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Date Posted:

February 2014

Study Title:

Terminology and classification of muscle injuries in sport: The Munich consensus statement


Mueller-Wohlfahrt H-M, Haensel L, Mithoefer K et al.

Author's Affiliations:

MW Center of Orthopedics and Sports Medicine, Munich and Football Club FC Baayern Munich, Germany; Harvard Vanguard Medical Associates, Harvard Medical School, US Soccer Federation, Boston, Massachusetts, USA.

Publication Information:

British Journal of Sports Medicine 2013; 47: 342-350.

Background Information:

Injuries in sports are commonplace and although specific sports hold greater predisposition to athletic injuries than others, muscle injuries constitute a high percentage of injuries sustained in both contact and noncontact sports. Unfortunately, standardization in both terminology and classification of such injuries is not concrete and therefore, creates a window of opportunity for less than optimal diagnosis and management.

Previous attempts have been made to standardize muscle injuries, from grading systems based on clinical signs (Grades I-IV), to grading systems based on diagnostic imaging (MRI- and ultrasound-based). Unfortunately, such systems have traditionally lacked specificity in injury etiology and presentation and as a result, have prevented the diagnostic guidance necessary for optimal clinical management and return-to-play recommendations.

The objective of this consensus statement was to propose clear classification and terminology for muscle injuries to facilitate consistent and effective communication among clinicians in all disciplines, as well as assist in the development of systematic treatment strategies.

Pertinent Results:

In part one of this study, questionnaires were administered to 30 experts (19 replied). What emerged from their responses was distinct variability in definitions of various terms such as muscle strain, muscle tear and hypertonus.. Additionally, no consistency was found in the definitions of structural and functional muscle injuries. Moreover, none of the respondents considered a “tear” to be a functional injury, and thus the need for improved standardization in the terminology and classification of muscle injuries was highlighted.

The following definitions form the foundation of the consensus statement based on the experts’ one day meeting (part two of the study – see details below):

Functional Muscle Disorder:
  • Acute indirect muscle disorder ‘without macroscopic’ evidence (in MRI or ultrasound) of muscle tear.
  • Often associated with circumscribed increase of muscle tone (muscle firmness) in varying dimensions and are predisposing to tears. Based on the etiology, several subcategories of functional muscle disorders exist.
Structural Muscle Injury:
  • Any acute indirect muscle injury ‘with macroscopic’ evidence (in MRI or ultrasound) of muscle tear.
The following general recommendations were provided by the authors/experts:
  • The discontinued use of the term “strain” due to its biomechanical nature and variable use in anatomical and functional muscle injuries.
  • The discontinued use of the terms “pulled-muscle”, “hardening” and “hypertonus” for scientific purposes, due to lack of consistency in definition and their use as lay-man’s terms.
Classification System:
The following is a condensed summary of the proposed muscle injury classification system from this consensus statement.

