The Achilles tendon is the biggest and strongest tendon in the lower leg. It produces plantar, or downward, flexes and movements of the foot and ankle. It’s also responsible for push-off during jumping and other activities. 

The Design of the Tendon

The gastrocnemius muscle (a longer muscle that originates above the knee) and the soleus muscle (a shorter muscle that begins in midcalf) combine to form the Achilles tendon. Additionally, a less important muscle known as the plantaris helps in the movements of the gastrocnemius and soleus muscles. It’s noteworthy that the gastrocnemius soleus mechanism within the Achilles tendon is very strong and can withstand forces up to 9 times body weight. 

The Achilles tendon attaches in the mid posterior (back) of the heel. This broad attachment continues down around to the bottom (plantar) aspect of the heel. It combines there with the attachments coming back from the plantar fascia. Additionally, a small sac (bursa) is present between the back of the superior (top) of the calcaneus and the Achilles tendon as it comes down to attach to the heel. This is called the retrocalcaneal (behind the calcaneus) bursa. This bursa protects the Achilles tendon at the edge of the calcaneus. 

Blood supply to the Achilles tendon comes from the muscle above, the insertion below at the heel attachment and very slightly from fluid around the tendon in the peritenon or tissue around the tendon. Approximately 2 to 5 cm proximal or above the attachment of the Achilles is an area of the Achilles where the blood supply is the poorest. This area is known as the critical zone and is a site of frequent Achilles tendon injury, poor healing, and rupture.

Tendon Injury and Symptoms

Achilles tendon rupture or injury is not infrequent. Sometimes patients will describe a several month history of discomfort and swelling in the critical zone area prior to rupture. This may be the result of a prior partial injury or chronic Achilles tendinopathy. (See chronic Achilles Tendinopathy.)

A common mechanism of injury is a sudden, forced dorsiflexion (upward force) on the foot and ankle. This may result from stepping a hole, landing on the leg with the ankle dorsiflexed, or having several other players fall on the back of the leg and producing the dorsiflexion. 

Another common mechanism of injury is sudden explosive forward acceleration with weight on the leg, producing a tear. Suddenly stepping back and placing full weight on the leg (as in racquet sports) can also produce a tear. 

The patient will usually complain of immediate sharp severe pain. Patients often describe "being hit in the back of the leg or shot in the back of the leg". There may be immediate swelling, bruising and discomfort with weight-bearing. The patient can usually still walk to some degree. However there may be difficulty in going up and down steps. 

Other tendons, such as the flexor tendons (FHL, FDL and PTT) also produce ankle flexion and may allow continued function. Unfortunately, up to 25% Achilles tendon ruptures are missed or neglected and present late for diagnosis.

Tendon Diagnosis and Treatment

Treatment of an acute Achilles tendon rupture begins with obtaining a medical history and undergoing careful examination, where the doctor will check for various signs of distress:

  • There will usually be swelling, tenderness and bruising in the area of the tear. 
  • There may be a palpable gap or divot due to retraction of the portion of the Achilles tendon attached to the muscle. 
  • The patient will usually still be able to flex the ankle up and down due to the secondary muscles noted above. 
  • The Thompson Doherty test may be positive. (In this test the patient lies prone, the injured foot hanging over the end of the bed, and the calf muscle is gently squeezed by the examiner. Normally this will cause the foot to flex. In cases of a complete Achilles rupture, the foot is not attached and will not move.)
  • An x-ray may be obtained to rule out rupture of the Achilles with a portion of its bony attachment. 
  • An MRI may be obtained to determine the degree of rupture in the amount of retraction.

In the United States, the usual treatment of an acute Achilles tendon tear is surgical repair. Despite some mostly Scandinavian and European literature describing success with conservative treatment, multiple studies have shown improved results with surgical repair. 

Restoring the muscle-tendon unit of the Achilles tendon to its original length improves overall muscle strength recovery. Closing the gap between the ends of the torn tendon also reduces the amount that is replaced by scar tissue and reduces the re-tear rate to 4% (from 8 to 10% for conservative treatment). 

Complications from surgical treatment denounced in the European literature have been significantly reduced with modern techniques of repair. Conservative treatment is still used in cases where the patient is to medically fill to undergo surgical repair, requires minimal ability to ambulate, or cannot comply with the necessary rehabilitation.

Surgical repair of the Achilles tendon is usually performed as an outpatient procedure with general, spinal, or block anesthesia. 

  • A longitudinal incision is made on the back of the Achilles tendon. 
  • The peritenon around the tendon is opened and the tear is exposed. Tears in the mid-tendon at the critical zone (most common) have multiple strands of tendon on both ends and resemble a "mop head" or “spaghetti”.
  • Both ends of the tendon are repaired with a strong central or core suture, and a smaller peripheral suture brings everything together. 
  • The peritenon and then skin is closed.

Surgical risks with an Achilles tendon tear and repair are anesthesia-related risks, wound healing problems or infection, re-tear of the tendon, or irritation or injury to the small sural nerve next to the tendon resulting in numbness or irritation of the nerve.

Recovery

After surgery, the patient is placed in a protective boot and ordered to obey no weight bearing guidelines for 6 weeks. Depending on the exact nature of the tear and repair, gentle active range of motion may be begun at two weeks after surgery. 

Generally, at 6 weeks after surgery, protected weight-bearing in the boot and therapy for strengthening, balance, and proprioception are begun. At 10 weeks post surgery, weight-bearing in a shoe will be initiated if the Achilles strength is 70% to 75% of the opposite side. Later, sports specific exercises will be initiated. 

Our team has also been using platelet plasma (PRP) to improve wound healing and tendon healing for our Achilles tendon repairs.  

Information on Similar Injuries

  • Occasionally the Achilles tendon may be avulsed or tear off of the calcaneus with or without a fragment of the calcaneus. In this case, a small piece of calcaneus may be excised and the tendon repaired to the bone directly with the use of small anchors. A larger piece of calcaneus may be reattached with screws. The postoperative treatment is the same. Tendon to bone healing is somewhat superior to tendon to tendon healing.
  • Occasionally an Achilles tendon tear may be mimicked by tearing of the plantaris tendon, adjacent to the Achilles tendon. The history, symptoms, and exam may be similar. The main Achilles tendon is still intact, however. MRI is sometimes helpful in confirming one injury versus the other. Treatment, in this case, is usually conservative if the main Achilles tendon is still intact. 
  • The gastrocnemius soleus complex may also tear or be injured more proximally (higher) in the muscle or at the junction between the muscle and tendon. These are usually treated conservatively with protection and therapy. Careful examination and MRI may be required for the diagnosis.

Information on Chronic Injury

Chronic Achilles tendon ruptures (i.e. greater than two months old) may require a different approach in care. An MRI is first obtained to evaluate the tendon tear. Usually, there is a significant gap between the ends of the tendons. The proximal portion of the tendon attached to the muscle becomes scarred down with time and may not be attachable to the other portion, even after the muscle-tendon unit is freed up (tenolysis) at the time of surgery. In this case, other techniques are required to close the gap and reconstruct the tendon. 

A portion of the tendon may be folded down to close the gap; the tendon may be lengthened (V-Y flap); or a tendon transfer may be performed using the plantaris tendon (if present) or the FHL tendon of the great toe. Artificial tendon grafts may be ordered, and strips of tissue from the patient's thigh (fascia lata) may be used to augment the repair. 

Each injury case is customized. I do not favor using artificial tendon grafts secondary to problems with increased scar formation, rejection, and infection. These surgeries are also performed as an outpatient with general, spinal or block anesthesia. The postoperative course is similar, although rehabilitation is more conservative.