Torn achilles

A torn Achilles tendon, also known as an Achilles tendon rupture, is a serious injury that involves partial or complete tearing of the tendon connecting the calf muscles to the heel bone. It is one of the most common tendon injuries in the lower limb and frequently occurs in athletes or individuals engaging in sudden, forceful movements. Proper understanding of its anatomy, causes, and management is essential for timely diagnosis and optimal recovery.

Introduction

The Achilles tendon is the strongest and thickest tendon in the human body, allowing efficient transfer of muscular force from the calf to the foot for walking, running, and jumping. A tear or rupture of this tendon results in significant functional impairment, including weakness in plantarflexion and difficulty with weight-bearing activities. The injury is typically acute and occurs following a sudden increase in stress or force on the tendon, such as during sprinting, jumping, or abrupt directional changes.

Although common in middle-aged recreational athletes, Achilles tendon tears can affect anyone, particularly those with underlying tendon degeneration or systemic risk factors. Timely diagnosis and management are vital to restore tendon integrity, prevent long-term disability, and reduce the risk of re-rupture.

This article provides a comprehensive overview of the anatomy, causes, clinical presentation, and treatment of torn Achilles tendon, highlighting the importance of rehabilitation and preventive care in achieving full functional recovery.

Anatomy of the Achilles Tendon

Structure and Location

The Achilles tendon, also called the calcaneal tendon, connects the gastrocnemius and soleus muscles of the calf to the posterior surface of the calcaneus (heel bone). It begins near the mid-calf region where the muscle fibers of these two muscles converge into a common fibrous cord. Measuring approximately 15 cm in length, it tapers as it descends and inserts into the posterior aspect of the calcaneus.

• Origin: The tendon arises from the combined aponeuroses of the gastrocnemius and soleus muscles.
• Insertion: It attaches to the posterior surface of the calcaneus.
• Structure: Composed of dense, parallel collagen fibers primarily of type I collagen, providing high tensile strength.

A thin connective tissue sheath surrounds the tendon, facilitating smooth movement between the tendon and surrounding tissues. It is separated from the underlying bone by a bursa that reduces friction during movement. The Achilles tendon lacks a true synovial sheath and is instead enclosed by a paratenon, which aids in tendon gliding and vascular supply.

Blood Supply and Innervation

The tendon receives its blood supply mainly from branches of the posterior tibial artery and the peroneal artery. The central portion of the tendon, located approximately 2 to 6 cm above the calcaneal insertion, has relatively poor vascularity, making it prone to degeneration and rupture. Venous drainage corresponds to the arterial supply.

Innervation is provided by sensory branches of the sural nerve and, to a lesser extent, the tibial nerve. These nerves also transmit proprioceptive feedback, which is crucial for maintaining balance and coordination during movement.

Biomechanical Function

The Achilles tendon is responsible for transmitting the powerful contractile forces of the calf muscles to the foot, enabling plantarflexion of the ankle. This movement is fundamental for walking, running, jumping, and standing on the toes. The tendon can withstand forces up to 10 times a person’s body weight during high-impact activities.

• Role in movement: Facilitates propulsion during gait by storing and releasing elastic energy.
• Function during running: Acts as a spring that absorbs shock and aids efficient energy transfer.
• Role in stability: Provides dynamic support to the ankle and foot during movement.

Despite its strength, the Achilles tendon is vulnerable to injury due to repetitive stress, sudden overloading, and diminished blood supply in its mid-portion. Understanding its anatomical and biomechanical characteristics helps explain why tears frequently occur in this region.

Definition and Overview of Achilles Tendon Tear

A torn Achilles tendon, or Achilles tendon rupture, refers to a disruption of the tendon fibers that connect the calf muscles (gastrocnemius and soleus) to the calcaneus. The extent of the injury can range from a minor partial tear involving only some fibers to a complete rupture where the tendon is fully severed. This condition leads to immediate loss of tendon continuity and significant impairment in ankle movement, particularly in plantarflexion.

