Indian Journal of Rheumatology

REVIEW ARTICLE
Year
: 2018  |  Volume : 13  |  Issue : 5  |  Page : 43--47

Ultrasound of ankle and foot in rheumatology


Amit Kumar Sahu, Prasan Deep Rath, Bharat Aggarwal 
 Departments of Radiodiagnosis and Rheumatology, Max Superspeciality Hospital, New Delhi, India

Correspondence Address:
Dr. Amit Kumar Sahu
Max Superspeciality Hospital, Saket, New Delhi
India

Abstract

Ankle and foot are frequent joints to be involved in arthritis. These joints, being superficial in nature, can be easily accessed by ultrasound. Other advantages of ultrasound are its easy availability, portability, and repeatability. Tenosynovitis, synovitis, tendinosis, bursitis, and enthesopathy are common findings in inflammatory arthritis, which can be easily evaluated by ultrasound. Follow-up and treatment response can also be evaluated with less cost to the patient. High-frequency (7–15 MHz) linear probes with availability of color and power Doppler are ideal for scanning the ankle and foot. Systematic evaluation is the primary requirement for a proper assessment. Ankle is evaluated compartment wise with specific positing for anterior, posterior, medial, and lateral compartments. Foot is evaluated according to the midtarsal joints and metatarsophalangeal and interphalangeal joints. Structured base evaluation of the compartments and joints should be done and the pathologies were noted. Thus, ultrasound of the ankle and foot is a very useful and easily available modality for identifying and distinguishing different rheumatological pathologies such as tendinitis, tenosynovitis, synovitis, bursitis, and enthesopathy of the ankle and foot.



How to cite this article:
Sahu AK, Rath PD, Aggarwal B. Ultrasound of ankle and foot in rheumatology.Indian J Rheumatol 2018;13:43-47


How to cite this URL:
Sahu AK, Rath PD, Aggarwal B. Ultrasound of ankle and foot in rheumatology. Indian J Rheumatol [serial online] 2018 [cited 2021 Mar 6 ];13:43-47
Available from: https://www.indianjrheumatol.com/text.asp?2018/13/5/43/238201


Full Text



 Introduction



Ankle and foot are frequently involved in arthritis, though they are more commonly involved in trauma.[1] Because of the complex anatomy of the soft-tissue structures, it is difficult to assess the distribution and localization of the lesion by clinical examination.[2] The clinical examination may also undermine the pathology in case of subclinical stage or if minimally involved by disease process.[2] Radiography is limited by its information on soft tissue as well as bony involvement. Magnetic resonance imaging though has high resolution is limited by real-time examination, expensiveness, and repeatability. Easy availability, portability, and repeatability are the greatest advantages of ultrasound. Apart from being cost-effective, it also has a high sensitivity for detection of soft-tissue abnormalities of ankle and foot.[3]

 Ultrasonography Imaging Characteristics of the Normal Anatomical Structures



Bony cortex – Hyperechoic and regular with posterior acoustic shadowing [2]Joints – Hypoechoic space between bony cortex and capsule [2]Tendons and Ligaments – Fibrillar pattern on longitudinal scan and punctate pattern on transverse scan [2]Bursae – Usually visualized when distended with fluid and has hyperechoic wall with hypoechoic fluid within them [2]Plantar fascia – Hyperechoic fibrillar bandVessels – Hypoechoic with positive Doppler signalNerves – Fascicular pattern.

 Indications



Rheumatological indications for the ultrasonography (USG) of ankle and foot are:

Joint – Effusion, synovitisTendon – Tenosynovitis, tendinosis, tear, erosion, enthesopathyBursa – BursitisBone – Erosion, osteophytesOthers – Subcutaneous nodules, tophus in gout, ganglion cyst.

 Ultrasound Scanning Technique



High-quality USG machines equipped with 7–15 MHz linear probes with availability of color and power Doppler are ideal for scanning the ankle and foot.[3],[4] A systematic scanning protocol is recommended to assess the important anatomical structures of anterior, medial, lateral, and posterior ankle compartments and the midtarsal and foot joints using multiplanar and dynamic approach. A gel pad should be created on the examined part and the transducer placed gently so as not to create pressure compression on the examined structures. Routine practice of comparing the same structures with contralateral normal side is advisable.

