Achilles Tendon Rupture: Causes and a Post-Surgery Training Framework

Achilles tendon rupture refers to a complete tear of the Achilles tendon, usually occurring in the zone 2 to 6 cm above where it inserts on the calcaneus, an area with poorer blood supply. The condition may be associated with prior tendon degeneration and micro-injury.

It is common in men aged 30 to 40 and mainly happens during exercise, especially among people who are only occasionally active, often called weekend warrior athletes, and most often during soccer, racquet sports, or basketball. Statistically, these injuries may be misdiagnosed as an ankle sprain in about 20% of patients.

Epidemiology

• More than 75% of Achilles tendon ruptures occur in patients aged 30 to 40
• The incidence is higher in men than in women, with a male-to-female ratio ranging from 1.7:1 to 19:1
• Left Achilles tendon rupture occurs more often than right, thought to be because right-dominant individuals typically push off with the left foot during exercise
• Incidence among athletes is: runners 7% to 18%, dancers 9%, gymnasts 5%, tennis players 2%, and American football players under 1%. Achilles disorders affect roughly 1 million athletes each year

Pathophysiology

• The Achilles tendon is the largest tendon in the body, designed to withstand loads up to 10 times body weight
• It is formed by the fused tendons of the gastrocnemius and soleus, whose tendinous ends insert on the calcaneus to form the Achilles tendon
• A healthy tendon is composed mainly of about 90% type I collagen. After a tendon rupture, marked changes occur, involving the breakdown of type I collagen fibers and an increase in type III collagen, which resists tensile strength less well; this pathological change causes a previously healthy tendon to lose its biomechanical properties
• In the early healing phase, inflammatory cells along with neutrophils and macrophages infiltrate the rupture site, and in the later recovery phase, fibroblasts responsible for producing collagen proliferate within the tendon tissue
• The blood supply to the Achilles tendon comes from the musculotendinous junction and the osseotendinous insertion, with external supply from a thin layer of loose connective tissue, the paratenon; the zone 2 to 6 cm above the calcaneal insertion has a poorer blood supply
• Before reaching the calcaneal insertion, the Achilles tendon rotates internally, creating torque in the tendon structure, which is thought to potentially reduce blood supply and thereby increase the risk of tendon rupture

Risk factors

• Diseases: connective tissue disorders, seronegative spondyloarthropathy, rheumatoid arthritis, collagen vascular disease, diabetes, gout, hyperparathyroidism, renal insufficiency, hypothyroidism
• Medications: anabolic steroids, long-term oral corticosteroids, and quinolone antibiotics, which cause collagen fiber degradation and reduce Achilles tendon strength
• Lifestyle: low activity or prolonged inactivity, a sedentary lifestyle, prolonged immobilization
• Increasing age: with age, the tendon’s resilience and strength decline
• A history of Achilles tendinitis or tendinopathy, even without any history of injection treatment
• Mechanical imbalance, such as reduced flexibility of the gastrocnemius-soleus complex
• Body weight: obesity increases the load on the Achilles tendon
• Genetic predisposition: may be associated with HLA-B27 or blood type O

History

• Patients typically report feeling as if the back of the heel was kicked or struck, though nothing actually contacted it
• They may hear or feel a pop or tearing sensation
• Pain may be present, especially on weight-bearing
• Patients may subsequently have hindfoot stiffness or weakness, with chronic Achilles tendinitis

Physical examination

• In an acute complete Achilles tendon rupture, tenderness and a palpable defect can usually be felt at the back of the ankle
• Swelling or bruising may be visible
• Hatchet strike defect: on palpation 2 to 6 cm above the Achilles tendon insertion, there is tenderness and a defect
• Positive Thompson test: diagnoses Achilles tendon rupture, with a sensitivity of 0.96 and a specificity of 0.93
• If the Achilles tendon is only partially torn, patients may still be able to perform some plantar flexion, because other muscles such as the tibialis posterior, plantaris, peroneus longus, and peroneus brevis assist the movement

Diagnostic tools

• Routine X-ray examination can rule out a calcaneal avulsion fracture, which is usually seen on a lateral foot-and-ankle X-ray

• Ultrasound (US) and magnetic resonance imaging (MRI) are used when the diagnosis of complete rupture is in doubt or a partial tear is being considered; they make little difference to overall management strategy, and ultrasound is more immediate, has sufficient diagnostic capability, and can also assess the medial and lateral portions of the tendon as well as surrounding structures

• In an acute Achilles tendon rupture, the proximal and distal ends of the tendon do not appear continuous on long-axis ultrasound; a defect is seen in the image of the fibrillar tendon, extending between the superficial and deep borders of the tendon

• When ultrasound measures the gap between the ruptured tendon ends, the foot position and degree of plantar flexion must be recorded. The range typically runs from maximal tolerable plantar flexion (usually between 10 degrees and 45 degrees) to the neutral position the patient can perform and/or tolerate

• A tendon gap of 10 mm is often used as the minimum threshold above which surgery is considered. A gap of more than 15 mm between the tendon ends is thought to increase the re-rupture rate

• For post-operative or post-treatment follow-up, ultrasound is very important, for example

• The sural nerve is a sensory nerve supplying the posterolateral distal calf and lateral foot; it runs along the small saphenous vein (SSV), lies lateral to the Achilles tendon, and because of its proximity to the tendon may be affected by swelling from an Achilles tendon rupture and may be injured during surgical repair

Initial treatment

• Initially, pain can be relieved with ice, and analgesics such as paracetamol or non-steroidal anti-inflammatory drugs
• Immediately stopping activity is advised, using a support brace for immobilization (in about 20 to 30 degrees of plantar flexion) and avoiding aggravating the injured area; crutches can be used
• Steroid injection into the tendon should be avoided, because of the risk of causing Achilles tendon rupture