The most common site of rupture is the tendon’s midsubstance, approximately 2 to 6 cm above its insertion into the calcaneus, where the blood supply is weakest. This zone of hypovascularity contributes to degenerative changes and reduced healing capacity, making it especially susceptible to injury. Less commonly, tears may occur near the musculotendinous junction or at the calcaneal insertion.

The mechanism of injury typically involves sudden, forceful plantarflexion of the ankle or dorsiflexion of the foot while the calf muscles are contracting. It often occurs during activities that require abrupt acceleration, deceleration, or jumping. Affected individuals frequently describe a sharp pain or a snapping sound at the moment of rupture, followed by weakness and difficulty bearing weight on the affected leg.

• Partial tear: Only a portion of the tendon fibers is disrupted; some continuity remains, allowing limited movement.
• Complete tear: The tendon is fully ruptured, leading to loss of plantarflexion strength and a palpable gap above the heel.

Recognizing the nature and extent of the tear is essential for guiding appropriate treatment, as partial ruptures may respond to conservative care while complete ruptures often require surgical intervention.

Etiology and Risk Factors

Intrinsic Factors

Several intrinsic or internal factors contribute to the likelihood of Achilles tendon rupture. These include biological and physiological characteristics that affect tendon strength, elasticity, and repair capacity. With age, the tendon undergoes degenerative changes, such as decreased collagen organization and reduced vascularity, which weaken its structural integrity.

• Age-related degeneration: The risk of rupture increases in individuals aged 30 to 50 years due to cumulative microtrauma and decreased tendon resilience.
• Chronic tendinopathy: Long-standing inflammation or tendinosis weakens tendon fibers and predisposes them to tearing under stress.
• Systemic diseases: Conditions such as diabetes mellitus, rheumatoid arthritis, and chronic renal failure can impair tendon metabolism and healing.
• Genetic and metabolic factors: Collagen synthesis abnormalities and lipid deposition within tendons can reduce tensile strength.

Extrinsic Factors

External factors often precipitate tendon rupture by placing sudden or excessive strain on an already compromised tendon. These include environmental, pharmacological, and biomechanical influences that increase stress or reduce tendon adaptability.

• Sudden increase in activity: Rapid escalation in exercise intensity or duration without adequate conditioning can overwhelm tendon capacity.
• Improper warm-up or stretching: Insufficient preparation before strenuous activity reduces tendon flexibility, increasing injury risk.
• Fluoroquinolone and corticosteroid use: Both oral and injected corticosteroids, as well as fluoroquinolone antibiotics, have been associated with tendon weakening and rupture.
• Mechanical overloading: High-impact activities such as basketball, tennis, or sprinting that involve explosive movements place excessive tension on the tendon.
• Inadequate footwear: Poor shock absorption and lack of heel support alter gait mechanics, predisposing the tendon to repetitive strain.

In many cases, intrinsic degeneration and extrinsic stressors act together to cause rupture. For example, an aging tendon with chronic microdamage may rupture suddenly during a powerful push-off movement. Identifying these risk factors helps guide both preventive strategies and individualized treatment approaches for those prone to Achilles tendon injury.

Pathophysiology

The pathophysiology of a torn Achilles tendon involves a combination of mechanical overload, degenerative changes, and impaired healing capacity. The tendon is subjected to repetitive tensile stress during activities such as running and jumping, which can cause microscopic injuries over time. When these microtears accumulate faster than the tendon can repair, structural weakening occurs, predisposing it to rupture under sudden strain.

Degenerative changes, often described as tendinosis, include disorganization of collagen fibers, decreased cellularity, and an increase in non-collagenous matrix material. The middle segment of the tendon, approximately 2 to 6 cm above the calcaneus, is particularly vulnerable due to its limited blood supply and lower oxygen tension. This zone, often termed the “watershed area,” is where most spontaneous ruptures occur.