 Anterior Ankle



Ultrasound technique

The patient was seated on examination bed with knee flexed at 45° so that the plantar surface lies flat on the bed. The transducer was kept in axial and longitudinal planes to assess the anterior ankle joint space and the tendons in their full length [Figure 1].{Figure 1}

Anatomy assessed

Anterior tibiotalar joint [Figure 2].Tibialis anterior tendon [Figure 3]Extensor hallucis longus tendonExtensor digitorum longus tendon{Figure 2}{Figure 3}

 Medial Ankle



Ultrasound technique

The patient was seated with plantar surface of the foot rolled internally or in a “frog-leg” position. Alternatively, the patient may lie supine with the foot rotated slightly laterally. Place the short axis of transducer behind the medial malleolus and assess the complete length of the medial compartment tendons [Figure 4].{Figure 4}

Anatomy assessed

Tibialis posterior tendon [Figure 5]Flexor hallucis longus tendon [Figure 5]Flexor digitorum longus tendon [Figure 5].{Figure 5}

 Lateral Ankle



Ultrasound technique

The patient was seated with knee flexed at 45° and the leg slightly tilted medially. Place the short axis of transducer behind the lateral malleolus and assess the complete length of the peroneal tendons [Figure 6].{Figure 6}

Anatomy assessed

Peroneus longus tendon [Figure 7]Peroneus brevis tendon [Figure 7].{Figure 7}

 Posterior Ankle



Ultrasound technique

The patient was in prone position, with the foot hanging freely at the end of the examination bed [Figure 8]. Place the transducer over the Achilles tendon in short axis and assess the full length of the tendon up to the myotendinous junction. Turn the transducer into long axis to assess the tendon attachment to calcaneum.{Figure 8}

Anatomy assessed

Achilles tendon [Figure 9]Kager's fat padPosterior aspects of tibiotalar joint and talocalcaneal jointPlantar fascia.{Figure 9}

 Examination of Foot



Ultrasound technique

The patient position is the same as in assessing the anterior ankle, that is, the patient was seated on examination bed with knee flexed at 45°, so that the plantar surface lies flat on the bed [Figure 10]. Multiplanar assessment of the foot joints is performed by placing the transducer in short axis and long axis.[2]{Figure 10}

Anatomy assessed

Mid tarsal jointsMetatarsophalangeal jointsInterphalangeal joints.

 Pathologies



Joint effusion

Anechoic fluid distension of the joint is compressible by the traducer during dynamic examination.[2],[3] [Figure 11]. Normal amount of fluid is present in the ankle joint. When the anterior–posterior dimension of the fluid pocket in anterior ankle recess is >3 mm, it is pathological.[5]{Figure 11}

Synovitis

When the intra-articular tissue shows soft-tissue thickening, echogenicity and is less compressible or noncompressible.[2] It may show power Doppler signal, suggesting activity.

Tenosynovitis

Thickening of the tendon with decreased echogenicity and loss of normal fibrillar pattern. There may be thickening of the tendon sheath with the presence of surrounding fluid and may also show power Doppler signal [Figure 12] and [Figure 13].[3] {Figure 12}{Figure 13}

Bursitis

Fluid distension of the bursa with or without septations and echogenicity [Figure 14]. Peripheral and internal power Doppler signal may also be exhibited.{Figure 14}

Enthesopathy

Thickening of tendon at its bony attachment with loss of normal fibrillar pattern and decreased echogenicity. There may also be the presence of enthesophytes and power Doppler signal too.

Plantar fasciitis

Thickening of the plantar fascia (>4 mm) at its calcaneal attachment with decreased echogenicity and occasional power Doppler signal [Figure 15].[5]{Figure 15}

Gout

It is commonly seen at the first metatarsophalangeal joint in the form of bone erosions, synovial thickening, echogenic synovium with tophus, and power Doppler signal [Figure 16]. Other joints of the foot and ankle may also be involved.{Figure 16}

 Conclusion



Ultrasound of the ankle and foot is very useful and easily available modality for identifying and distinguishing different rheumatological pathologies such as tendinitis, tenosynovitis, synovitis, bursitis, and enthesopathy of the ankle and foot.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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