Achilles tendon rupture is a partial or complete tear of the largest and strongest tendon in the body. It most commonly occurs in the hypovascular zone 2-6 cm proximal to the insertion ('critical zone' or 'watershed area'). Most frequent in recreational athletes ('weekend warriors') aged 30-50. Clinical diagnosis is usually straightforward (positive Thompson test, palpable gap), but MRI and US play critical roles in partial tears and chronic cases. On MRI, complete tear shows loss of tendon continuity, retraction, and fluid-filled gap. On US, 'empty tendon bed' finding confirms complete rupture. Surgical repair or functional rehabilitation are standard treatment options for acute complete tears.
Age Range
25-60
Peak Age
40
Gender
Male predominant
Prevalence
Common
The Achilles tendon connects the gastrocnemius and soleus muscles to the calcaneus bone and withstands forces up to 12.5 times body weight. Rupture typically occurs from acute mechanical loading on a background of degenerative tendinopathy. The 'critical zone' 2-6 cm proximal to the insertion is the most vulnerable area because it has the lowest blood supply — the 'watershed area' between vascular territories of the posterior tibial and sural arteries. Degenerative changes: mucoid degeneration, hypoxic degeneration, tendolipomatosis, and calcific tendinopathy weaken collagen structural integrity. In acute rupture, eccentric contraction (plantar flexor activation during dorsiflexion) is the most common mechanism. MRI findings: in complete tear, tendon continuity is lost and fluid + hemorrhage accumulates at the tear site → hyperintense gap on T2. The proximal stump takes on a wavy appearance because the tendon loses its tension. On US, the tendon bed remains empty because the torn ends retract and the gap is filled by fluid/hemorrhage.
On US in complete Achilles tendon rupture, a hypoechoic/anechoic gap is seen at the tear site instead of normal tendon fibrillar structure — the tendon bed appears 'empty.' On dynamic US, independent movement or immobility of tendon ends during dorsiflexion provides functional evidence.
On sagittal T2-weighted and STIR images, complete loss of Achilles tendon continuity is seen. T2 hyperintense fluid/hemorrhage accumulation ('gap sign') is present at the tear site. Proximal and distal tendon ends can be identified; the distance between ends (retraction amount) is critical for surgical planning. If retraction >3 cm, additional graft may be needed for surgical repair.
Report Sentence
The Achilles tendon demonstrates complete discontinuity approximately [x] cm proximal to the insertion with T2 hyperintense fluid accumulation at the tear site; consistent with acute complete Achilles tendon rupture.
In complete rupture, the proximal tendon stump loses its tension and takes on a wavy (serpiginous) morphology. This 'retraction + waviness' pattern is the characteristic MRI finding of complete tear. The proximal stump is pulled superiorly by gastrocnemius/soleus muscle contraction. Retraction amount is measured on sagittal MRI and provides critical information for surgical planning.
Report Sentence
The proximal tendon stump shows wavy morphology and retraction, consistent with complete rupture.
On longitudinal B-mode US, a hypoechoic/anechoic fluid/hemorrhage-filled gap is seen at the complete rupture site instead of normal tendon fibrillar structure — 'empty tendon bed' finding. On transverse sections, tendon cross-section is not visible, replaced by irregular hypoechoic area. On dynamic US, immobility of tendon ends during ankle dorsiflexion is functional evidence of complete tear. US sensitivity for complete tear is reported as 95%+, specificity 95%+.
Report Sentence
On US, tendon continuity is not identified in the critical zone of the Achilles tendon with empty tendon bed finding; consistent with complete rupture.
In partial tear, tendon thickening and intratendinous T2 signal increase are seen on T2-weighted images but tendon continuity is not completely lost — some intact fibers persist. Partial tears are best evaluated on axial images: percentage and location of affected fibers are determined. Partial tears carry risk of progression to complete rupture.
Report Sentence
Intratendinous T2 signal increase and focal thickening are noted in the Achilles tendon with preserved continuity, consistent with partial tear.
On power Doppler US, increased neovascularization is seen in the zone of chronic tendinopathy or healing tear. Normal Achilles tendon is avascular and shows no Doppler signal. Increased vascularity reflects active inflammatory/reparative process and correlates with pain. This finding is helpful in differential diagnosis of chronic tendinopathy and partial tear.
Report Sentence
Intratendinous neovascularization is noted in the Achilles tendon on power Doppler, consistent with active tendinopathy/reparative process.
Criteria
Complete tendon discontinuity, <2 weeks. Trauma history + positive Thompson test.
Distinct Features
MRI: tendon gap filled with acute hemorrhage and fluid. Wavy proximal stump, measurable retraction.
Criteria
Disruption of some tendon fibers with partial preservation of continuity.
Distinct Features
MRI: intratendinous T2 signal increase, thickening but continuity preserved. US: focal hypoechoic area but no empty tendon bed.
Criteria
Complete rupture untreated for >4-6 weeks.
Distinct Features
MRI: scar tissue/granulation between ends, proximal stump muscle atrophy, significant retraction. Surgical repair becomes difficult — graft or tendon transfer may be needed.
Distinguishing Feature
Plantar fasciitis shows fascial thickening and signal increase on the plantar surface of calcaneus, while Achilles rupture involves the posteriorly inserting tendon; different anatomical locations
Distinguishing Feature
Retrocalcaneal bursitis shows fluid-filled bursa anterior to Achilles insertion on T2, while Achilles rupture shows tendon discontinuity and gap sign
Distinguishing Feature
Calcaneal stress fracture shows bone marrow edema and linear fracture line on T1, while Achilles rupture has no bone pathology and tendon structural disruption is predominant
Urgency
urgentManagement
surgicalBiopsy
Not NeededFollow-up
specialist-referralTwo treatment options exist for acute complete Achilles tendon rupture: (1) surgical repair — preferred in young, active patients, lower re-rupture rate (3-5% vs 12-15%), better plantar flexion strength; (2) functional conservative treatment — early controlled motion and progressive weight-bearing protocol, preferred in older/sedentary patients. Conservative treatment is usually sufficient for partial tears. Surgical difficulty increases in chronic tears — V-Y advancement or tendon transfer may be needed.
Complete Achilles tendon tear usually requires surgical repair, especially in active and young patients. Conservative treatment (cast/splint) can be applied in selected patients but re-rupture risk is higher. Partial tears are generally treated conservatively. Early diagnosis and correct classification (complete vs partial, retraction distance) is critical for surgical planning.