• Mechanical stress: Repetitive loading leads to collagen fiber fatigue and microdamage.
• Vascular insufficiency: Limited circulation in the tendon reduces nutrient delivery and impairs repair processes.
• Cellular degeneration: Tenocytes lose their ability to maintain collagen integrity, leading to fiber fragmentation.
• Inflammatory response: Chronic low-grade inflammation promotes matrix degradation and weakens tendon architecture.

During an acute rupture, the tendon typically fails at its weakest point under extreme tension, often during sudden dorsiflexion of the ankle with the calf muscle contracted. The rupture results in separation of tendon ends and bleeding within the surrounding paratenon. Without timely repair, the tendon may heal with fibrosis or elongation, leading to reduced strength and persistent functional impairment.

Clinical Features

Symptoms

The presentation of a torn Achilles tendon is often sudden and dramatic. Most patients describe a sharp, stabbing pain in the back of the ankle or calf at the moment of injury, sometimes accompanied by a sensation of being “kicked” or struck from behind. This is frequently followed by swelling, difficulty walking, and loss of strength in the affected leg.

• Sudden pain in the posterior lower leg or ankle during activity
• Audible or palpable “pop” at the time of rupture
• Immediate weakness in plantarflexion (pushing off the foot)
• Difficulty standing on tiptoe or walking normally
• Swelling and bruising along the calf or heel area within hours

Signs

Physical examination reveals several characteristic signs that aid in diagnosing Achilles tendon rupture. The most notable is the palpable gap in the tendon, typically located a few centimeters above the heel. The affected ankle often shows loss of contour, with swelling and tenderness over the rupture site. Passive dorsiflexion may appear increased due to the lack of resistance from the severed tendon.

• Palpable defect: A discontinuity in the tendon felt on gentle palpation along its course.
• Positive Thompson test: Absence of plantarflexion when the calf is squeezed indicates complete rupture.
• Reduced plantarflexion strength: The patient struggles to push off the ground or stand on tiptoe.
• Localized swelling and ecchymosis: Indicate recent soft tissue injury and bleeding within the paratenon.

In partial tears, symptoms may be less dramatic, and some plantarflexion ability is retained. However, untreated or misdiagnosed cases can progress to complete rupture or result in chronic tendon elongation, causing long-term functional deficits.

Classification

Achilles tendon tears are classified based on the extent, location, and chronicity of the injury. Accurate classification is important because it guides treatment decisions and helps predict functional outcomes. The primary distinctions include partial versus complete rupture, acute versus chronic tears, and location-based categorization.

• Partial rupture: Involves incomplete tearing of the tendon fibers, with some continuity preserved. The patient may retain limited plantarflexion strength, and symptoms are often less severe.
• Complete rupture: Represents full-thickness disruption of the tendon, leading to total loss of continuity between the calf muscles and the heel bone. Functional movement is significantly impaired.
• Acute tear: Occurs suddenly, often following a traumatic event, and is diagnosed within the first few weeks of injury.
• Chronic tear: Refers to a neglected or missed rupture that has persisted for more than 4 to 6 weeks, typically with tendon retraction and fibrotic scarring.

Location-Based Classification

The Achilles tendon can rupture at various sites along its length, each with distinct characteristics and implications for treatment:

• Proximal rupture: Occurs near the musculotendinous junction, often related to eccentric overload during contraction.
• Midsubstance rupture: The most common type, located 2–6 cm above the calcaneal insertion where blood supply is poorest.
• Distal or insertional rupture: Occurs near the tendon’s attachment to the calcaneus, sometimes associated with avulsion injuries or calcific tendinopathy.

This classification helps clinicians determine the appropriate management approach. For instance, complete midsubstance ruptures are often treated surgically, whereas partial or proximal tears may respond well to conservative management if diagnosed early.

