Tendo Achilles region:
Prone with legs on the edge of the couch
Tendon is followed from its gastrocnemius and soleus origin to insertion to calcaneus
Short axis - elliptical, flattens near insertion; AP diameter 5-6mm; flat/cancave anterior (deep) margin and any convexity is pathological
No synovial sheath and hence no physiological fluid in it and hence any fluid is pathological
Paratenon is seen as 2 echogenic lines
Plantaris tendon lies deep and medial to Achilles (in 20% blends with Achilles medial margin)
Kager's fat pad traingle lies deep to the tendon
Retorcalcaneal bursa: deep to the tendon
Retroachilles bursa: small and usually not visible normally
Peroneal compartment:
Posterior to lateral malleolus
Peroneus brevis is deep to peroneus longus, the former more commonly injured than the latter
Up to 3mm of fluid with the peroneal sheath is normal just below the fibula
P longus inserts into medial cuneiform and 1st MT
P brevis inserts into 1st MT
P quartus is accessory mucle, medial and superficial to the 2 tendons; seen in 10%; commonly inserts into calcaneus
P digiti minimi extends from P brevis to insert into PP of 5th toe
P tertius lies anterior to lateral malleolus and is not a muscle of peroneal compartment; closely related to extensor digitorum longus; inserts into 5th MT
TDH group (invertors):
Tebialis posterior runs immediately posterior to medial malleolus and anterior most of TDH group; inserts into navicular; 4-6mm in diameter; Up to 4mm fluid around it; has a parallel course
Flexor Digitorum longus is smaller than tibialis anterior
Flexor Hallucis longus is smallest; contains minimal fluid in synovial sheath
Accessory flexor digitorum longus may be seen adjacent to hallucis longus
Extensor group:
Pathology is rare in these tendons
From medial to lateral: Tibialis anterior, extensor hallucis longus, extenbsor digitorum longus
Small fluid up to 3mm is normal within these tendon sheaths
In the midfoot, these 3 tendons are superfial. Deep tendons from medial to lateral are extsnor hallucis brevis and extensor digitorum brevis
Hindfoot:
Plantar fascia is tendinous aponeurosis
Fibrillary echogenic structure
Normal thickness 4-4.5mm
Difficult to appreciate on short axis, on longitudinal axis apperas striated
In fascitis, thickening is seen in proximal and medial region at calcaneal attachment
Ankle joint:
Lateral aspect:
85% sprains involve lateral collateral ligaments, which are CFL, anterior TFL, posterior TFL
Anterior TFL: runs horizontally from anterior border of fibular tip to talus; 2.5 cm long and 2mm wide; disruption is seen as hypoechoic mass inferior to fibular
CFL: deep to peroneal tendons; apex of lateral malleolus to tubercle on lateral aspect of calcaneus
References:
McNally EG. Practical musculoskeletal ultrasound. Churchill Livingstone 2005
