When we suffer an injury, one of the first questions I get asked is “how long will it take until I am back to normal? “ 

We want to return to our full functional capacity as soon as possible but the difficult part of injuries is that there are certain components that we are unable to control, age, the type of tissue that was injured, the blood supply to a specific tissue and the extent of damage that was done. However, what we can control is enhancing our understanding of tissue healing, and how to optimise healing times by avoiding factors that could slow the normal process. In this blog, we will discuss what body tissue is, the normal phases of tissue healing, why various tissues heal differently and how to optimise your healing time after an injury!

What does the term tissue mean?

Tissue is a collection of similar cells that are found together within the human body. There is a vast quantity of cell types throughout the body however they generally are organised into four separate categories; 

  1. epithelial – covers outer surfaces of our body such as the skin. 
  2. connective – brings cells together to enhance protection and support eg tendon
  3. muscle – contracts in response to a stimulus and allows us to move 
  4. nervous – works together to assist in communication between various regions of our body.  

As humans perform different movements and activities throughout their lives, these different tissues with adapt to the various physical stresses placed upon them. 

What are the phases of healing?

We classify tissue healing into three phases: the inflammatory, proliferative, and the remodelling or maturation face. It is a continuum with overlapping timeframes throughout the process. Each tissue type will follow the same systematic pattern of healing, the time spent in each phase will be dependent on the type of injury. 

Inflammatory phases (day 0 – day 6) 

If you are anyone you know has suffered an injury before and the area has become swollen this is the first part of the tissue healing process, known as the inflammatory phase. 

Bleeding occurs due to widening in the blood vessels (known as dilation) and a release of a chemical called histamine. This allows other cells that help with healing such as white blood cells to enter the damaged area. The arrival of these healing cells consumes and remove dead tissue. This process is relatively short lived, lasting from the day of injury until approximately day 6 after the injury. 

Proliferation phases (day 4 – day 24)

The second phase of tissue healing is known as the proliferative phase. Cells surround the damaged tissue and placed new immature layers of tissue in a random fashion that is derived from a specific type of collagen. Collagen is important protein that provide structure to your body. It is during the proliferative phase that the tissue not only begins to reduce in size, but is also weak, as type III collagen does not have the same tissue properties as a normal healthy tissue. 

Remodelling phases (day 21-2 years)

The last phase of tissue healing consist of immature type III collagen being converted into a type I collagen which is more mature. An analogy for the concept of immature versus mature collagen is cooked versus uncooked spaghetti.  When you have an injury, the immature type III collagen and that is first applied in the proliferation phase is like cooked spaghetti on a plate, disorganised and each strand running in different directions. In contrast, the type I collagen is uncooked spaghetti when it is coming out of the box, each strand looking the exact same, running in a parallel fashion. The term scar tissue refers to this new healthy tissue that replaces injured tissue over time. 

The remodelling phase starts from day 21 and can last for up to 2 years depending on the injury. 

Timelines for tissue healing based on tissue type 

An important factor regarding timelines for healing after an injury is which type of tissue has been injured. For example a bone stress fracture will heal differently to a meniscal tear. This is due to 2 main reasons: 

  1. The blood supply – having a good blood supply is important for tissue growth and remodelling after an injury. 
  2. The biological structure of the tissue injured. 

Ligaments such as an anterior cruciate ligament will take longer to heal than a bone fracture due to the high amount of blood supply and simple structure of bone versus inadequate blood supply and a more complex structure of the ACL.

Basics of optimising health during each phase of tissue healing

Progressing from the inflammatory phase to the maturation phase of tissue healing begins with a short period of rest and protection of the injured site, this is then followed by some early mobilisation and optimal loading of the tissues with an eventual goal of returning to full functional capacity.

As mentioned earlier, the duration of these phases as well as the specific actions you may be taking will differ depending on the type of injury you may have suffered.

Inflammatory phase: 

Immediately after an injury, swelling and pain is expected. Both can be treated with ice and anti-inflammatories. The most important goal of this phase is to avoid aggravating activities to the tissue that has been injured, decrease the swelling and the pain in the area and prepare the body for the next phase of healing. Examples would include a cast which has been applied to an ankle fracture or a brace applied to a ligament injury. The protection of the injured tissue allows the cells to enter and initiate the healing process without disruption.

Inflammatory – proliferation phase:

At this stage, there is a transition from rest and protection to early mobilisation and optimal loading. The concept POLICE standing for Protection, Optimal Loading, Ice, Compression and Elevation is now used in acute injury management. The key part is optimal loading, which is exchanging rest with a balanced and progressive treatment plan where early activity encourages quicker recovery. A gradual exposure to load imitates the distinctive mechanical stresses placed upon the injured tissue during function activities which differs between tissue-type and anatomical region. An example of optimal loading after a total knee replacement is performing the extension exercises which mimics the controlled extension the knee joint needs as you place your foot down during walking.

Proliferation – maturation: 

During this final transition between phases, progression towards movements that simulate activities undertaken on a daily basis, ultimately returning to your prior level of function. For example, if returning to recreational running, walk/run program maybe programmed with running specific exercises. The appropriate stress you apply to your body progressively during these phases allows the new mature collagen to form around the injury over time. 

In conclusion

Similarly to when the body has to fight off infection or a cough, it does the same for tissue injuries. 

Understanding the systematic course that the body takes as well as variability and healing times based on tissue type will help you understand your injury. 

A proper evaluation, diagnosis and treatment plan by a physiotherapist is the first step to take after a tissue injury to ensure that not only do you get accurate information but also the best chance of maximising your outcomes and returning to full function as soon as possible.