Acute tendon injuries

by Pieter Jordaan, Neil Kruger & Ian Koller

Learning Objectives

  1. A penetrating wound associated with a deficit in tendon function should be regarded as an acute injury to either the tendon or nerve supplying the muscle-tendon unit.
  2. Thorough knowledge of anatomy and hand function is essential to recognise these injuries.
  3. All suspected tendon injuries should be referred for specialist review.

Definition and anatomy

Any injury leading to tendon dysfunction should be assessed for a tendon injury. The specific forearm anatomy and function of each tendon will not be discussed here, but it should be revised to understand tendon injuries better. Tendon injuries are broadly divided into extensor and flexor injuries subdivided into zones. Injuries in the proximal forearm that result in tendon dysfunction are more likely to be nerve injuries.

Extensor tendon zones

Flexor tendon zones

Mechanism of injury

In the majority of cases, the mechanism of injury is penetrating trauma. Closed tendon ruptures occur in Mallet finger injuries, acute Boutonniere deformity, EPL rupture in distal radius fractures and extensor tendon ruptures in rheumatoid arthritis.

Differential diagnosis


The diagnosis is made by taking a good history and examining each tendon individually


Patients with penetrating hand or forearm injury will usually present due to the recent trauma. In closed ruptures, patients may give a history of preceding pain, followed by acute worsening pain or feeling of tearing, associated with a sudden loss in function.


Look for the specific area of the laceration which will guide you as to what injuries to expect.

For the extensor tendons, there will be an evident extensor lag (inability to extend the digit fully) or resisted extension will be weak or painful. This can also indicate a partial injury. The tendon injury may be some way from the entrance wound in penetrating trauma. It may even be on the other side, for example, flexor injuries from a dorsal stab that penetrates the interosseous membrane

The Mallet injury (closed extensor rupture of the insertion on the distal phalanx) causes an inability to extend the distal phalanx actively. An acute Boutonniere deformity (closed rupture of the central slip off the base of the middle phalanx) is a rare injury. It is associated with a weak extension of the middle phalanx confirmed with Elson’s test.

For the flexor tendons, each tendon should be examined individually, including FDS and FDP of each finger. Closed flexor ruptures are rare, but can be associated with inflammatory conditions (RA) or following plating of distal radius fractures or can occur as a Jersey finger (a closed injury where the FDP insertion avulses of the base of the distal phalanx). Flexor tendon injuries are often associated with nerve injuries, and these should be actively excluded.

Certain injuries will leave no functional deficit, for example, an injury to palmaris longus or if only a single wrist extensor or flexor has been injured.

Special investigations

You do not need special investigations to diagnose acute tendon injuries. A baseline X-ray should be performed to exclude underlying fractures or retained foreign bodies. If there is doubt about a closed rupture, an ultrasound may be useful.


All suspected tendon injuries should be referred.






Hammert WC, Calfee RP, Bozentka DJ, Boyer MI, 2010. ASSH Manual of Hand Surgery; Lippincott, Williams and Wilkins (Wolters Kluwer); Philadelphia, USA.

Jordaan PW, Watts AC. Acute tendon injuries; Orthopaedics and Trauma 2019; 33(1): 54–61

Miller MD, 2008. Review of Orthopaedics, 5th edition; Elsevier; Philadelphia, USA.

Wolfe SW, Hotchkiss RN, Pederson WC, Kozin SH, Cohen MS, 2017. Green’s Operative Hand Surgery, 7th Edition; Elsevier; Philadelphia, USA.


A 20-year-old male presents with a stab wound to the back of his hand and inability to extend his index finger. What tendon or tendons has he injured?

  1. EPL
  2. EDC to the index finger
  3. EIP
  4. EDC to the index finger and EIP
  5. EDC to the index finger, EIP and ECU

The correct answer is (D), EDC to the index finger and EIP.