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Glimpse - Do We Need A New Muscle‐Specific Classification?
Justas Muzikevicius
November 15, 2024
Sports Med U | Educating Minds, Elevating Potential
Muscle Madness and Making a Case for Muscle‐Specific Classification Systems: A Leap from Tissue Injury to Organ Injury and System Dysfunction
Muscle Madness and Making a Case for Muscle‐Specific Classification Systems: A Leap from Tissue Injury to Organ Injury and System Dysfunction
In today’s letter
A proposal of a different muscle classification system
2 key Takeaways =
Muscle injuries should be assessed within the context of their specific anatomical and functional roles to ensure targeted and effective rehabilitation.
Developing muscle-specific classification systems can help communication among doctors & physios and lead to better treatment outcomes for commonly injured muscles
3 resources to check out to further you knowledge about muscles
Meme of the week: Avoiding the knife 🔪
Bite-size study - A glimpse into our Infographic
Clinical Tips & Full Infographic 👇
Deeper look
Aim of the study
The aim of the study is to propose muscle-specific classification systems for commonly injured muscles to improve communication, diagnosis, and management in sports medicine
Are All Muscles Created Equal?
The traditional 3-grade system for classifying muscle injuries has been around for years, but it’s not perfect.
Grade I (stretch injury): Small tear, less than 5% of muscle fibres disrupted.
Grade II (partial tear): Bigger tear, 5-50% fibre disruption, and noticeable strength loss.
Grade III (complete rupture): Over 50% of fibres disrupted, often leading to a total loss of strength and function.
This grading system has been used in clinical exams, ultrasound, and MRI scans. However, the system really starts to fall short when dealing with elite athletes.
In fact, in the last 8 years, there have been at least four new classification systems introduced to improve how muscle injury grading is done.
These new systems aim to be more practical and to give better predictions about recovery time.
That said, there’s still no clear distinction between Grade I (small tear) and Grade II (moderate tear) injuries when it comes to recovery outcomes.
Grade III injuries (severe tears) and injuries to the musculotendinous junction (where muscles connects to tendon) tend to have worse recovery timeframes.
MRI is usually used to assess the size and severity of the injury, which helps guide the rehab process. One study found that damage to the intramuscular tendon might actually be the best indicator of how long it will take to return to sport.
The major limitation of all these systems is that they try to apply a single classification across every muscle in the body.
This doesn’t account for the differences between muscles – some muscles have single or multiple tendons, some are uni- or bipennate, and so on.
So, injuries in different muscles, like the adductor longus versus the semitendinosus, might need muscle-specific classification systems to better reflect their unique anatomy and injury patterns
Biological, Structural and Systemic Approach to Muscles
A tissue is basically a group of similar cells that are organised to perform a specific function.
In the human body, there are four main types of tissues:
Epithelial
Connective
Muscle
Nervous tissue.
Each type of tissue is specialised due to differences in the cells and surrounding “structure” (called the extracellular matrix).
When the tissues come together in an organised structures to perform a function, they form organs.
Even though two organs might be made up of similar tissue types, they can still be quite different because of the specific subtypes.
For example, both the liver and pancreas have epithelial, connective, and nervous tissues, but differences in the types of epithelial cells make them function very differently.
Muscles are a great example too: the soleus and rectus femoris are both skeletal muscles, but their unique structures make them work in very different ways.
When we go one step higher in biological organisation, a group of organs that work together is called a system.
The functions of a system are more complex than just adding up what each organ does on its own.
Take the rectus femoris muscle: on its own, it helps extend the knee and flex the hip, but as part of the whole musculoskeletal system, it contributes to stabilisation of the knee during chage of direction and juming.
The soleus and rectus femoris have many similarities at the organ level but may have differences in their roles within the system (soleus is mostly involved in endurance while the rectus femoris is more explosive)
New Perspectives on Muscle Injuries
When thinking about muscle injuries, it might be more accurate to consider them as injuries to an organ, rather than just a local tissue injury.
These "organ" injuries should also be evaluated in the context of their role within the larger system they’re part of.
A classification system would be more useful in practice if it reflected how muscles function as organs within a system, used a common language, and included subcategories for muscles that are frequently injured
A good comparison here is the Association of Osteosynthesis (AO) classification system for fractures.
The AO system standardises how fractures are described and how data on them is managed.
It also includes subcategories that differentiate between types of bones—like long bones versus short bones—and even further breaks them down by region, like the upper versus lower limbs.
These subclassifications are meant to increase the specificity of diagnosis and treatment, making the classification more clinically useful.
Muscle injury classification systems, on the other hand, have so far been designed to apply to all muscles equally, which doesn’t account for the wide variety in muscle structure and function.
No current classification system takes into account the differences between muscles at the tissue, organ, or system level.
This is why we might need more specific subclassifications within general muscle injury systems, especially for the muscles that are injured most often.
Muscle‐Specific Classifications for the Most Common Injuries
Using a single classification system to describe all muscle injuries has its limitations, especially when it comes to effective communication between doctors and physios.
That’s why it might be more useful to have muscle-specific classification systems or at least subclassifications, for the most commonly injured muscles.
This approach is similar to how fracture classifications are handled, where specific systems exist for certain bones that are frequently injured and functionally important.
Most indirect muscle injuries tend to involve a few key muscles,
Hamstrings
Rectus femoris
Triceps surae (particularly the soleus and medial gastrocnemius)
Adductor longus.
While other muscles, like the pectoralis major or pectineus, can also be injured, the key muscles would benefit from having their own subclassification within a broader system to account for their unique anatomy, function, and recovery expectations.
These muscle-specific classifications should also consider the regional system that the muscle is part of, making communication and treatment planning more effective.
The detailed subclassifications would allow for more precise diagnoses and tailored treatment plans, ultimately improving patient care
Top 3 resources to check out
To further your knowledge about muscles
Credit: IG @Physiofunnies
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