessing hamstring injuries in professional football players (Australian football) 3 days, 2 weeks, and 6 weeks after an injury and identified imaging characteristics at baseline that may be useful in predicting the time needed for return to competition. MATERIALS AND METHODS: Sixty men who are professional football players presented with suspected acute hamstring strain underwent sonography and MRI within 3 days of injury; those who were injured returned 2 and 6 weeks later for follow-up MRI and sonography. Two radiologists interpreted either the MR images or the sonograms and were blinded to the results of the other technique. The following six parameters were measured at each assessment: the muscle injured, the site of injury within the muscle, the longitudinal injury length (expressed in millimeters), the cross-sectional injured area (expressed as a percentage), and the presence of interand intramuscular hematoma. RESULTS: At baseline, MRI identified abnormalities in 42 (70.0%) of 60 patients, whereas sonography found abnormalities in 45 (75%) of 60. At 2 weeks, 29 (59.2%) of 49 scans showed abnormalities on MRI and 25 (51.0%) of 49 showed abnormalities on sonograms. Of those players who were injured at baseline, 15 (35.7%) of 42 and 10 (22.2%) of 45 still showed abnormal results on scans at 6 weeks on MRI and sonography, respectively. However, all but one player had returned to competition. The biceps femoris was the most commonly injured muscle and the musculotendinous junction was the most common site of injury. Injuries appeared significantly larger on MRI than on sonography at all time points. Our analysis showed that at baseline, the longitudinal length of hamstring tear on MRI had the highest statistical correlation with recovery (r = 0.58, p < 0.0001) and was the best radiologic predictor for return to competition. CONCLUSION: Sonography is as useful as MRI in depicting acute hamstring injuries and because of lower costs may be the preferred imaging technique. However, MRI is more sensitive for follow-up imaging of healing injuries. The longitudinal length of the strain as measured on MRI is a strong predictor for the amount of time needed until an athlete can return to competition.     

Restoration of anterior cruciate ligament-hamstring reflex arc after anterior cruciate ligament reconstruction

It has recently been emphasized that restoration of neuromuscular function contributes to dynamic stability of the anterior cruciate ligament (ACL) reconstructed knee. The existence of an ACL-hamstring reflex arc, one of the protective ligament-muscular pathways, has been revealed in normal human knees. Although reinnervation to the reconstructed ACL has been observed histologically, it remains unclear whether the ACL-hamstring reflex arc is reestablished. This study examined the existence of the ACL-hamstring reflex arc in ACL-reconstructed knees by analyzing the changes in the hamstring EMG elicited by electrical stimulation to the reconstructed ACL. The patellar tendon grafts transplanted as an ACL substitute in three patients were electrically stimulated via a bipolar wire electrode inserted arthroscopically. The surface EMG was monitored from the ipsilateral biceps femoris and semitendinosus. In two of the three patients the significantly increased EMG value of the biceps femoris was detected between 120 and 140 ms after the onset of electrical ACL stimulation. The increased EMG activity detected in the biceps femoris after the stimulation to the patellar tendon graft indicated reestablishment of the ACL-hamstring reflex arc in the ACL-reconstructed knee.     

Changes in hip joint muscle–tendon lengths with mode of locomotion

We have reported that peak hip extension is nearly identical in walking and running, suggesting that anatomical constraints, such as flexor muscle tightness may limit the range of hip extension. To obtain a more mechanistic insight into mobility at the hip and pelvis we examined the lengths of the muscle–tendons units crossing the hip joint. Data defining the three-dimensional kinematics of 26 healthy runners at self-selected walking and running speeds were obtained. These data were used to scale and drive musculoskeletal models using OpenSIM. Muscle–tendon unit (MTU) lengths were calculated for the trailing limb illiacus, rectus femoris, gluteus maximus, and biceps femoris long head and the advancing limb biceps femoris and gluteus maximus. The magnitude and timing of MTU length peaks were each compared between walking and running. The peak length of the right (trailing limb) illiacus MTU, a pure hip flexor, was nearly identical between walking and running, while the maximum length of the rectus femoris MTU, a hip flexor and knee extensor, increased during running. The maximum length of the left (leading limb) biceps femoris was also unchanged between walking and running. Further, the timing of peak illiacus MTU length and peak contralateral biceps femoris MTU length occurred essentially simultaneously during running, at a time during gait when the hamstrings are most vulnerable to stretch injury. This latter finding suggests exploring the role for hip flexor stretching in combination with hamstring stretching to treat and/or prevent running related hamstring injury.     

Sonography and MR imaging of posterior tibial tendinopathy.

OBJECTIVE: The purpose of the study is to describe the appearance of the posterior tibialis tendon on MR imaging and high-resolution sonography with color and power Doppler imaging and to determine whether sonography is as accurate for diagnosing tendinosis as MR imaging. SUBJECTS AND METHODS: Fifteen healthy volunteers and 31 patients (44 tendons) who were clinically suspected of having posterior tibial tendinopathy were prospectively evaluated with MR imaging and sonography. RESULTS: On MR imaging, the normal tendon was elliptic on cross section and showed low signal intensity on all sequences. Minimal peritendinous enhancement and fluid were seen. On sonography, the tendon showed homogeneous longitudinal echogenic fibers. No flow was seen in or around the tendon. Tendinopathy was characterized by enhancement of the tendon on MR imaging (19/44 tendons); intratendinous flow on color Doppler sonography (16/44 tendons); increase in the anteroposterior diameter causing a rounding of the tendon (18/44 tendons); and inhomogeneity of the tendon (16/44 tendons on MR imaging and 21/44 tendons on sonography). Peritendinosis was characterized by peritendinous enhancement on MR imaging (29/44 tendons); flow on color Doppler sonography (20/44 tendons); and increased soft tissue (20/44 tendons on MR imaging and 27/44 tendons on sonography). When compared with MR imaging, the sensitivity and specificity of sonography for diagnosing tendinopathy were 80% and 90%, respectively, and for diagnosing peritendinosis were 90% and 80%. Addition of abnormal size to the structural abnormality criteria did not improve diagnostic ability. CONCLUSION: Sonography can be useful as the initial imaging study in evaluating abnormalities caused by posterior tibial tendinopathy.