What is a Muscle Strain or Tear?

Have you ever wondered if that muscle pain you feel is a strain or micro-tear, or a full-blown rupture…?

In this article, I’m going to clear up the confusion and talk about what actually happens when you have a muscular injury.

Anatomy of a Muscle?

Before we dive into the types of muscle tears, let’s talk about what makes up a muscle. In anatomy books, muscles look like a single structure with a name.

As athletes, you are already familiar with some of the names of these muscles, or at least the muscle groups (i.e., hamstrings, quads, glutes, etc). These pictures are actually a little misleading! 

Our muscles are not individual structures. In the picture above, you can see that each muscle is made up of hundreds of individual muscle fibres. These fibres are then grouped together and wrapped in connective tissue, ‘fascicles’ as shown in the picture above.  All of these groups are then joined together and wrapped in more connective tissue and fascia creating a single muscle.

That protective covering of fascia and connective tissue is then what creates the tendons that attach the muscle to bone (one tendon on each side).

In medical terminology, the point where muscle becomes tendon is called the musculotendinous junction.

structure of a muscle

So why are muscles made up of groups of muscle fibres versus one big muscle fibre that does it all?

Things are arranged this way so that we can vary our efforts.

For easy tasks, we may only require a few groups to contract. For harder, maximum efforts, we will need every group of fibres working to its full ability.

This is known as recruitment and it is achieved by the nerves that supply the muscle. Messages from our brain and reflexes allow us to contract our muscles and also allow us to relax them.

Why do muscles tear?

If a muscle is unable to adequately respond to / meet the demands of a task, it can become overloaded and tear under strain.

This can happen for a few reasons: The muscle contraction required to perform the movement may be more than the muscle can generate. There was not enough time to fully recruit the required muscle fibres. Restrictions in the muscle itself (mobility, strength, etc.,) prevented that full contraction.

Another reason is that muscles contract in two ways. The first is the normal shortening contraction (concentric). The second is a decelerating contraction where the muscle slowly lengthens to slow-down movements. In most muscular injuries, the second type of contraction, an eccentric contraction is more commonly the culprit.

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What is a muscle tear?

All muscle tears are technically muscle strains. Different words – same meaning. This occurs when muscle fibres are overloaded and fibres start to rupture under the force.

The percentage of muscle fibres involved and the severity of that tear are what determine the classification of the strain. Below you will find the three grades used by your doctor to diagnose the injury.

Here’s a great video that explains the different grades of muscle strains and micro-tears.

Grade I Muscle Strain:

Mild strain. Only a small number of fibres (< 5%) are stretched or torn. While the injury may be painful, strength and mobility are unaffected and recovery is quicker. Grade I is “micro-tear” territory. The fibres have been pushed to the point of starting to tear but not completely.

Grade II Muscle Strain:

Moderate strain. More fibres are involved and torn with grade two muscle strains. Grade II is a much larger injury and the symptoms reflect that. Symptoms include pain, swelling and bruising/discolouration. Strength and mobility are significantly diminished. The function of the muscle is also impacted.

Grade III Muscle Strain:

Complete rupture of a muscle. In a grade III tear, a muscle or its tendon are completely torn in two. This is a severe injury and includes considerable swelling, bruising, and pain. There is also a complete loss of muscle function with significant losses in strength and mobility. Due to the severity of this injury, you may also see visible defects in the muscle (gaps, dents, changes to the muscle shape itself) as the swelling subsides.

Where Do Muscle Tears Occur?

Typically muscle tears occur in one of three places:

  • Within the muscle belly itself (think: the meaty section of the muscle)
  • Where the tendon attaches to the bone
  • At the junction between the muscle and tendon (aka the musculotendinous junction). This is the most common area of the three.

Following the injury, there is an immediate period of inflammation and symptoms including pain, swelling, bruising/discolouration, and muscle cramps/spasms.

As the muscle heals, the damaged fibres will start to heal and scar tissue develops. Over time, the scar tissue will remodel and function will return, however, the muscle will never fully regenerate.

The site of injury will always contain scar tissue. This is why injured areas are prone to re-injury.

How long does it take to recover from a muscle tear?

Recovery times will vary based on the severity of the strain. For a Grade I muscle strain or micro-tear, full recovery is usually 2-6 weeks and athletes are able to resume activity when they are pain-free. Grade II muscle strains are more severe and take longer, averaging 2-3 months to fully heal the damage.

In the event of a complete rupture, medical care and often surgery are involved creating a much longer recovery time.

In our next post, we will talk about what you can do on your own to speed up your recovery following a muscle strain or micro-tear.

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Last updated on March 2nd, 2021.

1 Comment

  1. I have a spinal cord injury and have had a grade 2 muscle tear in my left thigh muscle from walking. Ever since then sometimes when I walk I will feel a tear and burn In that left thigh muscle. Sometimes it can be bad enough that my calf will start to swell. Are these grade 1 muscle tears?