Diagnosis

Clinical Evaluation

Diagnosis of a torn Achilles tendon begins with a detailed history and physical examination. Patients typically describe a sudden onset of pain during activities involving rapid acceleration or jumping. The clinician should inquire about prior tendon pain, recent medication use, and level of physical activity.

• Inspection: Swelling, bruising, and deformity in the posterior ankle region are commonly observed.
• Palpation: A palpable gap may be felt along the tendon’s course, usually several centimeters above the calcaneus.
• Functional testing: Inability to stand on tiptoe or weak plantarflexion suggests significant tendon disruption.
• Thompson test: Performed with the patient lying prone and the knee flexed; squeezing the calf fails to produce foot plantarflexion if the tendon is ruptured.

These clinical signs are often sufficient to confirm the diagnosis, particularly in acute cases, although imaging studies may be used to assess the extent of injury and rule out partial tears or associated pathologies.

Imaging Studies

Imaging plays an essential role in confirming the diagnosis, evaluating tear severity, and planning appropriate treatment, especially in cases where clinical findings are equivocal.

• Ultrasound: A rapid, cost-effective, and reliable method for visualizing tendon discontinuity. It can differentiate between partial and complete tears and assess tendon gap size.
• MRI: Provides detailed visualization of soft tissue structures, useful in chronic or complex cases. MRI can identify partial tears, degree of retraction, and associated degenerative changes.
• X-ray: Though not diagnostic for tendon injuries, it can help exclude avulsion fractures or calcaneal involvement.

Ultrasound is typically preferred for initial evaluation due to its accessibility and real-time dynamic assessment, whereas MRI is reserved for preoperative planning or chronic ruptures where precise structural mapping is required.

Together, clinical assessment and imaging allow accurate classification and tailored treatment planning, ensuring optimal recovery and minimizing complications such as misdiagnosis or delayed intervention.

Differential Diagnosis

Because several conditions can mimic the symptoms of a torn Achilles tendon, careful evaluation is necessary to establish an accurate diagnosis. Differentiating between these conditions ensures appropriate management and prevents unnecessary interventions. Common differential diagnoses include inflammatory, degenerative, and muscular injuries in the posterior leg and ankle region.

• Achilles tendinitis or tendinopathy: Characterized by chronic pain, stiffness, and swelling of the tendon without a complete tear. Unlike rupture, plantarflexion strength is usually preserved, and there is no palpable gap.
• Gastrocnemius or soleus muscle strain: Involves overstretching or partial tearing of muscle fibers higher up in the calf. Pain is localized more proximally and often less severe than in a rupture.
• Retrocalcaneal bursitis: Inflammation of the bursa located between the Achilles tendon and calcaneus. Pain and swelling occur near the heel but without sudden onset or functional loss.
• Posterior ankle impingement syndrome: Caused by soft tissue compression during plantarflexion, commonly seen in athletes and dancers. Symptoms worsen with repetitive motion rather than acute trauma.
• Deep vein thrombosis (DVT): May present with calf pain and swelling, but lacks the mechanical deficit or palpable defect found in tendon rupture.

A combination of physical examination findings and imaging studies is used to differentiate these conditions. The presence of an audible pop, sudden weakness, and a positive Thompson test strongly support the diagnosis of Achilles tendon rupture.

Management and Treatment

Initial Management

Immediate care following an Achilles tendon rupture focuses on reducing pain, swelling, and further tendon damage. Early immobilization and proper first aid can improve outcomes and reduce the risk of complications.

• RICE protocol: Rest, Ice, Compression, and Elevation help control inflammation and prevent secondary injury.
• Immobilization: The affected leg should be immobilized in slight plantarflexion using a splint or brace to approximate the torn tendon ends.
• Pain management: Non-steroidal anti-inflammatory drugs (NSAIDs) may be used for pain relief, though prolonged use should be avoided to prevent delayed healing.
• Non-weight-bearing: Crutches or a walking boot are recommended to avoid stress on the injured tendon until definitive treatment begins.

