Pain is inevitable in sport. The ability to push through pain can lead to championship titles, whilst persisting pain can be career destroying. As a physiotherapist it is essential to understand the complex phenomenon of pain in order to facilitate rehabilitation.
The standard model and diagnostic dilemma
The ‘standard model’ of the brain, on which the last century of neurology bases its thinking, describes the brain as a large number of highly specialised, autonomous modules that interact little with each other and are hardwired from birth (Ramachandran, 2005). In alliance with the ‘standard model’ is the direct-line theory of pain, which explains pain as direct transmission from pain receptors in the body to a pain centre in the brain (Melzack, 2005). For example, a footballer pulls a hamstring resulting in direct transmission of painful stimuli sent to the brain.
One problem with the direct line theory is that MRI studies do not show a direct relationship between tissue damage and experience of pain. For example, MRI results that demonstrate severe disc degeneration often do not correlate with lower back pain. Furthermore 40 % of patients with ‘normal’ MRI results complain of back pain (Rothstein, 1998). Likewise, the damage shown by ultrasound results of athletes with patella tendinitis (jumper’s knee) does not directly correlate to the degree of pain experienced by the athlete (Cook et al, 2001).
This does not mean that identifying the injured structure is not important or that it is not crucially involved in your pain. But looking to tissue damage alone to explain the relationship between pain and sporting performance is not sufficient.
Multidimensional theory of pain
The neuromatrix model defines pain as a multidimensional experience produced by the integration of various neural networks. In order to make sense of the information the pain neuromatrix has four major components that determine the sensory output of pain. The first is the input of various stimuli from the environment including movement and sensory information. In the second, the input travels up the neural pathway to the brain where stimuli from the environment is integrated with a range of information including the athletes emotions, memories, cognition and attention to form a characteristic pattern, known as the ‘neurosignature’ (Melzack, 2005). The third component is the process of converting the ‘neurosignature’ into self-awareness and the fourth is the output stimulus of pain.
The multidimensional theory of pain can explain why a rugby player can continue to play with a broken thumb in competition and not be hampered by pain. However, once the game is over, attention is drawn to the pain. The ‘neurosignature’ changes pre-post competition, as does the athlete’s perception of pain.
Is pain useful?
Following an acute injury, such as an ankle sprain, the area quickly becomes inflamed. The inflammatory process marks the beginning of the healing process, which is crucial as without inflammation healing does not occur. The chemical changes caused by inflammation can sensitize the peripheral nerves and this sensitization can cause once pain free stimuli such as light touch/pressure to feel painful. The inflammatory process normally lasts between 3 days to 2 weeks, depending on the tissue. Pain perceived during this process can be considered as useful as usually it forces an athlete to rest the injured body part, preventing further damage as the tissue heals. The entire healing process from inflammation to tissue repair and remodelling of fibres will take normally up to 3 months. After this, period pain perception is no longer useful as there is no longer a risk of causing actual damage to the healed tissue.
Sometimes the brain/nervous system can continue to transmit pain beyond the acute, ‘helpful’ period ie when there is no longer any tissue damage. This pain is called persistent or chronic pain. In chronic pain, pain receptors (nocioceptors) in the affected area become sensitised and respond to non-harmful stimulus such as normal movements. If the nerves are very over-sensitive they may even send pain signals in the absence of any stimulus. The spinal cord which transmits the pain to the brain can also become sensitised and the brain continues to perceive there is a real threat of danger to the tissues although they have healed.
How to manage your athlete’s symptoms
To ultimately address the relationship between pain and sport it is necessary to consider all the contributing variables/factors that feed into the athletes ‘neuromatrix’ and if their pain is acute (helpful) or chronic. Particularly important for managing cases of chronic pain, the physiotherapist needs to think about ways to help the athlete desensitise the brain/nervous system. Moving back to the ‘neuromatrix’ model the physiotherapist needs to appreciate various variables such as the athlete’s emotions, cognition and previous experiences in order to understand what variables are contributing to the increased sensitivity of the nervous system. For example, pain can be made worse if you are feeling stressed, worried or have people telling you that you should not be moving as you will cause further injury. Whilst manual therapy and exercise rehabilitation can help in some ways to desensitise the affected body areas, the physiotherapist should think more widely to include all contributing factors that may be feeding into the athlete’s pain.