03 Jun What You Need To Know About Tissue Healing
When an individual sustains an injury, one of the first questions asked is, “How long will it take until I am back to normal?” When an unexpected event such as an injury disrupts our quality of life, naturally we want to return to our full functional capacity as soon as possible. The difficult part of injuries is that there are certain components of them we are unable to control, such as our 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 optimize healing times by avoiding factors that could slow the normal healing process. In this article, we will discuss what body tissue is, the normal phases of tissue healing, why various tissues heal differently, and what you need to know about tissue healing after an injury!
Tissue Healing Basics: What Is Body Tissue?
Learn what you need to know about tissue healing and you will better understand injuries and how the body heals! Body 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 organized into four separate categories: epithelial, connective, muscle, and nervous. Epithelial tissue is what covers the outer surfaces of our body, such as our skin. Connective tissue is what brings cells together to enhance protection and support, such as bone or tendon. Muscle tissue is what contracts in response to a stimulus, allowing us to move. Nervous tissue, including the brain, spinal cord, and other nerves, work together as a team to assist in communication between various regions of our body. As humans perform different movements and activities throughout their lives, these different tissues will adapt to the various physical stresses that are placed upon them. This theory of tissue adaptation to physical stress is well explained in an article by Mueller and Maluf 2002, that will further help you understand what you need to know about tissue healing¹.
What Are The Phases Of Tissue Healing?
Tissue healing is classified into 3 phases: inflammatory, proliferative, and the remodeling (maturation) phase. There is a lack of a unanimous definition regarding the duration of these three phases throughout the literature. Moreover, tissue healing a process that can be viewed as a continuum, with overlapping timeframes throughout the entirety. Regardless, each tissue type will follow the same, systematic pattern of healing, yet the amount of time spent in each phase may vary depending on the type of injury. Gaining a general understanding in reference to the staging of the healing process will allow you to further conceptualize what you need to know about tissue healing.
Inflammatory Phase (Day 0 – Day 6): You may have a visual memory of when you or someone had an injury and immediately became swollen around that specific area. This is the first part of the tissue healing process, known as the inflammatory phase. Bleeding occurs due to widening in blood vessels, known as dilation, and a release of a chemical called histamine, which eventually allows other cells that help with healing, such as white blood cells, to enter the damaged area. Moreover, the arrival of these healing cells consumes and remove dead tissue. This process is relatively short-lived, lasting from the day of injury until about day six after the injury.
Proliferation Phase (Day 4 – Day 24): The second phase of tissue healing is known as the proliferative phase. Cells including fibroblasts surround the damaged tissue and place new, immature layers of tissue in a random fashion that is derived from a specific type of collagen: type III. Collagen is an important protein that provides 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 normal, healthy tissue.
Remodeling Phase (Day 21- 2 years): The last phase of tissue healing consists of immature type III collagen being converted into a more mature type of collagen: Type I. One analogy for the concept of immature versus mature collagen is thinking about cooked versus uncooked spaghetti. When you have an injury, the immature, type 3 collagen that is first applied in the proliferative phase is like cooked spaghetti on a plate, disorganized, and each strand of the spaghetti running in different directions. In contrast, the type I, mature collagen is like uncooked spaghetti out of the box, each strand looking the exact same, running in a parallel fashion. Often times, you may hear the term scar tissue, which refers to this new healthy tissue that replaces injured tissue overtime. This remodeling phase starts from day 21 and can last for up to two years depending on the injury.
Timelines For Tissue Healing Based On Tissue Type
One important factor regarding what you need to know about tissue healing after an injury is the type of tissue that is injured. For example, a bone stress fracture will heal differently than a meniscus tear. This is because of two concepts: blood supply, and the biological make-up of the tissue. Having good blood supply or being highly vascularized is very important for tissue growth and remodeling after an injury. As evident on the depiction below, a severe sprain to a ligament, such as the anterior cruciate ligament (ACL), may take longer to heal than a bone fracture due to the high amount of blood supply and simple structure of bone versus the inadequate blood supply and more complex make-up of the ACL. By simply being provided the information to know that some tissues may take longer to heal than others will provide you with insight and more clarity if you experience a particular injury!