Additional treatment

• After surgery, management centers on rehabilitation and physical therapy, including stretching and strengthening exercises to promote flexibility and stimulate repair of the tendon tissue
• Eccentric strengthening exercises such as slow single-leg squats were associated with substantial pain reduction and functional improvement in studies
• Arch supports or orthotics may help patients with a collapsed arch or excessive pronation
• Night splints may provide relief in patients with chronic symptoms

Advanced treatment

• For patients with a partial tear who have not improved after 6 months of non-surgical treatment, surgery may be an option; for patients with a complete rupture, surgery is considered a priority
• Extracorporeal shock wave therapy (ESWT): in theory, it may induce neovascularization and an inflammatory process, thereby promoting tissue healing
• Advanced approaches include percutaneous tenotomy, platelet-rich plasma (PRP) injection, and ultrasound-guided tenotomy
• Over the past decade, results with regenerative medicine have been mixed. Some studies found that patients with PRP-augmented Achilles tendon rupture performed better on isokinetic muscle testing, with higher functional scores and improved ankle range of motion, while some articles concluded that patients receiving PRP treatment had no significant difference in outcomes compared with controls
• The potential benefits and risks of surgical intervention for Achilles tendon rupture remain debated; studies indicate that both surgical and non-surgical approaches can yield good functional outcomes and patient satisfaction. Compared with surgical intervention, conservative treatment has a higher re-rupture rate. However, with recent advances in rehabilitation programs, the difference in re-rupture rate between them has been greatly reduced (risk difference 1.6%)

Follow-up

• Patients treated non-surgically need 3 to 6 months to return to full activity
• After surgery, most patients can resume daily activities within 3 to 4 months and regain full athletic capacity within 6 to 18 months
• After surgery, follow-up every 4 to 6 weeks is advised to monitor recovery progress and adjust the rehabilitation program; post-operatively, attention is needed for wound care and brace adjustment, and a cast or brace shoe may be considered, with the plantar flexion angle fine-tuned every 2 to 4 weeks, initially kept around 30 degrees and then gradually reduced
• The re-rupture rate with non-surgical treatment is close to 40%, whereas it is only 0.5% in patients treated surgically
• The recurrence rate after surgery is lower, at about 5% to 20%, compared with 50% to 75% for non-surgical treatment

Phase 1: Immediate post-operative period (weeks 0 to 3)

Rehabilitation goals

• Protect the surgical repair site
• Maintain hip, knee, and core strength
• Control swelling

Weight-bearing and gait

• Non-weight-bearing (NWB), with a cast or heel support

Interventions

• Range of motion / mobility (performed inside the boot):
  • Supine passive hamstring stretch
• Strengthening (performed inside the boot):
  • Quadriceps sets
  • Straight-leg raises
  • Abdominal core stability training
  • Hip abduction exercises
  • Side-lying hip external rotation (clamshell)
  • Prone hip extension
  • Prone hamstring curls

Advancement criteria

• Pain under 5/10

Phase 2: Intermediate post-operative period (weeks 4 to 6)

Rehabilitation goals

• Continue protecting the repair site and avoid over-lengthening the Achilles tendon
• Reduce pain and swelling
• Improve scar mobility (after the wound has healed)
• Restore ankle plantar flexion, inversion, and eversion, and bring dorsiflexion to neutral

Weight-bearing and gait

• Week 4: begin progressive partial weight-bearing (using three 1-inch heel lifts)
• Week 5: remove 1 heel lift (2 remaining)
• Week 6: remove the 2nd heel lift (1 remaining)

Interventions

• Range of motion / mobility:
  • Active heel raises (limiting dorsiflexion to neutral)
  • Active ankle inversion and eversion
• Strength training:
  • Abdominal core training
  • Seated arch exercises
• Proprioception:
  • Joint position retraining

Advancement criteria

• Pain under 3/10
• Minimal swelling
• Dorsiflexion to neutral
• Normal gait in the Achilles boot (1 heel lift remaining)

Phase 3: Late post-operative period (weeks 7 to 8)

Rehabilitation goals

• Continue protecting the repair site and avoid over-lengthening the Achilles tendon
• Normal gait without heel lifts
• Restore full range of motion
• Build strength and promote normal movement patterns

Weight-bearing and gait

• Week 7: remove the last heel lift, normal gait
• Week 8: full weight-bearing (FWB), walking in the Achilles boot without crutches

Interventions

• Range of motion / mobility:
  • Strengthen dorsiflexion, progressing gradually
• Strength training:
  • Double-leg heel raises (progressing by weight-bearing proportion)
• Balance / proprioception:
  • Single-leg balance training (including perturbation training)

Advancement criteria

• No swelling or pain
• Normal gait in a boot without a heel wedge

Later phases (week 9 through 6-plus months post-op)

Key points by stage:

• Weeks 9 to 12: transition to athletic shoes (heel lifts gradually removed); add single-leg standing and strength training
• 3 to 6 months post-op: begin progressive power training (for example, single-leg hops)
• 6-plus months post-op: perform sport-specific training to restore full athletic capacity

Final graduation criteria

• Physician approval and completion of all milestones:
  • No pain or swelling after exercise
  • Single-limb functional tests reaching 90% or more of the uninvolved side
  • Completion of a running and power training program

References

1. Rehabilitation Protocol for Achilles Rupture Repair (Massachusetts General Brigham Sports Medicine)
2. Australas J Ultrasound Med. 2024 Apr 17;27(2):106-119.
3. J. Clin. Med. 2022, 11(16), 4722;
4. Int. J. Mol. Sci. 2021, 22(2), 824;

Further reading

• Foot and ankle injury overview
• PRP prolotherapy
• Rehabilitation exercise prescription
• Pain management