Back to Basics: Revising Tissue Healing

Boston Bruins goaltender Jeremy Swayman looks to make a save during the second period against the Buffalo Sabres at KeyBank Center. Mandatory Credit: Timothy T. Ludwig-Imagn Images

Historically, musculoskeletal injuries have been linked to pain caused by tissue damage, assuming that the intensity and severity of pain are directly proportional to the extent of the damage. Therefore, pain was believed to decrease as the injured tissues healed. However, even acute pain is more complex than this traditional perspective suggests, and advancements in pain science have challenged this view.

Practitioners increasingly recognize that the pain experience is multifaceted and individual. It involves many factors, including the type of injured tissue, peripheral neuropathic processes, immune response, brain processing, psychosocial influences, peripheral and central nervous system sensitization, neuroplasticity, and endogenous mechanisms⁽¹⁾.  

Acute Pain

Acute pain plays a very important role in sports injuries. It forces the athlete to stop, preventing further damage to already injured tissues. The clinician’s role is to manage the athlete’s pain, provide the optimal environment for healing, and return the athlete to sport at the appropriate time with the most robust tissue repair possible. 

Education and gradual loading are key to rehab, and a thorough understanding of pain mechanisms and healing physiology is essential. Initially, a thorough interview will provide insight. The mechanism of injury, the type of trauma, contributing factors, severity and injury grade, and the tissue type provide valuable information that impacts the athlete’s management.

Acute pain is a neural-biochemical response to tissue damage. It involves the activation of nociceptors, the sensory receptors that respond to injury. The acute pain mechanism is activated when an external stimulus activates a nociceptor. The nociceptor transduces the stimulus into an electrical impulse, which travels along the peripheral nerve to the spinal cord and is processed and potentially modulated by descending pathways. The impulse then ascends to the brain through the thalamus and is interpreted before generating a response. This response travels back through the spinal cord and the peripheral motor nerves.

Various factors, including the tissue type, the extent of the injury, and the athlete’s emotional state, can influence the input, processing, and output mechanisms. Sports-related pain and injury have a multifaceted effect on the athlete. For example, there may be a pervasive fear of re-injury and social isolation. The desire to return to sport is facilitated through motivation and support⁽²⁾. Time spent explaining pain pathways is hugely beneficial to healing and compliance in athletes⁽³⁾. 

“Practitioners increasingly recognize that the pain experience is multifaceted and individual.”

Practitioners must thoroughly understand the phases of healing and pain mechanisms. Backed by science, they can gain the athlete’s confidence, impacting compliance and active engagement in their rehab process. The four phases of healing include hemostasis (bleeding), inflammation, repair (proliferation), and remodeling (see figure 1). The healing process is a continuum, and there is considerable overlap between these three phases.

They involve a cascade of events triggered by chemical mediators in the blood, resulting in a process that varies in length depending on the injury severity. Many factors delay or interrupt this process. Intrinsic factors like systemic medical conditions such as insulin-dependent diabetes mellitus (IDDM) and extrinsic factors like insufficient or inappropriate rehabilitation. It is the practitioner’s responsibility to ensure an optimal environment for the healing process to occur. This involves an accurate sports injury assessment and a large component of athlete education. 

Practitioners must guide a graduated return to activity by repeatedly reassessing to avoid re-injury. Soft tissue healing involves a complex interaction between the injured tissues, the vascular system, and chemical mediators to promote damage control, revascularization, and the formation of connective tissue. Inflammation is a healthy, normal, and required local response to injury that destroys or inactivates foreign invaders and sets the stage for tissue repair.