Not all calf strains are the same….
Calf strains, whilst common, do not occur as often as injuries to the hamstring.
However, when they do occur they are often associated with a disproportionately longer recovery time when compared with other muscle injuries.
Despite this, research on calf injury management is limited, especially when compared to muscles groups such as the hamstrings.
In this blog we will break down what we do know about calf injuries and how they occur.
What Are The Calf Muscles
The work “calf” refers to a group of muscles at the back of the shin. Depending on individual anatomy the calf is actually comprised of 2 or 3 muscles. These are called the gastrocnemius, soleus and plantaris.
The calf muscles have different makeups and different functions. The gastocnemus muscles are made of many fast twitch muscles fibres and so are better designed for rapid, powerful contractions.
In contrast, the soleus is made up of slower twitch muscle fibres and better suited for postural control. Not everybody has a plantaris muscle (it is absent in 7-20% of people) but it is best thought of as assisting the gastrocnemius in its function.
Because the calf muscles are suited to different activities they are commonly injured in different ways.
Gastrocnemius Strain
Injuries to the gastrocnemius commonly occur when the knee is straight and the ankle begins to move from a toes up to toes pointed downwards position rapidly. This mechanism places the muscle into a stretched position under load.
This injury commonly occurs from maximal sprinting or acceleration and will have a sudden onset. The individual may hear an audible popping noise. With higher grade injuries there will be an immediate weakness and pain with pointing the toes down. Walking may be difficult or impossible.
Strains of the gastrocnemius normally occur at to either inside head of the muscle or at the junction between the muscle and tendon (musculotendinous junction).
Strains of the gastrocnemius share an identical mechanism to tears of the achilles tendon (which require an immediate diagnosis and appropriate management for good outcomes).
It is therefore very important to have any high energy calf injury immediately screened by a competent physiotherapist or other health care professional experienced in these type of injuries.
Soleus Strain
Soleus strains are more likely to occur from repetitive movement of the toes towards the knee with the knee bent. This puts the muscle into a repetitive stretched position.
This injury commonly occurs from distance running, especially if lots of inclines are involved. Because these are a repetitive injury they rarely come on suddenly, being much more likely to have a gradual onset. An affected person may feel a gradual onset of tightness and aching. There may not be any associated muscle weakness.
Strains to the soleus can be difficult to pick up, as these symptoms can be present in other conditions such as sciatica, general muscle tightness or even DVT’s (blood clots) in the calf region.
Severity of Injury
The severity of calf injury can be graded.
Using the “British Athletic Classification” of muscle strain we can grade strains in severity 1 through 4 with subclassifications in each of these catagories.
But, to keep it simple……..
Grade 1 (Mild) Strains
Those sustaining this type of injury may not actually notice whilst participating in sport, or may initially feel a slight niggle.
Very small tear of less than 10% of muscle fibres. There is typically no decrease in muscle strength, pain and tenderness may not be immediately apparent. There will be no associated swelling or bruising.
Grade 2 (Moderate) Strains
Those sustaining this type of injury will immediately notice a grabbing sensation in the calf muscle. They are likely not to be able to continue playing.
Significant tear of 10-50% of the muscle fibres OR involvement of the musculotendinosus junction. There will be significant immediate pain with this type of injury. Moderate swelling and some bruising may be present. There will be a loss of range of motion and strength.
Grade 3 (Severe) Strains
Those sustaining this type of injury are immediately likely to fall to the ground. There will be no chance of continuing to play.
I constitute a significant tear of more than 50% of the muscle .There will be severe loss of muscle strength with significant bruising and swelling.
Grade 4 Complete Tears
Those sustaining this type of injury are immediately likely to fall to the ground. There will be no chance of continuing to play.
These constitute a complete rupture of the muscle . There may be a palpable gap in the muscle. There will be severe loss of muscle strength with significant bruising and swelling in the days following the injury.
Risk Factors for Calf Strain
From our current limited evidence base it appears that unlike other muscle strains the largest risk factors for calf strain are actually unmodifiable. These factors are;
Age - It has been proposed that reductions in muscle quality, power output and rate of force development as we age are responsible for an increase in risk. Though we actually currently have no evidence showing that training these variable will reduce risk of injury!
Previous lower limb injury - Previous strain of the hamstring, adductor, quadricep or calf or previous injury of the knee increase the risk of calf injury.
Current research suggests that height, weight, sex and dominant side have no correlation!