Muscle injuries are one of the most frequent causes of injury in sport. According to some studies, an elite-level soccer team can expect to suffer 15 instances of muscle injury every season, which is equal to more than 200 lost days of training for the entire team. Despite the significance of muscle injuries, there is still no objective and globally accepted classification that would support improved understanding and prognosis.

Recently, part of the FC Barcelona medical team, together with the Duke Sports Science Institute in the United States and the Aspetar Hospital in Qatar, have published an article in the journal Sports Medicine that establishes a new four point classification system. This model, which is already being used at the club, will facilitate communication between professionals and will support the treatment and rehabilitation process.

From Clinical Evaluation to a New Classification

“For a long time, muscle injuries were classified based on a clinical evaluation (that is, through what the athlete reported feeling and a physical examination), says Xavier Valle, FC Barcelona physician and the first author listed for the article. “Later, classifications based on imaging tests started to appear – such as ultrasound and magnetic resonance – which are more objective. However, protocols for taking action are not the same across all clubs, which makes conducting research more difficult. This is perhaps the reason why we still don’t have a widely-accepted classification system”, he continues.

In the last few years some different models have emerged, such as the Munich consensus statement or the British system. Both models use ambiguous terms, which makes it difficult to assess their true value or universality.

To establish the new classification, a protocol was established by which the available scientific evidence was thoroughly reviewed (especially for the hamstring and rectus femoris muscles) and several meetings were held whereby doctors from the three centers shared information and worked on reaching a consensus and agreement.

Finally, a four-point classification system was established, based on four letters: MLG-R, which refers to (M)echanism of the injury, (L)ocation of the injury, (G)rading of severity and number of muscle (R)e-injuries.

Broadly speaking, the criteria can be defined as follows:

• Mechanism: the injury can be direct (due to a contusion) or indirect (through overstretching or “sprint”). In general, direct injuries tend to have a better prognosis.
• Location of the injury: these can be located in the proximal, medial or distal third of the muscle and in relation to the proximal or distal myotendinous junction. The closer the injury to the tendon, the worse the prognosis will be.
• Grade of severity: on a scale of 0 to 3 depending on the quantity of edema and/or disorganization of the muscle fibers observed via magnetic resonance.
• Re-injury: prognosis is better in the first instance of an injury. Prognosis worsens depending on the number of previous injuries in the same zone.

“In general, the goal of the four points is to quantify the quantity of affected connective tissue,” explains Valle. (Connective tissue is a kind of matrix in which muscle cells are arranged and is fundamental for transmitting strength and muscle function). Nevertheless, despite the fact that these criteria are already being used, their reliability must still be evaluated. “It’s the next step;” confirms the specialist. “We now have a sample of more than 100 cases which will allow us to test the model.”

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In any case, the model is flexible and it is important that it remains a “living” concept, open to new emerging knowledge. “We are going to keep working on testing the model and building more solid conclusions,” affirms Valle. Currently, classification is based almost exclusively on data from imaging tests, not clinical evaluations. “We are also evaluating whether criteria such as the percentage of loss of strength due to the injury or the time elapsed before walking without pain could be incorporated, but at the moment there is no clear evidence for these two indicators.”

Nowadays, imaging tests are not sufficient (not considered useful) in terms of the decision about when to return to competition, but Valle is clear that an objective and appropriate classification would improve the accuracy of prognosis, allow treatment to be adjusted and reduce the risk of re-injury.”

That would be no small achievement.

The Barça Innovation Hub team