Injury Type and Classification in Sport

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Introduction

Being physically active or taking part in sports have many health benefits, but there is also the risk of injury. Sports injuries can occur anytime during training sessions or during when taking part in competition and various musculoskeletal connective tissue can be affected by injury. In sports epidemiology injury surveillance is important as it is key to understanding injuries and contributes to the development of injury prevention programmes.

Definitions

The International Olympic Committee Injury and Illness Epidemiology Consensus group defines injury as:

“Injury is tissue damage or other derangement of normal physical function due to participation in sports, resulting from rapid or repetitive transfer of kinetic energy.”

Classification of an injury refers to "the process of describing or categorising an injury (i.e. by its location, mechanism or underlying pathology)"

The grade of an injury refers to the severity of the injury.

Relationship of Injury to Sports Activity

Injuries may result:

• Directly from participation in sport (can be during competition or training)
  • Examples of this may include: collision between players or overuse from repetitive training

• Indirectly from participation in activities related to competition or training.
  • Example: athlete slipping and sustaining an injury when in the Olympic village

• Activities not related to participation in sports.
  • Example: athlete is involved in a car crash

Mode of Onset

Traditionally injuries are classified as injuries with a sudden onset (acute injury) or injuries with a gradual onset (overuse), but one also needs to consider an acute injury due to overuse.

• Acute episode = sudden injury because of an exchange of large quantities of kinetic energy (collision between athletes)
  • Mechanism is acute, and the presentation is sudden onset

• Overuse episode = gradual accumulation of low energy transfer over time (development of tendinopathy induced by repetitive movement or stress fracture)
  • Mechanism is repetitive, and the presentation is a gradual onset

• Acute episode due to overuse = combination of both mechanisms ( for example an athlete with a repetitive training regime resulting in tendinopathy or tendon weakness, but sustains an acute tendon tear during a jump)
  • Mechanism is repetitive, and the presentation is a sudden onset

Often a thorough subjective assessment and history taking will provide insight into the mode of onset. Radiological investigations may also be helpful in determining if an injury was an acute episode or whether it was an acute episode due to overuse.

Table 1. Examples: Assessment of Mode of Onset

Mechanism	Presentation	Example
Acute	Sudden onset	Sprinter pulls up suddenly in a race, stops and hobbles a few steps, in pain with a hamstring injury. Footballer falls on an outstretched hand, putting all the weight through the palm of the hand and hyperextending the wrist resulting in a scaphoid fracture
Repetitive	Gradual onset	Swimmer experiences a gradual increase in shoulder pain during the season, MRI indicates rotator cuff tendinopathy Dancer experiences progressive pain with and after activity and tenderness over the second metatarsal. Imaging indicates stress fracture of the second metatarsal
Repetitive	Sudden onset	Gymnast experiences a tibial fracture on landing from a vault; CT imaging reveals pre-existing morphological changes consistent with bone stress injury

Mechanism of Injury

This can be as a result of direct contact or non-contact mechanisms.

Table 2. Examples: Classification as a Mechanism for Injuries

Injury	Type of Contact	Example
Non-contact	No evidence of disruption of a player's movement patterns	Basketball player landing and twisting ankle with no contact with other players
Contact Indirect	Through another athlete	ACL tear in a football player landing off-balance after being pushed on his shoulder by an opponent while in the air
Contact Indirect	Through an object	Downhill skier suffers concussion from a crash after hitting the gate with his knee
Contact Direct	With another athlete	Rugby player sustains an ACL tear as a result of a direct tackle to the knee
Contact Direct	With an object	Volleyball player being hit in the face by a spiked ball, resulting in a concussion

Body Region Categories

Injuries can be further classified into the specific body region and more specifically the area involved.