Basics Of Optimizing Health During Each Tissue Healing Phase
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, followed by early mobilization, and eventually optimal loading with an eventual return to full, functional capacity. As stated previously, the time spent in each of these phases as well as the specific actions you may be taking will be different depending on the type of injury you may have. An important aspect of what you need to know about tissue healing is not only understanding the basic phases of tissue healing, but also the actions YOU must take in order to optimize your outcomes after an injury! We highlight this below:
Inflammatory Phase: Immediately after an injury, swelling and pain is expected, which both can be combated with ice and anti-inflammatories. Your job in this phase is to minimize aggravating activities to the particular tissue that was injured, decrease swelling and pain in the area, and prepare the body for the next stage of the healing process. For example, a cast applied to an ankle fracture or an immobilizer brace after an ACL reconstruction both provide protection to these injured tissues respectively. The protection of the damaged site at this time allows cells to enter injured tissue and initiate the healing process without disruption. Timeframes for the application of ice, certain medications, and rest can vary as well as the evidence to support these methods is conflicted in the literature. An article by Vavken 2018 discusses the positive, short-term benefits of anti-inflammatories and ice for tissue healing². More on this to come in a future post!
Inflammatory Phase –> Proliferative Phase: Here you will transition from rest and protection to early mobilization and optimal loading. An article by Bleakley et al discusses the concept of POLICE, which stands for protection, optimal loading, ice, compression, and elevation³. The key portion of this acronym is optimal loading, which is exchanging rest with a balanced and progressive treatment plan where early activity encourages quicker recovery. A loading scheme should imitate the distinctive mechanical stresses placed upon the injured tissue during functional activities, which can differ between tissue type and anatomical region. An example of optimal loading after a total knee replacement is performing knee extension exercises, which mimic the controlled extension of the knee joint needs as you place your foot down when walking.
Proliferative Phase –> Maturation Phase: During this final transition, you will begin to progress towards movements that simulate activities that you do on a daily basis, ultimately returning you to your prior level of function. For instance, if you are returning to recreational running, you may begin a walk/run program, and other 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. An example of exercising in the maturation phase is exemplified by our return to plyometrics exercises!
Similar to when the body has to fight off an infection or a cough, it does the same for tissue injuries. Understanding the systematic course that the body takes as well as the variability in healing times based on tissue type will help you not only gain more insight about your injury, but also give you the confidence to take ownership of your healing process. A proper evaluation, diagnosis, and treatment plan from a trained, healthcare professional is the first step to take after a tissue injury to ensure that accurate information is provided and that you have the best chance of maximizing your outcomes! Take autonomy of your injuries by learning what you need to know about tissue healing!
About The Author
Sherif Elnaggar, PT, DPT, OCS
Sherif graduated from Temple University with a Bachelor’s of Science Degree and a concentration in Kinesiology. He then received his Doctorate of Physical Therapy Degree from DeSales University, graduating with honors of the professional excellence award and research excellence award. After his graduate studies, he served as Chief Resident of the St. Luke’s Orthopedic Physical Therapy Residency Program. Sherif is an active member of the American Physical Therapy Association (APTA), is an APTA Credentialed Clinical Instructor, and is a Board Certified Orthopedic Clinical Specialist. Sherif focuses on understanding how movement impairments are affecting function while also promoting lifestyle changes in order to prevent recurrences of injury. His early treatment interests include running-related injuries, adolescent sports rehab, and ACL rehab in lower extremity athletes. He also has been involved in performance training for youth soccer players. Outside of working as a physical therapist, he enjoys traveling, running and cycling, following Philadelphia sports teams, and spending time with his family.
- Mueller MJ, Maluf KS. Tissue Adaptation to Physical Stress: A Proposed “Physical Stress Theory” to Guide Physical Therapist Practice, Education, and Research. Physical Therapy. 2002;82(4):383-403. doi:10.1093/ptj/82.4.383.
- Bleakley CM. PRICE needs updating, should we call the POLICE? South African Journal of Sports Medicine. 2016;25(1). doi:10.17159/2413-3108/2013/v25i1a463.
- Vavken P. Evidence-based Treatment of Muscle Injuries. Swiss Sports & Exercise Medicine. 2018;66(1):16-21. doi:10.34045/ssem/2018/2.