What’s the difference between muscles, tendons and ligaments?

Physiotherapist Dominic Richmond explains the difference between the three most common soft tissue types; muscles, tendons, and ligaments and the most common types of injuries associated with them

What's the difference between muscles, tendons and ligaments

Soft tissues refer to parts of your body that are not bones or vital organs and while there are many, the three main ones we will focus on (and you will be familiar with) are muscles  (or to be more precise skeletal muscles), tendons and ligaments.

what are muscles
Credit: Getty Images

What are muscles?

We are all familiar with muscles and we all have them, whether you can see them or not!  In the most simplistic way possible the role of the muscle is to produce contractions (shortening) to facilitate movement.

what is the structure of a muscle

The muscle is a soft tissue made up of connective tissue (surrounding case) and individual muscle fibres, which are striated in appearance.  Each muscle fibre  contains protein filaments, which are responsible for producing contractions. This is what allows us to move around and these fibres are activated by motor nerves.

What are the most common muscle injuries?

Muscle injuries are very common and a normal part of life for the fit and active. The most common injuries are muscle strains, lacerations and contusions.

As previously mentioned muscles have the ability to stretch, however if they stretch too far or the force going through them exceeds the force they can produce, the fibres can go past their comfort zone. This causes separation of the fibres and produces a muscle strain. Muscle strains come in different grades (see below).  Symptoms are an immediate onset of pain following a sudden stretch or an unusual movement.


There is damage to individual muscle fibres (less than 5% of fibres).

This is a mild strain, which requires 2 to 3 weeks reduced activity with a slow and steady increase.

 There is more muscle fibres involved, but the muscle is not completely ruptured.

 The rehab period required is usually between 3 and 6 weeks with a slow and steady increase in activity to follow.

This is a complete rupture of a muscle. In an athlete this will usually require surgery to repair the muscle.

The rehabilitation time is around  3-6 months.

Lacerations are identical, in that there is separation of fibres however it is usually due to a sharp or slicing trauma to the muscles…we will not attach picture of this one – they are not for the squeamish!

How do you treat muscle aches and injuries?

Muscles have a great blood supply and left alone they will fully heal in 6-12 weeks depending on the severity of the strain.  A complete rupture would need surgical intervention followed by physiotherapy strengthening.

Muscles heal by bridging the separation with scar tissue which a) does not have a contractile element and b) is not as stretchy as the muscle.  So it is massively important to introduce exercises and stretches to the muscle to optimise recovery and the way the scar tissue is formed – this is where a physiotherapist can help!

For an optimal and speedy recovery the exercise programme has to be very specific for each muscle. This is so the muscle is not overloaded and overstretched to the point where it is detrimental to the healing process.

What are tendons?

what is a tendon

Tendons are the soft tissue that connects our muscles to the bone allowing them to be a pully and subsequently produce movement. Tendons differ from muscles because they are mainly made up of collagen and elastin; this means they cannot contract themselves, but they are incredibly strong and stiff. They also have a much smaller blood supply, reducing their metabolism.

Their stiffness means tendons have a remarkable ability to store and release energy like a spring. So much that the Achilles tendon can be responsible for 55-60% of your force production when running!

What are the most common tendon injuries?

Although uncommon you can have acute strains to tendons similar to the strain of a muscle. This is unusual due to the muscle being more ‘stretchy’ and therefore more likely to take one for the team.   The grading of these injuries are identical to the muscles strain, please see above.

A more common injury of the tendon is “tendinopathy” or “tendonitis” which are both the same thing. This refers to an overload of the tendon over a significant time period. These are really common just below the kneecap, in the Achilles and on the sole of the foot (plantar fasciitis).  The overload occurs during movements requiring the tendon to act like a spring e.g. jumping, running, throwing and walking.

How do you treat tendon injuries?

This injury reflects the fitness of a tendon along a continuum, so there is no quick fix! The very nature of this injury is that the tissue cannot cope with the work you are giving it.

Therefore, load (activity) modification is a HUGE part of rehabbing the tendon. Interestingly, the other part of the rehab process involves loading the tendon. Through lots of research it has been demonstrated that eccentric exercises and a slow and heavy load increase has a positive impact on the health of a tendon.

Some physios may prescribe eccentric resistance work and others slow and heavy resistance; this really depends on the stage of the tendinopathy and type… not forgetting that this in conjunction with you reducing the workload elsewhere.

 What are ligaments?

what is a ligament

Last, but certainly not least is the ligament; the primary role of this soft tissue is stability and it does this by connecting bone to bone.  Like tendons, ligaments do not have a contractile component or a very good blood supply.  Additionally, they are made up of collagen and elastin but have much smaller elastin properties, which means they are not as springy. This makes sense with their function being to stop unwanted movement.

What are the most common ligament injuries?

Similar to muscles and tendons, ligaments are susceptible to being over stretched causing the fibres to separate; this type of injury is referred to as a sprain.  You may recognise the table below or find it looks very similar to the muscle strain injury and that’s because … it is!


Represents a microscopic injury without stretching of the ligament on a macroscopic.

Little swelling & tenderness with little impact on function.

Considerably more fibres and, therefore there could be increased laxity at the joint.

Moderate swelling, pain and impact on function, reduced properoception, range of motion and instability.

Complete rupture with excessive joint laxity. Can be painful, but occasionally painless.

Complete rupture, large swelling, very tender, loss of function and noted instability of the joint

How do you treat ligament problems and injuries?

Complete ruptures of ligaments require surgery to be reconstructed, but other grades require appropriate rest followed by rehab exercises.

Rehab exercises for ligaments should focus on strengthening the surrounding muscles. This is to make sure the joint is as supported as possible. Controlled resistance exercise does not pose a threat to ligaments, therefore you can progress weights quite quickly.

In addition to strengthening it is important that you focus on proprioception rehabilitation with ligaments.  Ligaments are rich with mechanoreceptors, which are cells that tell your body where joints are in space.  If your body starts to move in unconventional ways that pose a threat to the ligaments, then it is important to have finite mechanoreceptors to trigger reflexes of postural muscles. They can also relay the information to you much quicker, so you know to correct your movement.

Proprioception (mechanoreceptor) training is very easily done … in principle.  Combining various types of balance work with jumping, changing direction, throwing and catching.

If you are worried about any kind of soft tissue injury always seek medical advice and get it checked out by a doctor or physiotherapist.  

Dominic Richmond is a Chartered Physiotherapist with Physio Fixx


Images by Getty Images