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  • Writer's pictureUltra Sports

Sprain vs Strain?

Updated: Feb 10, 2019

Sprains vs Strains: Knowing the Difference

Strains and sprains are among the most common conditions seen at Ultra Sports Clinic. Various studies have shown that these injuries account for the majority of sports-related injuries. With this in mind, we wanted to help our patients understand what each of these conditions consists of. To do that, we will explain some basic anatomy, how each of these injuries can happen as well as how these injuries are diagnosed.


“Of the weight of a human in decent shape – all too few of us – muscle makes up 40 percent. Not blood, bone, brain, or liver contributes as much; only together do they add up to our weight of muscle” (Steven Vogel, Prime Mover: A Natural History of Muscle).

The function of muscles is to create pulling forces. So as a muscle contracts, a pulling force is applied to its attachment points. Whether or not this muscle succeeds in creating a pulling force (aka shortening) depends on the strength of the contraction versus the resistance it faces. This ‘shortening’ is called a concentric contraction.

Muscles also lengthen under contraction, which can be defined as an eccentric contraction. This occurs most commonly when our muscles are working against gravity.

For example, if you are placing a glass back on a table, gravity can bring your arm back to the table. But the musculature of the arm assist in opposing gravity just enough so the arm slowly lowers. Not only do muscles shorten (concentric) and lengthen (eccentric), they also contract isometrically to remain the same length to function as stabilizers.

Muscle Strains:

A strain is a disruption to the structure and function of the muscle. There are a number of ways to sustain a muscle strain:

  • The muscle gets stretched beyond the limits of its flexibility

  • The force exceeds the strength of the muscle

  • The duration of the force exceeds the endurance of the muscle

  • A direct impact to the area (contusion)

One of the most common mechanisms of injury is repetitive eccentric (lengthening) loading. This is because an eccentric contraction involves greater force and can lead to microscopic damage to the contractile portion of the muscle.

Moreover, muscles that cross two joints and contain a lot of type-II fast-twitch fibres are more commonly affected. This is why we see so many rectus femoris (quadriceps), hamstring and gastrocsnemius (calf) strains here at Ultra Sports Clinic.


As is the case with every condition, accurate diagnosis is key. Below is how a muscle strain is graded.

Grade I Muscle Strain: Symptomatic without functional impairment:

Consists of mild tenderness and mild pain. However, there is no loss of strength or range of motion. There is also no palpable defect or detectable swelling.

Grade II Muscle Strain: Symptomatic with moderate functional impairment:

Consists of moderate tenderness and pain. There is a mild to moderate loss of both strength and joint range of motion. There may be a palpable defect with detectable swelling present also.

Grade III: Symptomatic with significant functional impairment:

Consists of moderate to severe tenderness and pain. There is moderate to severe loss in both strength and range of motion. There is a palpable defect in the muscles with associated swelling, indicating a complete rupture of muscle fibres.

Image courtesy of Brukner and Khan


It’s believed that the human body is made up of approximately 360 joints. Stability of these joints depends on a number of structures. Ligaments, which connect bone to bone, play a vital role in joint stability.

Ligaments are made up of a short band of strong, flexible tissue. This tissue is made up of lots of individual fibres. There are approximately 900 ligaments in the human body and they function to decrease or even prevent certain movements altogether.

Ligament Sprains:

When a joint is stretched beyond the limits of its normal range of motion, ligaments are susceptible to sprain or tearing. This may lead to instability of the joint, which can result in pain or the onset of other pathologies.

As is the case with muscle strains, there are 3 grades of ligament injury:

Grade 1 Ligament Sprain:

A grade 1 ligament sprain involves only mild to moderate stretching of the ligament fibres. There is typically pain, mild tenderness and perhaps mild swelling. The joint range of motion is normal on ligament stress tests.

Grade 2 Ligament Sprain:

A grade 2 ligament sprain involves significant stretching of the ligament fibres. The symptoms of pain, tenderness and swelling are typically worse than in a grade 1. Ligament stress testing shows an increase in laxity but with an end point, suggesting there are still fibres in tact.

Grade 3 Ligament Sprain:

A grade 3 ligament sprain involves complete tearing of the ligament fibres. There is often more swelling than in grade I and II injuries. While the initial injury can be very painful, if the sensory fibres are divided than an individual can be pain free. Ligament stress testing shows a significant increase in laxity with no end point, suggesting all fibres have been disrupted.

Image courtesy of Brukner and Khan

What to do next?

One of Ultra Sports Clinic’s highly experienced physiotherapists can diagnose your condition with a thorough musculoskeletal examination.

Moreover, our Consultant Radiologist, Dr Rob Katz, can accurately diagnose your strain or sprain using our state of the art Ultrasound machine. If further imaging (such as MRI scan) is indicated, we can refer you to one of the many Consultants that Ultra Sports Clinic work with to ensure best possible outcomes.

Diagnosis is always key. To quote Mahatma Ghandi, “A correct diagnosis is three-fourths the remedy”.



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