AbstractTendonitis and tendon rupture are rare but recognized complications of fluoroquinolone therapy. Most reports of this problem have appeared in the rheumatology and pharmacology literature, and this topic has received little attention in the radiologic literature. We report two cases of fluoroquinolone-induced tendinopathy and describe their magnetic resonance (MR) and sonographic findings. Although Achilles tendinopathy is generally the result of repetitive injury, it is useful to keep other causes in mind. MR or sonographic findings of Achilles tendinopathy in a patient without history of antecedent trauma should prompt the radiologist to consider fluoroquinolone treatment as a possible causative agent

Richardson, Michael L.

Sterne, Gregory M.

Warren, Bill H.

Radiology Case Reports

Elsevier - Publisher Connector 

Imaging Findings in Two Cases of Fluoroquinolone-Induced Achilles Tendinopathy 

Case Report 1
Patient A is a 56 year old active and otherwise healthy 
female who presented to her primary care provider with a 
five day history of  worsening fever, sore throat, cough, and 
rhinorrhea. Medications included atenolol, hydrochlorothi-
azide, potassium, ranitidine, hormone replacement, and 
vitamins.  The patient had no known drug allergies.  The 
patient was prescribed a 10 day course of  500 mg of  oral 
levofloxacin per day and a beta-agonist inhaler.  
On the last day of  her 10 day antibiotic course, the pa-
tient presented to her physician describing a fairly abrupt 
onset of  bilateral Achilles tendon pain, which increased 
with plantar flexion and direct palpation. There was no 
history of  trauma or recent increase in activity.  Strength 
and range of  motion about the ankle were normal.  A di-
agnosis of  bilateral Achilles tendonitis was made and the 
patient prescribed a 10 day course of  the anti-inflammatory 
agent Naprosyn.  The patient was slow to improve, prompt-
ing  magnetic resonance imaging (MRI) of  both lower ex-
tremities.
T1-weighted MRI (Figure 1) obtained 18 days after onset 
of  symptoms demonstrated small foci of  increased signal in 
the medial-posterior margins of  both tendons (R > L), sug-
gestive of  small partial width tears.
Short tau inversion recovery (STIR) images (Figure 2) 
demonstrated moderate fusiform dilatation of  both Achilles 
tendons, most pronounced 6 cm above their calcaneal in-
sertions.  In addition, there was mild diffusely increased 
signal within the retrocalcaneal soft tissues, consistent with 
edema.  
Minimal magnetic susceptibility artifact (not visible on 
the images above) was noted adjacent to sites of  tendon 
injury, likely representing small foci of  associated hemor-
rhage.  Other visualized tendons were within normal limits.  
No bony abnormality was identified, and vascular struc-
tures were normal in appearance.  
Based on clinical history, physical exam, and MRI find-
ings, a diagnosis of  fluoroquinolone-induced tendinopathy 
was made.  Continuing on Naprosyn, the patient’s symp-
toms gradually abated, reaching near complete resolution 
by eleven months.  No further imaging was obtained.
Case Report 2
Patient B is a 38 year old female who presented to the 
emergency room with a three week history of  weight loss, 
increased sputum production, and shortness of  breath.  At 
the time of  presentation, the patient was ten years status 
post bilateral lung transplant for cystic fibrosis and suffered 
from recurrent pulmonary infections. Her medication list 
was long and included immunosupressants SK506, 
Azathioprine, and low dose prednisone (5mg qd).  She had 
RCR Radiology Case Reports | radiology.casereports.net 87 2006:1(3):87-91
Radiology Case Reports
Volume I, Issue 3, 2006
Imaging Findings in Two Cases of  
Fluoroquinolone-Induced Achilles Tendinopathy
Gregory M. Sterne, Michael L. Richardson, Bill H. Warren
Tendonitis and tendon rupture are rare but recognized complications of  fluoroquinolone therapy.  Most 
reports of  this problem have appeared in the rheumatology and pharmacology literature, and this topic 
has received little attention in the radiologic literature.   We report two cases of  fluoroquinolone-induced 
tendinopathy and describe their magnetic resonance (MR) and sonographic findings. Although Achilles 
tendinopathy is generally the result of  repetitive injury, it is useful to keep other causes in mind. MR or 