Prompt referral to an orthopedic specialist is crucial for determining whether surgical or non-surgical treatment is most appropriate based on the patient’s age, activity level, and extent of tendon rupture.

Non-Surgical Management

Conservative treatment is suitable for patients with partial tears, low physical activity levels, or contraindications to surgery. It involves immobilization followed by structured rehabilitation to allow the tendon to heal naturally.

• Functional bracing: The ankle is immobilized in an equinus position (plantarflexion) for 6 to 8 weeks, gradually returning to a neutral position to promote tendon healing.
• Early mobilization: Controlled movement under supervision encourages proper collagen alignment and minimizes stiffness.
• Rehabilitation: A phased program focusing on stretching, strengthening, and proprioceptive training helps restore range of motion and strength.

Non-surgical management has shown comparable outcomes to surgical repair in select patients, particularly when functional rehabilitation begins early. However, there is a slightly higher risk of re-rupture compared to operative repair.

Surgical Management

Surgical repair is generally recommended for younger, active individuals or those seeking a faster return to sports and physical activity. The goal is to restore tendon continuity, tension, and function while minimizing re-rupture risk.

• Open repair: A traditional approach where the tendon ends are directly sutured under visualization. It provides strong mechanical stability but carries a small risk of wound complications.
• Percutaneous repair: A minimally invasive technique performed through small incisions, offering faster recovery and reduced infection risk while maintaining good functional results.
• Postoperative care: The ankle is immobilized for approximately 2 weeks, followed by gradual mobilization and physiotherapy. Weight-bearing is introduced progressively as healing advances.

Surgical repair typically allows for quicker return to high-demand activities and has a lower rate of re-rupture. However, it requires strict postoperative care to prevent complications such as infection, nerve irritation, or tendon elongation.

Rehabilitation and Recovery

Phases of Rehabilitation

Rehabilitation following an Achilles tendon tear is a crucial component of recovery, regardless of whether treatment was surgical or non-surgical. The goal is to restore tendon strength, flexibility, and function while preventing re-rupture or elongation. Rehabilitation typically proceeds through progressive stages that emphasize protection, mobility, and strengthening.

• Phase 1 – Immobilization and protection (Weeks 0–2): The ankle is immobilized in a plantarflexed position using a cast or boot to allow the tendon ends to approximate and begin healing. Weight-bearing is avoided or minimized.
• Phase 2 – Controlled mobilization (Weeks 2–6): Gradual introduction of limited range-of-motion exercises begins under supervision. Partial weight-bearing may be allowed using a heel lift or supportive brace.
• Phase 3 – Strengthening and functional restoration (Weeks 6–12): Gentle strengthening of the calf muscles is initiated using resistance bands or pool therapy. The focus is on regaining normal gait and balance.
• Phase 4 – Advanced training and return to activity (Weeks 12+): Plyometric exercises, sport-specific training, and proprioceptive drills are incorporated to rebuild endurance and agility. Return to competitive sports is typically allowed after 5–6 months, depending on recovery progress.

Rehabilitation protocols may vary based on the type of repair and the patient’s activity level. Close monitoring by a physiotherapist ensures gradual progression without overloading the healing tendon.

Return to Activity

Returning to physical activity after a torn Achilles tendon requires a cautious and structured approach to ensure complete healing and to minimize re-injury risk. The decision is guided by clinical evaluation, strength testing, and functional performance assessments.

• Criteria for return to sports: Full range of motion, near-normal calf strength compared to the opposite leg, absence of pain or swelling, and the ability to perform single-leg heel raises.
• Typical timeline: Light jogging may begin around 3 to 4 months post-injury, with full participation in high-impact or competitive activities around 6 to 9 months.
• Preventive strategies: Ongoing strengthening, stretching, and use of supportive footwear can reduce future tendon strain.