Table 3. Categories of Body Regions and Areas for Injuries

Region	Body Area	Region	Body Area
Head and neck	Head Neck
Upper limb	Shoulder Upper arm Elbow Forearm Wrist Hand	Lower Limb	Hip/groin Thigh Knee Lower leg Ankle Foot
Trunk	Chest Thoracic spine Lumbosacral Abdomen	Unspecified	Region unspecified
Lower limb	Hip/groin Thigh Knee Lower leg Ankle Foot	Multiple regions	Single injury crossing ≥ 2 areas

Table of tissue

Muscle classification

Traditional Classification Systems

Muscle injuries are a common injury in sports. Historically a three-tier grading system based on clinical signs had been used to guide the prognosis of a muscle strain. Grading systems are useful in that it provides an indication of the severity or extent of the injury. With imaging advancements such as MRI and Ultrasonography, there is now the benefit of combining clinical and radiological findings and this has led to “new” muscle injury grading and classification systems over the last couple of years. (Brukner and Khan)

The table below is from the Munich Consensus statement on Terminology and classification of muscle injuries in sport and provide an overview of previous muscle injury classification systems

Table to be added and created

Modern muscle injury classification systems

Munich Consensus System

International clinical and basic science experts developed a comprehensive muscle injury classification and grading system.

Key points from Munich Consensus System:

Classification differentiates between direct (contusion and laceration) and indirect muscle injury

Indirect muscle injuries further classified as functional or structural injuries

Further subclassified into type of injury and subclassified into either a diagnostic group (e.g. fatigue induced muscle disorder ; delayed onset muscle soreness (DOMS); or muscle or spine related neuromuscular disorder) or severity grade (minor partial, moderate, subtotal, complete or avulsion).

Muscle injury is approached in a comprehensive way and includes descriptors such as acute, overuse, direct and indirect injury.

Read the full statement here: Terminology and classification of muscle injuries

in sport: The Munich consensus statement

Youtube video: https://www.youtube.com/watch?v=PhCxzDEE6Vc

British athletics system

Pollock et al designed a classification for non-contact muscle injuries, specifically relevant to the hamstring muscle (check this)

The system grades injury from 0 – 4, based on clinical and MRI features

The injury is then sub-classified further to reflect the principle anatomic structures involved: a = myofascial; b = within muscle usually at the musculotendinous junction; c = intra-tendinous tears

Grade 0 injuries – MRI negative and described as a “focal neuromuscular injury” or a muscle injury consistent with DOMS

If there is suspicion of a neural component involved  - N can be applied as additional differentiator

Grades 1 -3 refer to small, moderate or extensive tears respectively to the muscle tissue (determined by the extent of oedema and tissue disruption, as well as by tissue involved)

Grade 4 refer to complete tears of either muscle or tendon

Chan System

Chan et al proposed a 3-layered anatomical classification system, this is mainly an imaging based classification system

The injury’s anatomical location is proximal musculotendinous junction, muscle or distal musculotendinous junction.

The injury is then sub-classified as proximal, middle or distal

Thereafter the injury is defined by the principle tissue involved (e.g. intramuscular, myofascial, perifascial, myotendinous or a combination)

Barcelona System

Proposed a muscle injury classification and grading system based on 4 tiers/layers

From clinical history – mechanism of injury (direct or indirect)

Indirect injuries are further identified as sprinting or stretch related

Second and third identifiers are MRI variables – anatomical location and grade of injury

Fourth identifier relates to re-injury status

Read this study here Muscle Injuries in Sports: A New Evidence-Informed and Expert

Consensus-Based Classification with Clinical Application

Cohen system

Developed a hamstring injury classification system

Specifically for professional American football players

Novel scoring system based on age and a range of MRI variables

Read more about this here: Cohen S.B., Towers J.D., Zoga A., Irrgang J.J., Makda J., Deluca P.F. Hamstring injuries in professional football players: magnetic resonance imaging correlation with return to play. Sports Health. 2011;3:423–430

Recent reviews investigating muscle injury classification system

Time for a paradigm shift in the classification of muscle injuries https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6189241/ - good discussion points

Classification and grading of muscle injuries: a narrative review

An update on the grading of muscle injuries: a narrative review from clinical to comprehensive systems

Workshops on Muscle Injuries by Bruce Hamilton - New Zealand.

https://www.youtube.com/watch?v=ja3hE3v2RZs

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