sonographic findings of  Achilles tendinopathy in a patient without history of  antecedent trauma should 
prompt the radiologist to consider fluoroquinolone treatment as a possible causative agent.   
Citation: Sterne GM, Richardson ML, Warren BH.  Imaging findings in two cases of 
fluoroquinolone-induced achilles tendinopathy. Radiology Case Reports. [Online] 
2006;1:32.
Copyright: © Gregory M. Sterne. This is an open-access article distributed under the 
terms of the Creative Commons Attribution-NonCommercial-NoDerivs 2.5 License, which 
permits reproduction and distribution, provided the original work is properly cited. Com-
mercial use and derivative works are not permitted.
Abbreviations: MR, magnetic resonance, MRI, magnetic resonance imaging, STIR, short 
tau inversion recovery
Gregory M. Sterne, Michael L. Richardon (E-mail: mrich@u.washington.edu), and Bill H. 
Warren are from the University of Washington, Department of Radiology, Seattle, WA, 
United States of America.
DOI: 10.2484/rcr.v1i3.32
Imaging Findings in Two Cases of Fluoroquinolone-Induced Achilles Tendinopathy
RCR Radiology Case Reports | radiology.casereports.net 88  2006:1(3):87-91
Right Left
Figure 1. T1-weighted MRI obtained 18 days after onset of symptoms demonstrates small foci of increased signal in the 
medial-posterior margins of both tendons (R > L), suggestive of small partial width tears.
Figure 2. Short tau inversion recovery (STIR) images obtained 18 days after onset of symptoms demonstrates moderate fusi-
form dilatation of both Achilles tendons, most pronounced 6 cm above their calcaneal insertions.  A focal area of increased 
signal is noted in the right Achilles tendon.
Right Left
no known drug allergies.  Chest x-ray showed no focal infil-
trates.  She was diagnosed with bronchitis and treated with 
albuterol nebulizers and a fourteen day course of  levofloxa-
cin. Approximately two weeks after her final dose, she re-
ported the onset of  bilateral posterior ankle pain which 
inhibited her ambulation.   
Ultrasound performed six weeks after onset of  symptoms 
(Figure 3) demonstrated diffuse thickening of  the Achilles 
tendons bilaterally, without evidence of  rupture.  Meas-
urements were 8.1 mm (AP) x 12.3 mm (transverse) left, 
and 8.8 mm (AP) x 16.8 mm (transverse) right, with normal 
approximately 5.6 +/- 1mm AP and 9.0 +/- 1mm trans-
verse.  In addition, focal thickening was noted slightly 
proximal to both calcaneal insertions (Figure 4).  
Symptoms gradually improved over the next several 
months, although the patient’s overall medical state de-
clined.  She expired from sepsis approximately one year 
after the ultrasound exam shown below. No further imaging 
was obtained.
Discussion
Levofloxacin is a broad spectrum antibiotic and a mem-
ber of  the synthetic fluoroquinolone family, which includes 
ciprofloxacin, pefloxacin, norfloxacin and many others (1).  
These antibiotics are designed to inhibit DNA gyrase and 
topoisomerase IV in bacteria (2). DNA gyrase is a necessary 
enzyme for the replication, transcription, and repair of  
bacterial DNA, while topoisomerase IV is thought to play a 
role in partitioning chromosomal DNA during bacterial cell 
division.
The fluoroquinolones are frequently prescribed for a 
variety of  infections -- most commonly of  the urinary and 
respiratory tract.  A recent study of  fluoroquinolone usage 
in U.S. hospitals found a mean rate of  150 daily doses / 
1000 patient days in hospital (3).  Side effects of  these anti-
biotics are considered infrequent, and include GI irritation, 
skin rash, central and peripheral neurologic disorders, and 
elevation of  serum transaminases.  Rarely, a patient’s 
course may be complicated by tendinopathy, gait distur-
bance, or hematologic abnormalities.
Fluoroquinolone-induced tendinopathy was first reported 
in 1983 by Bailey et al. (4).  By 1994, 25 fluoroquinolone-
associated tendon ruptures had been reported to the FDA, 
with 22 occurring outside the U.S. (5).  In 2003, Khaliq et 
al reviewed 98 case reports of  fluoroquinolone-associated 
tendinopathy.  Although pefloxacin and ciprofloxacin are 
most frequently implicated, tendon injury has been re-
ported with most fluoroquinolones (6).   The incidence of  
fluoroquinolone-induced tendon injury is an otherwise 
healthy population is not well established, but reports sug-
gest that it is low, ranging from 0.14 % to 0.4 % (6).  The 