Individualized rehabilitation plans tailored to age, occupation, and athletic goals are essential. Overly aggressive or premature return to activity increases the risk of re-rupture or chronic weakness, whereas delayed rehabilitation may cause stiffness and loss of function.

Complications

While the prognosis for Achilles tendon rupture is generally favorable, several complications can arise during the healing or postoperative period. These complications may affect functional recovery and overall tendon strength, underscoring the need for careful management and follow-up.

• Re-rupture: One of the most significant risks, particularly in the first year after injury. The likelihood is slightly higher in conservatively managed cases but can also occur after surgical repair if rehabilitation is inadequate.
• Infection: A potential postoperative complication, especially with open surgical techniques. Proper wound care and aseptic measures reduce this risk.
• Tendon elongation: Overstretching of the healing tendon can lead to decreased push-off strength and impaired performance.
• Deep vein thrombosis (DVT): Prolonged immobilization and reduced mobility may increase the risk of venous thrombosis in the affected limb.
• Adhesion and scar formation: Excessive scar tissue can restrict tendon gliding, leading to stiffness and limited range of motion.
• Nerve injury: The sural nerve may be inadvertently injured during surgery, causing numbness or paresthesia along the lateral foot and ankle.

Early detection and management of these complications are crucial for achieving optimal outcomes. Adherence to rehabilitation protocols, proper surgical technique, and active patient participation play key roles in minimizing long-term deficits and restoring full functional capability.

Prognosis and Long-Term Outcomes

The prognosis for a torn Achilles tendon is generally favorable when timely and appropriate treatment is provided. Most individuals regain normal walking ability within three months and can return to sports or vigorous physical activity within six to nine months, depending on the severity of the rupture and adherence to rehabilitation protocols. Early intervention, proper alignment of the tendon ends, and progressive physiotherapy are the most important factors influencing successful recovery.

• Functional recovery: Patients treated with either surgical or non-surgical methods can achieve 80–100% of their pre-injury strength and mobility with comprehensive rehabilitation.
• Re-rupture rates: Surgical treatment generally carries a lower re-rupture rate (2–5%) compared to conservative management (5–12%), though early functional rehabilitation reduces this gap significantly.
• Return to sports: Most athletes return to competitive activities within 6–9 months, though some experience slight residual weakness or stiffness in the affected leg.
• Long-term strength and endurance: Minor deficits in calf strength and endurance may persist for up to a year post-injury, especially in high-performance athletes.

Long-term outcomes are highly dependent on the quality of rehabilitation and prevention of complications. Chronic ruptures or delayed treatment can lead to tendon elongation and reduced functional capacity. Nevertheless, with modern surgical techniques and evidence-based rehabilitation programs, most patients experience excellent restoration of mobility and strength.

Prevention

Preventing Achilles tendon rupture involves maintaining tendon flexibility, strength, and proper conditioning. Prevention strategies are particularly important for individuals who engage in high-impact sports, those with a history of tendinopathy, or those resuming physical activity after periods of inactivity. Gradual progression of training intensity and regular tendon care are key to reducing injury risk.

• Warm-up and stretching: A proper warm-up routine that includes calf stretching and dynamic movements enhances blood flow and tendon elasticity, preparing the tendon for activity.
• Strengthening exercises: Eccentric calf muscle strengthening improves tendon resilience and reduces microtears. Heel-raise exercises and resistance training are beneficial.
• Gradual increase in activity: Avoid sudden escalation in workout intensity or volume, particularly after long breaks from exercise.
• Footwear selection: Supportive shoes with good cushioning and heel stability help reduce stress on the Achilles tendon during running or jumping.
• Rest and recovery: Adequate rest between training sessions prevents overuse injuries and allows microtears in the tendon to heal properly.
• Addressing underlying conditions: Managing risk factors such as obesity, poor biomechanics, or systemic illnesses can reduce tendon stress and degeneration.

