Hamstring injuries remain one of the most frequent and frustrating injuries in sport. They account for a substantial proportion of time-loss injuries in elite athletics and professional football, are associated with high recurrence rates, and often pose significant challenges when determining an athlete's readiness to return to sport.

One of the biggest obstacles to managing these injuries has been the lack of a universally accepted classification system capable of accurately describing injury severity while also providing meaningful prognostic information. The British Athletics Muscle Injury Classification (BAMIC) was developed to address this challenge by combining MRI findings with anatomical location, allowing clinicians to better estimate recovery timelines and guide rehabilitation.

This blog post reviews the evolution of muscle injury classification, explains the BAMIC system, and discusses its practical application in clinical practice.

If you want to learn more about this topic, you can watch Marco Tabone's lecture here:

Click here

Why do hamstring injuries deserve special attention?

Hamstring muscle injuries are the most commonly injured muscle group in many running-based sports.

In professional football alone:

• • Hamstring injuries account for approximately 30% of all injuries.
• • Around 16% are recurrent injuries.
• • Recurrences typically result in longer absences than the original injury.
• • Injury incidence continues to increase despite advances in sports medicine.

Beyond the individual athlete, the impact on teams is considerable. An elite football squad can expect multiple hamstring injuries each season, leading to numerous missed training sessions and competitive matches.

An additional challenge is that approximately 40% of hamstring injuries involve the intramuscular tendon, a finding consistently associated with longer rehabilitation and an increased risk of recurrence.

Why traditional grading systems were not enough

Historically, muscle injuries were graded simply as Grade I, II or III based primarily on the presumed amount of tissue damaged.

These early systems provided a common language but had important limitations:

• • they lacked anatomical detail;
• • they offered limited prognostic accuracy;
• • they did not distinguish between injuries affecting different tissue structures;
• • they often used the terms classification and grading interchangeably.

With the widespread use of MRI, clinicians gained the ability to evaluate not only the size of an injury but also its exact anatomical location and the structures involved. This shift highlighted an important concept:

Not all muscle injuries with similar size behave similarly clinically.

The tissue injured often matters as much as the amount of tissue injured.

What makes BAMIC different?

Introduced by Pollock and colleagues in 2014, BAMIC combines injury severity with the anatomical structure involved.

Instead of relying solely on the size of the lesion, the system evaluates:

• • extent of muscle oedema;
• • muscle fibre disruption;
• • cross-sectional involvement;
• • longitudinal injury length;
• • tendon involvement;
• • tendon continuity and tension.
• • This provides a more clinically meaningful description of the injury.

The classification consists of Grades 0 to 4, with Grades 1–3 further subdivided according to the principal tissue involved.

A: Myofascial injuries

These injuries primarily involve the fascia surrounding the muscle.

Typical characteristics include:

• • relatively preserved strength;
• • pain during contraction;
• • diffuse tenderness;
• • limited architectural muscle disruption.

Because the contractile tissue remains largely intact, athletes often recover relatively quickly.

B: Myotendinous junction injuries

These injuries occur at the muscle-tendon junction, one of the most common sites of hamstring injury.

Clinically they usually present with:

• • pain during contraction;
• • reduced strength;
• • reduced flexibility;
• • greater functional impairment than myofascial injuries.

Recovery generally requires a more gradual progression than Class A injuries because the contractile apparatus has been disrupted.

C: Intratendinous injuries

Class C injuries involve the intramuscular tendon, making them particularly important from a rehabilitation perspective.

Although symptoms may improve relatively quickly, tendon healing occurs much more slowly than muscle healing.

Compared with muscle tissue, tendon repair depends on prolonged collagen synthesis, matrix remodelling, and restoration of tensile strength. Consequently, these injuries consistently demonstrate:

• • longer return-to-training times;
• • slower rehabilitation progression;
• • higher recurrence rates.

This distinction is one of BAMIC's greatest strengths and represents an important advance over earlier grading systems.

MRI findings should inform—not dictate—clinical decisions

MRI plays a central role in BAMIC by helping identify the anatomical structures involved.

However, clinicians should remember that imaging findings do not necessarily reflect functional recovery.

Research has demonstrated that many athletes who have safely returned to sport still show persistent oedema and fibrosis on MRI. In other words, functional recovery often precedes complete radiological healing.

This highlights an important clinical principle:

MRI should complement—not replace—a comprehensive clinical assessment that includes symptoms, strength, function, movement quality, and sport-specific performance.

Rehabilitation should reflect tissue biology

One of the most valuable aspects of BAMIC is its ability to guide rehabilitation according to the tissue that has been injured.

→ Myofascial injuries

Fascial tissue heals relatively quickly, allowing for earlier progression toward high-speed running and sport-specific activities.

→ Myotendinous junction injuries

These injuries require gradual restoration of force production, beginning with controlled loading before progressing to eccentric strengthening and higher running speeds.

→ Intratendinous injuries

These demand the most conservative progression.

Early rehabilitation focuses on maintaining muscle function while protecting the healing tendon. Stretching is delayed, eccentric loading is introduced more cautiously, and high-speed running is progressed over a longer period to respect tendon remodelling.

Rather than applying a one-size-fits-all protocol, BAMIC encourages clinicians to match rehabilitation to the biological behaviour of the injured tissue.

Conclusion

Effective management of hamstring injuries extends beyond determining the size of a muscle tear. Understanding which tissue has been injured is fundamental to prognosis, rehabilitation planning, and return-to-sport decision-making.

The British Athletics Muscle Injury Classification integrates imaging findings with clinically meaningful anatomical information, allowing clinicians to better appreciate the biological behaviour of different injury types. In particular, recognising injuries involving the intramuscular tendon can help explain prolonged recovery and justify more conservative rehabilitation strategies.

When combined with a thorough history, physical examination, functional testing, and sound clinical reasoning, BAMIC provides an evidence-informed framework that can improve communication, rehabilitation planning, and ultimately reduce the risk of reinjury.

If you want to learn more about this topic, you can watch Marco Tabone's lecture here:

Click here

Reference

Lecture: The British Athletics Muscle Injury Classification (BAMIC) in Hamstring Muscle Injuries by Dr Marco Tabone.