April 11, 2024

Achilles tendon anatomy comprises the confluences of fibers from gastrocnemius and soleus which is a strong supporting tendon in erect.


Achilles Tendon
Achilles Tendon

Gastrocnemius and soleus muscle:- Confluence of fibers:- Achilles tendon is strongest and an average of 15 cm in length

Towards its insertion on the posterior tuberosity of the calcaneus, the tendon fibers twist in orientation by 90°

Horse shoe-shaped retro-calcaneal bursa is located deep and proximal to Achilles tendon insertion on Os-Calcis

It lacks a true synovial sheath, instead enveloped by thin membranous paratenon.

An important watershed region of relative hypovascularity exists approximately 2-6 cm proximal to the calcaneal insertion which is commonly involved in the lesion of the Achilles tendon

Blood Supply of the tendon

1. Musculo-tendinous junctions

2. Surrounding connecting tissues

3. Bone tendon units

Vascular supply is disputably precarious in mid-portion of 2-6 cm from the insertion of tendon and skin directly posterior to the tendon is relatively sparely supplied.

Etiology of Achilles tendon rupture

  • Collagen disorders
  • Inflammatory and autoimmune mechanisms
  • Degenerative and repetitive trauma
  • Drugs ( corticosteroids, fluoroquinolones)
  • Exercise-induced hyperthermia
  • Ischemic injury to the tendon
  • Mechanical theory: eccentric loading + inefficient plantaris
Achilles tendon rupture
Achilles tendon rupture


Most specific and sensitive: MRI

Plain X-ray

Loss of posterior border of Kager’s triangle (fat-filled triangular space in front of tendon Achilles) or complete disappearance

Radiology of Achilles Tendon Injury: Toygar sign
Radiology of Achilles Tendon Injury: Kager’s Triangle

Toygar Sign:- Measurement of angle of the posterior skin surface on lateral view: increases to 130°-150°

Radiology of Achilles Tendon Injury: Toygar sign
Radiology of Achilles Tendon Injury: Toygar sign


Myerson’s classification

Type 1 defect: 1-2 cm long

          End to End repair, Post compartment fasciotomy

Type 2 defect: 2-5 cm long

          V-Y lengthening with/out tendon transfer

Type 3 defect: >5 cm long

          Tendon transfer + V-Y advancement  + Augmentation

Acute Tendon Rupture

All eccentric contraction of the gastrocnemius-soleus complex during sudden/violent dorsiflexion of the plantarflexed foot. It generally gets ruptured in the watershed area.

Notice sudden, painful pop or snap in the calf during recreational activity or exercises that lead to immediate pain, weakness, and alteration of gait

Physical Examination

  • Palpable discontinuity/ defect in rupture site
  • Thompson test (+)
  • Detectable weakness in palmer flexion compared to normal

See also: Foot and ankle examination

Treatment Options

Nonoperative treatment

Optimal treatment is both documented in the nonoperative and operative treatment

POP cast immobilization in plantar flexion for 4 weeks

Followed by exchange casting or splinting to keep the ankle immobilized in the neutral position for 4 more weeks

Operative treatment

Open End to End Repair:

  • Krakow’s
  • Bunnell
  • Kessler’s type suture

Augmentation is done by

  • Fascial turndown flaps (gastrocnemius aponeurotic flap)
  • Tendon transfer
  • Allografts/synthetic grafts

Percutaneous/ Mini open technique

Postoperatively non-weight bearing plaster immobilization is applied

Rupture is common in:

  • Native Achilles tendons: Rich in type I collagen
  • Healing tendons: Rich in type III collagens with poorly organized, weaknesses and less resistance to stretch

Chronic/Neglected Tendon rupture

Injury duration (4 – 10 weeks)

Palpable defects are commonly appreciable in acute rupture and are either less apparent or absent due to fibrosis

Thompson weakness test (-)

History of trauma, plantar flexion weakness + antalgic gait


USG:- Hypoechoic area

MRI:- Extend of rupture and condition of tendon stumps

Treatment Options

Non-Operative Management

Rarely indicated especially in such patients:

  1. Without functional deficits
  2. Significant risk of wound complications
  3. Poor surgical candidates

Operative treatment

Primary end-to-end repair is rarely possible due to retracted tendons

Primary repair of achilis tendon
Primary repair of achilis tendon

( if the defect is < 3cm following debridement and is less than 12 weeks old direct repair may be possible)

If tendon gap is >3 cm

  1. Local tissue transfer
  2. Tissue augmentation
  3. Synthetic biomaterials +/- allografts

Local tissue transfer

Flexor hallucis longus (FHL) tendon is used as it is a long, reliable tendon, source stronger than either peroneal or FDL tendons.

FHL is near to FDL tendon making local transfer technically easier

Other option: Peroneus brevis

Tissue augmentation

Medial and lateral aponeurotic fascial turndown flaps can be done

Other sources:

  • Plantaris
  • V-Y advancement of the gastrocnemius-soleus complex aponeurosis
  • Fascia lata grafting

 Synthetics Biomaterials

  • Carbon fibers
  • Composite carbon fibers/ absorbable polymers
  • Polymers type
  • Mesh


Large defect non-amendable to tendon transfer

Role of plantaris muscle in mid-portion Achilles tendinopathy

Origin: Lateral supracondylar ridge

Insertion: Posterior calcaneus via calcaneal tendon

Action: weakly assist gastric in plantar flexing ankle and flexing knee

Runs in the inner part of the entire calf Resistant cases of Achilles tendinopathy are associated with plantaris tendon involvement