Pictorial essay: USG of lumps and bumps of the foot and ankle

USG is a cost-effective and dynamic way to interrogate superficial lumps and bumps. We present a pictorial review of the USG findings in various “lumps and bumps” of the foot and ankle.


Introduction
The use of musculoskeletal USG has increased tremendously over the last decade.USG is easily accessible and cheap.It helps to evaluate a lump in real time.[3][4][5] Familiarity with normal ultrasound appearances and knowledge of anatomy and pathological conditions are the keys to accurate assessment of normal variants and pathological conditions.The use of color and power Doppler enables one to assess the vascularity of lesions.USG can be used in acute, subacute, and chronic conditions. [6]Comparison with the contralateral foot and ankle can help one to identify normal variants and evaluate a lump.Although ultrasound cannot be a replacement for MRI, we feel that it should be the first line of investigation for a lump or bump in the foot.We present the characteristic USG findings of lumps and bumps of the foot and ankle.

Methodology
USG of the foot and ankle was performed with a highfrequency 13 MHz probe (Philips iU22, Philips Medical Systems, DA Best, The Netherlands).The ankle is scanned via medial, lateral, and dorsal approached with patient in supine position.The patient is positioned prone to evaluate the posterior ankle and the tendo-Achilles complex.Foot is scanned via dorsal and plantar approaches.The lumps and bumps are scanned in the axial and longitudinal planes.
Color and power Doppler are used to assess the vascularity of a lump and the inflammatory response.]7] Passive and active movements of the joints are performed while examining the appropriate tendons; this enables the operator to appreciate subluxation, dislocation, and tears better [Figure 1].
We present the characteristic USG findings of various lumps and bumps of the foot and ankle.

Ganglion
This is seen as a well-defined, anechoic cystic lesion containing debris and lying close to the tendon sheath or joint capsule.Septations are noted in a complex ganglion, with echoes within the cyst.Color and power Doppler may demonstrate mild peripheral vascularity [Figure 2].

Vascular malformation
Vascular malformations are seen as well-defined lesion with mixed echogenicity and tortousity.Color and power Doppler demonstrate intense vascularity [Figure 3].The adjacent tendon and tendon sheaths are normal in appearance.Sometimes, the presence of small speckles of calcification (phleboliths) makes it easier to diagnose.

Bursitis
Anechoic fluid within a normal bursa, with or without increase in bursal wall thickness, is seen in acute bursitis.The wall of the bursa is thickened in chronic bursitis.Hemorrhage within the bursa results in septations and calcification.Color and power Doppler may show increased vascularity.The presence of gas, along with inflammatory changes within the bursa, is suspicious of superadded infection [Figures 4 and 5].

Tenosynovitis
The tendon is enlarged and the tendon sheath is distended due to anechoic fluid.Hyperemia is noted around the tendon and within the synovium on both color and power Doppler [Figure 6].It is advisable to search for associated retrocalcaneal bursitis in patients with Achilles tendinosis. [8]

Tendinopathy
The involved tendon appears enlarged, with loss of echogenicity.Chronic tendinopathy is associated with atrophy of the tendon.Areas of calcification and cystic changes may also be associated with tendinopathy [Figure 7].The inflamed tendon shows localized or diffuse areas of hypoechogenicity with small vessels within. [9]In the leg, the middle third of the Achilles tendon is the usual site of involvement. [10]A rupture of a tendon may also present as a lump. [10]

Tendon subluxation
The flexor, extensor, and peroneal tendons are held in place with retinaculae.Rupture of these retinaculae may result in subluxation or dislocation of tendons.Dynamic USG enables one to interrogate this effectively.A subluxed or

Osteophytes
These appear as areas of hyperechogenicity with posterior acoustic shadowing adjacent to the joints and continuous with the bone surface.Comparison with adjacent joints and irregularity of the joint supports the diagnosis [Figure 8].

Morton neuroma
These are seen as areas with predominantly low echogenicity with minimal or no vascularity.Compression of the metatarsal heads displaces these neuromas.This maneuver helps to identify small neuromas [Figure 9].

Foreign body granuloma
Foreign bodies are seen as hyperechoic areas with or without posterior acoustic enhancement.Small hypoechoic areas, consistent with fluid or granulation tissue, may be seen in the vicinity [Figure 10].

Tumors
Varied appearances are noted in tumors of the foot and ankle.Mixed hypo-and hyperechogenic lesions may

Plantar fibroma
A plantar fibroma is seen as a well-defined hypoechoic area within the plantar fascia [Figure 12].

Accessory bones
These appear as areas of increased echogenicity with posterior acoustic shadowing.Knowledge of the usual anatomical sites of accessory ossicles and sesamoids is essential to make this diagnosis [Figure 13].

Figure 3 (
Figure 1 (A,B): Subluxed peroneal tendons-Transverse USG in neutral position (A) and in dorsiflexion and eversion (B) shows normal position of the peroneal tendons (short arrow) in neutral position with subluxation over the lateral malleolus (long arrow) during dorsiflexion and eversion

Figure 6 (
Figure 6 (A,B): Tenosynovitis.Transverse gray-scale (A) and color Doppler (B) USG shows an edematous tibialis posterior (long arrow) with a small amount of fluid (small arrow in A) in the tendon sheath and increased vascularity on color Doppler

Figure 8 :
Figure 8: Osteophytes.Transverse USG shows osteophytes (small arrows) at the insertion of the Achilles tendon (long arrow)

Figure 11 :Figure 13 :
Figure 11: Schwannoma.Longitudinal USG shows a mixed echogenic lesion (long arrow) in relation to the posterior tibial nerve (small arrows)