diagnostic process

Last edited 07/2021 and last reviewed 08/2021

It is important to distinguish a ruptured Achilles tendon from both an incomplete tear of the tendon, and from a tear of the soleus muscle. Up to 25% of ruptures are missed at first presentation and the delay in their treatment may significantly impede subsequent recovery.

Tests for a ruptured Achilles tendon include:

• tiptoe test:
• a patient whom is able to stand on tiptoe on their affected leg is very unlikely to have a ruptured achilles tendon
• other causes of a painful foot or ankle may also prevent standing on tiptoes (i.e. it is a highly sensitive but non-specific test)

• Simmond's squeeze test and Copeland's pressure test are both sensitive tests for Achilles tendon rupture

diagnostic process:

The diagnosis of acute Achilles tendon rupture may be missed by non specialist in 20% of the cases. This may be due to several reasons:

• clinician may think of local bruising (rather than a rupture) based on the patients explanation (kicked or hit on the back of the heel tendon by a ball or racquet)
  
  
• the injury may be considered trivial due to:
• absence of an audible snap on patient history
• absence of pain in around  a third of patients
• mild external bruising and swelling (since  tendon usually ruptures within its paratenon sheath)
• a gap may not be felt in longitudinal tears
• other plantarflexors may mask the weakness from a ruptured Achilles tendon (1,2,3) 

Physical examination

Instruct patient to lie prone on the examination couch with feet hanging over the edge. 

• defect in the Achilles tendon is visible in most of the patients accompanied by swelling due to peritendinous haemotoma
• defect is usually palpable (with a sensitivity of 0.71 and specificity of 0.89)
• specific test for diagnosis include: Simmonds or Thompsons’ test
• Thompsons’ test - muscles of the calf is squeezed gently while the motion of the foot is observed
• in an intact tendon -  the foot planterflexes (negative test)
• false negative can occur in
• when the patient has an intact plantaris tendon
• in the setting of a chronic rupture, where scar tissue and fibrosis of the paratenon can mimic continuity between the gastroc-soleus muscle belly and the calcaneus
• in ruptured tendon - little or no plantar flexion of the foot relative to the contralateral leg (positive test) (1,2)         

Simmonds’ triad (angle of declination, palpation for a gap, and calf squeeze) is the preferred examination method since it yields a more accurate diagnosis when compared to Thomson’s calf squeeze test alone (2).

• look (observe for angle of declination of the foot)
• altered angle of declination (or “angle of dangle”) indicates the loss of tension caused by the ruptured tendon
• when compared to the normal leg, ankle and foot of the affected leg is positioned in a more  dorsiflexed position
• a modified test was introduced by Matels
• patient is instructed  to actively flex the knee through 90° while observing whether the foot of the injured leg falls into a more dorsiflexed position
• this test alone has a sensitivity of 0.88 and a positive predictive value of 0.92
• feel - palpate for the gap
• palpate the tendon along its entire length to identify a gap
• sensitivity is only 0.73 and the positive predictive value is 0.82
• move - calf squeeze
• similar Thomson’s calf squeeze test
• results should be recorded as as “plantarflexion noted” or “plantarflexion not noted” (since “calf squeeze test positive” could mean either positive plantarflexion or positive rupture)
• has a sensitivity of 0.96 and a positive predictive value of 0.98 (2)

Imaging

• usually not required since the condition can be diagnosed clinically
• if diagnosis is unclear (partial rupture or tendinopathy), ultrasonography or MRI may be helpful
• ultrasound:
  • is better than radiography
    • may distinguish:
      • complete rupture
      • partial rupture
      • paratenonitis

It is important that a patient with suspected acute Achilles rupture is referred to an orthopaedic surgeon on the same day rather than requesting investigations which may delay treatment (2).

Note:

• the Simmonds triad is preferred to Thomson’s isolated calf squeeze test
• comparative studies have reported that two of the three tests were positive in all ruptures making the sensitivity 100% for this triad

Reference:

• (1) Gulati V et al. Management of achilles tendon injury: A current concepts systematic review. World J Orthop. 2015;6(4):380-6.
• (2) Singh D. Acute Achilles tendon rupture. BMJ. 2015;351:h4722.
• (3) Pedowitz D, Kirwan G. Achilles tendon ruptures. Curr Rev Musculoskelet Med. 2013;6(4):285-93.