Consistent adherence to these preventive strategies helps maintain tendon health and minimizes the likelihood of future ruptures. For athletes, regular medical screening and individualized conditioning programs further enhance long-term tendon durability and performance.

Recent Advances and Research

Recent developments in the understanding and management of Achilles tendon ruptures have led to significant improvements in patient outcomes. Advances in surgical techniques, biological therapies, and rehabilitation protocols continue to enhance healing rates, reduce complications, and shorten recovery time. Current research focuses on optimizing both non-surgical and surgical approaches through the use of regenerative medicine and evidence-based rehabilitation strategies.

• Minimally invasive surgical techniques: Newer percutaneous and mini-open repair methods have been developed to reduce surgical trauma, minimize scarring, and decrease postoperative complications such as infection or nerve injury.
• Augmentation with biological materials: The use of synthetic scaffolds, allografts, and autologous tissues can strengthen tendon repairs and improve healing in chronic or complex ruptures.
• Platelet-rich plasma (PRP) therapy: PRP injections deliver concentrated growth factors to the injury site, stimulating collagen synthesis and tissue regeneration, though results vary across studies.
• Stem cell therapy: Experimental use of mesenchymal stem cells (MSCs) is showing promise in promoting tendon repair by enhancing angiogenesis and collagen organization.
• Enhanced rehabilitation protocols: Early functional rehabilitation emphasizing controlled motion and partial weight-bearing has been proven to accelerate healing while reducing stiffness and re-rupture risk.
• Advanced imaging techniques: High-resolution ultrasound and MRI are now used not only for diagnosis but also to monitor tendon healing and guide individualized rehabilitation programs.

These advances are shifting clinical practice toward less invasive, biologically enhanced, and functionally oriented management approaches. Continued research into tendon biology and regenerative medicine holds the potential to further improve outcomes for patients suffering from Achilles tendon injuries.

References

1. Leppilahti J, Orava S. Total Achilles tendon rupture: A review. Sports Med. 1998;25(2):79–100.
2. Maffulli N, Kader D. Tendinopathy of tendo Achillis. J Bone Joint Surg Br. 2002;84(1):1–8.
3. Willits K, Amendola A, Bryant D, et al. Operative versus nonoperative treatment of acute Achilles tendon ruptures: a multicenter randomized trial. J Bone Joint Surg Am. 2010;92(17):2767–2775.
4. Twaddle BC, Poon P. Early motion for Achilles tendon ruptures: is surgery important? A randomized, prospective study. Am J Sports Med. 2007;35(12):2033–2038.
5. Maffulli N, Via AG, Oliva F. Chronic Achilles tendon rupture and neglected tears: Current concepts review. Muscles Ligaments Tendons J. 2015;5(4):367–375.
6. Keating JF, Will EM. Operative versus non-operative treatment of acute rupture of tendo Achillis: a prospective randomised evaluation of functional outcome. J Bone Joint Surg Br. 2011;93(8):1071–1078.
7. Metz R, Verleisdonk EJ, van der Heijden GJ, et al. Acute Achilles tendon rupture: Minimally invasive surgery versus nonoperative treatment with immediate full weightbearing—a randomized controlled trial. Am J Sports Med. 2008;36(9):1688–1694.
8. Hsu AR, Jones CP, Cohen BE, Davis WH, Ellington JK, Anderson RB. Clinical outcomes and complications of percutaneous Achilles repair. Foot Ankle Int. 2015;36(12):1279–1286.
9. Kannus P, Józsa L. Histopathological changes preceding spontaneous rupture of a tendon: A controlled study of 891 patients. J Bone Joint Surg Am. 1991;73(10):1507–1525.
10. Yasui Y, Tonogai I, Rosenbaum AJ, et al. The use of biologics in Achilles tendon healing and repair: a review of the current literature. Foot Ankle Int. 2017;38(9):1025–1039.