Indirect Muscle Disorder/Injury (Functional muscle disorder) – 2 Types:
  • Type 1: Overexertion-related muscle disorders subclassified as Type 1A (Fatigue-induced muscle disorder) and Type 1B (Delayed-onset muscle soreness):
    • Type 1A: Longitudinal increase in muscle tone, described as aching/tight, and negative with imaging.
    • Type 1B: Generalized discomfort secondary to novel eccentric/deceleration movements/activities, reported stiffness and limited range of motion, negative with imaging.
  • Type 2: Neuromuscular muscle disorders subclassified as Type 2A (Spine-related neuromuscular muscle disorder) and Type 2B (Muscle-related neuromuscular muscle disorder):
    • Type 2A: Longitudinal increase in muscle tone secondary to functional or structural lumbopelvic disorder, described as aching although no pain at rest, edema between muscle and fascia as well as guarding upon clinical assessment, negative with imaging.
    • Type 2B: Increased tone secondary to dysfunctional neuromuscular control, often reported as “cramping”, relieved by therapeutic stretching, negative with imaging.
Indirect Muscle Disorder/Injury (Structural muscle disorder) – 2 Types:
  • Type 3: Partial muscle tear subclassified as Type 3A (Minor partial muscle tear) and Type 3B (Moderate partial muscle tear):
    • Type 3A: Maximum diameter of tear less than muscle fascicle/bundle, reported as sharp/stabbing upon injury often with a “snap” sensation, well-defined localized pain often with palpable defect, primarily located at the muscle-tendon junction, fiber disruption on MRI with intramuscular hematoma.
    • Type 3B: Diameter of tear greater than one fascicle/bundle, similar symptoms as Type 3A, often accompanied by visible hematoma, primarily located at the muscle-tendon junction, significant fiber and fascial disruption/intramuscular hematoma on MRI with possible retraction.
  • Type 4: Tear involving the partial or total muscle diameter or tendinous injury affecting the bone-tendon junction. Subclassified as either subtotal or complete muscle tear and tendinous avulsion:
    • Subtotal, complete tear or avulsion – dull sensation and noticeable tearing/defect, patient/athlete may hear a ‘snap’, hematoma present and loss of function, possible palpable gap, positive imaging
Direct Muscle Injury (Contusion):
  • Direct trauma secondary to blunt, external force, hematoma present, pain upon movement and decreased range of motion, athlete may continue activity, possible hematoma upon imaging
Direct Muscle Injury (Laceration):
  • No further description required.

Clinical Application & Conclusions:

This consensus statement by Mueller-Wohlfahrt and colleagues presents more precise definitions of muscle injury terminology and classification. As such, the facilitation of improved diagnostics, therapy and scientific communication seems likely provided this information is appropriate disseminated. Underlying this higher resolution of terminology however, sits the utmost importance of thorough history taking, physical examination and understanding of patient/athlete goals. Clearly stated in this consensus statement was the critical emphasis on the clinical assessment over reliance on imaging alone.

It is important to note, however, that although this paper is published as a consensus statement in the British Journal of Sports Medicine (a world-renowned journal), the proposed standardizations in terminology and classification have yet to be put through rigorous scientific analysis. Additionally, although the authors did provide greater detailed recommendations, such recommended terminology classifications may fail to recognize both the benefits (ex. length of lesions) and limitations of MRI findings (resolution ability) as suggested by Orchard et al in their follow-up editorial (see additional references below). Therefore, caution must be taken to accept this consensus statement as externally valid regardless of the fact that may seem to lead to improvements in clinical assessment and management. Further collaborative discussion and research is warranted.

Study Methods:

This paper was a consensus statement based on a two part endeavor by Mueller-Wohlfahrt and colleagues. In part one, the primary authors sent a questionnaire to 30 of the world’s leading sports medicine experts (19 of whom responded). The questionnaire consisted of three categories:
  1. Subjective descriptions and definitions of various terms of muscle injuries and the indication of whether the term was classified as functional or structural;
  2. the association of synonym terms of muscle injuries; and
  3. listing of provided muscle injury terms in order of severity.
In part two, the authors then organized a consensus meeting whereby 15 international muscle injury and sports medicine experts convened to apply a “nominal group consensus model approach” to create a consensus statement on terminology and classification of muscle disorders and injuries. The results of this meeting were then summarized in this consensus statement.

Study Strengths / Weaknesses

This was a collaborative expert opinion consensus statement. As such, no formal study limitations are present, aside from the general level of evidence such a project represents. Based on the topic at hand, this method of arriving at a collective expert opinion is appropriate.

Additional References:

  1. Johannes LT, Hamilton B & Best TM. “Palpating muscles, massaging the evidence” An editorial relating to ‘Terminology and classification of muscle injuries in sport: The Munich consensus statement’. British Journal of Sports Medicine. 2012; [epub ahead of print].
  2. Orchard JW, Best TM, Mueller-Wohlfahrt H-W et al. The early management of muscle strains in the elite athlete: best practice in a world with a limited evidence basis. British Journal of Sports Medicine, 2008; 42:158-159.

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