Soleus muscle injuries can often be difficult to diagnose
Although calf muscle injuries are frequent in football, injuries to the soleus, in particular, can be difficult to treat...
The question most frequently asked is “What makes the soleus muscle so susceptible to repeated injury?”
Let’s make a start by reviewing the basic anatomy. The calf group is made up of three muscles, often referred to as the ‘Triceps Surae’, and these comprise of the gastrocnemius, soleus, and plantaris muscles.
Together, they blend to form the Achilles tendon. The most commonly injured of all three muscles is the gastrocnemius, which is the superficial bulky muscle that gives the calf its characteristic shape.
The soleus muscle lies deeper and lower than the gastrocnemius, originating behind its lower fibres. The third muscle that comprises the trio is known as the plantaris muscle, and this is a deeper muscle running along the posterior aspect of the tibia.
Academics agree that the plantaris muscle is rarely involved in calf injuries (Armfield et al, 2006).
The soleus muscle is an important muscle for ankle strength. It has a predominance of slow-twitch fibres thus biasing its function towards power, and the soleus also acts as a postural muscle. It, therefore, influences lower limb biomechanics and gait.
Consequently, if any dysfunction occurs in the ankle or foot, the potential exists for the soleus to be affected (or vice versa); which may present as a recurrent injury depending on the underlying cause.
Calf strains are common in football as we know and with the lower limb accounting for 92% of injuries sustained (Ekstrand et al, 2011) then it’s hardly surprising that these will arise time and again.
The key factor, however, between recovering from strains of the superficial gastrocnemius muscle and the deeper soleus lies in establishing the true extent of the injury.
Soleus muscle strains or tears are more difficult to assess than gastrocnemius injuries and a full MRI scan is required to provide the most accurate images of the damaged tissue (Balius et al, 2014).
The disadvantage with MRI scanning though is that the scans are performed with the muscle at rest. Ultrasound scanning, which is the preferred modality for more superficial injuries, can be adapted to provide a dynamic, moving image of an injured muscle which can be viewed in real-time.
But due to the depth of the soleus muscle, there are areas where dynamic ultrasound is simply unable to provide an accurate enough image to allow clear visualisation of the tissue damage sustained.
Therefore, in recovering a soleus muscle injury, it may well be that the true extent of the tissue damage cannot be wholly defined. Dixon (2009) reported that injuries to the soleus muscle can often be underestimated due to the generally sub-acute nature of their clinical presentation.
In football, this usually shows as the injured player reporting some gradually increasing discomfort throughout ranging from a few days to several weeks as opposed to an obvious strain resulting from one single, specific incident.
The player will report that the calf “feels tight” and that the discomfort is “always there”. As the soleus muscle is a deeper, power-based muscle which influences a player's gait, any underlying weakness or incomplete healing may not be evident until higher-level activities are resumed.
This leads to localised discomfort and the likelihood that the process of repeated injury is already well underway. Thus, the classic presentation of a soleus muscle injury is one of pain and stiffness with gradually worsening symptoms over time.
Pedret et al (2015) found that injuries to different areas of the soleus muscle responded to treatment at different rates. It is thought that injuries occurring in the central tendon of the soleus muscle where it blends with the Achilles tendon have a longer recovery time than injuries to the medial or lateral aspects of the muscle.
We know that the body doesn’t repair injured tissues with a like-for-like substance and that the healing process in muscular tears/strains is through the laying down of scar tissue. This inevitably affects flexibility and strength to some degree, likely leading to biomechanical imbalances as a result.
Recurrent or repeated injuries are often the product of such muscular imbalances and if one leg is taking the strain slightly more than the other or in a slightly different way, then any structure which has been injured will be susceptible to further injury if it hasn’t healed correctly before returning to play.
An earlier study by Koulouris et al (2007) suggested that deep strains of the soleus muscle could potentially lead to associated strains of the gastrocnemius muscle; likely as a result of an imbalance in biomechanical loads on the calf and lower limb complex as a whole.
There are a couple of likely options when trying to define why repeated soleus injuries occur. This might be a biomechanical issue directly related to the way a player runs, or whether the foot posture is affecting the calf muscles to the extent that they are overloading in the lower calf when running, for example.
If this is the case then no amount of rest will help in the long term; since the incorrect loading will gradually be repeated as the player increases his or her activity and the same symptoms are likely to recur once again.
However, current available evidence would suggest that the soleus muscle also requires longer healing time than other muscles in the calf; due to its deep-seated location and involvement in lower-limb posture.
So if it’s simply a case of coming back too early before complete healing has had the chance to take place, then the same thing applies.
The most important aspect of the whole rehab process for any medical team is going to be to determine why soleus muscle injuries are prone to recurrence.
Perhaps the answer lies in the symptoms; which are low level initially, progressive, difficult to isolate and often show no actual definitive site of injury in the early stages.
That suggests that athletes returning to play in these circumstances following a soleus strain might not be ready. If a recurrence of injury subsequently arises, then without over-simplifying things, perhaps a more intensive examination is required before they are cleared to play.