relative risk for a patient developing Achilles tendinitis fol-
lowing fluoroquinolone therapy is about 3.7 times the risk 
of  a patient not using fluoroquinolones (7).
The risk of  spontaneous tendon rupture in patients tak-
ing fluoroquinolones appears to be increased by steroid 
therapy, hypercholesterolemia, gout, rheumatoid arthritis, 
advanced age, renal dysfunction, long-term dialysis, and 
solid organ transplantation (6, 8-10).  Of  note, two of  these 
risk factors -- chronic steroid use and solid organ transplant 
-- were present in our patient B.  
The Achilles tendon is most commonly affected, with 
involvement of  quadriceps, peroneus brevis, extensor polli-
cis longus, long head of  biceps, rotator cuff  tendons and 
other tendons also reported (6, 11).  Some authors have 
suggested an increased prevalence in males (6, 12).  Fluoro-
quinolone tendinopathy often has an abrupt and spontane-
ous onset, is frequently bilateral, and is accompanied by 
Imaging Findings in Two Cases of Fluoroquinolone-Induced Achilles Tendinopathy
RCR Radiology Case Reports | radiology.casereports.net 89  2006:1(3):87-91
Figure 4.  Sagittal sonographic view of right distal Achilles 
tendon,  showing focal thickening (small arrows) slightly 
proximal to the calcaneal insertion (large arrow). 
Figure 3.  Transverse sonographic image of the right  distal 
Achilles tendon, showing diffuse thickening (cursors). 
tendon swelling (12).   The latency period between the start 
of  treatment and the appearance of  the first symptoms 
ranges from as little as two hours to 510 days, with a me-
dian of  6 days (6, 12, 13). 
The relationship between fluoroquinolone dose and the 
prevalence of  tendinopathy remains unclear.   Most cases 
arise despite adherence to recommended dosages.  One 
study noted Achilles tendon rupture occurring at a lower 
total dosage than tendonitis, suggesting an idiosyncratic 
response to the drug in some patients (8).
When fluoroquinolone tendinopathy is diagnosed 
promptly, slow, gradual healing usually follows drug discon-
tinuation (9).  Recovery times of  three weeks to two months 
have been reported following rest and immobilization, with 
a small percentage requiring surgery (6, 9). 
Diagnosis of  tendinopathy is largely clinical, following 
onset of  pain in the affected tendon.  However, MRI and 
sonography can provide improved localization and charac-
terization of  a lesion.  While sonography is less expensive 
and more widely available, MRI provides more easily re-
producible imaging.  Areas of  mucoid degeneration, as 
were seen in our patient A, appear as transverse or longitu-
dinal foci of  high signal intensity on  T1-  and T2-weighted 
MR images (13, 14).  MRI may be useful in distinguishing 
between tendinitis and partial tendon rupture (15).  MRI 
may also demonstrate additional findings, such as a thick-
ened paratenon, peritendinous fluid, or edema of  peritend-
inous fat (13).  However, these findings are nonspecific, and 
can appear in tendinopathies of  other etiologies.  Sonogra-
phy may demonstrate tendon thickening (similar to that in 
our patient B) and hypoechoic areas within the tendon (13). 
Color Doppler sonography may be useful in distinguishing 
hematoma from acutely torn tendon ends.
In the few cases of  fluoroquinolone-related tendinopathy 
where tissue pathology has been obtained, non-specific 
findings of  necrosis, neovascularity, interstitial edema and 
cystic change have been reported (6).  The pathophysiology 
of  fluoroquinolone-related tendinopathy is not well under-
stood.  Many researchers believe the mechanism of  
fluoroquinolone-related tendon injury to be ischemic in 
nature, aggravated by local mechanical stresses (6).  It has 
also been suggested that fluoroquinolones alter not only 
proteoglycan synthesis, but also cellular function, perhaps 
at the mitochondrial level (16, 17). 
Conclusion
Although Achilles tendinopathy is generally the result of  
repetitive injury, it is useful to keep other causes in mind. 
MR or sonographic findings of  Achilles tendinopathy in a 
patient without history of  antecedent trauma should 
prompt the radiologist to consider fluoroquinolone treat-
ment as a possible causative agent.
References
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Imaging Findings in Two Cases of Fluoroquinolone-Induced Achilles Tendinopathy

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