Muscles are designed to use a lot of energy and thus need constant blood supply and access to oxygen. So when we have a muscle sprain or strain it heals fast because it has direct access to oxygen and blood that brings all the healing factors to the muscle.
Tendons however by design use 7.5 times less oxygen than muscles. The tendons job is to transmit force from muscle to bone. Essentially tendon attach muscle to bone and when muscles contract it pulls on the tendon which then pulls on the bone to move.
The benefit of tendons needing less oxygen means it can carry loads and maintain tension for long periods of time without risking cell death due to blood cut off. This is helpful because we can use our tendons day to day with no problems, it’s when the tendon is injured that the problem arises. The problem is that is takes much longer to heal than we like.
So what is the timeline for healing from an acute tendon injury?
Phase 1:
Inflammatory phase: red blood cells and inflammatory cells rush into the area. In the first 24 hours you have special cells that come in: white blood cells that kill any germs and eliminate infected or damaged cells. So the white blood cells are essentially the clean-up crew that has to take away damaged issue and ensure no infection occurs, which would delay the healing process or result in complications.
While that is happening special chemicals are released by the body into the injured area to improve blood flow by creating new blood vessels, which will help to bring in supplies for rebuilding the tissue. This is important because in the injury blood vessels would have been damaged and blood would be leaked around the tissue (like causing an internal bruise). Those old damaged blood vessels with coagulate to stop the bleeding, so new vessels are needed.
Phase 2:
After a few days remodelling begins where Type 3 collagen is laid down, as if to cover the open wound. It’s the scab that starts to form on cut.
Phase 3:
After about 6 weeks, the modeling phase begins which is made up of 2 phases:
Phase 1: Starts around 6 weeks and ends 10 weeks: in this phase the new tissue that has been laid down become more fibrous (meaning more stiff and thick).
Phase 2: After 10 weeks the maturation phase begins where the fibrous tissue become more scar tissue like and this can last up to 1 year.
Treatment focuses on various phases to healing:
Phase 1:
Pain and inflammation management. While rest in the early couple days is recommended, resting too long can lead to stiffness, decreased range of motion and scar tissue thickening, which can lead to more pain. So we start first with teaching you about the injury, ways to manage pain and inflammation and ways to begin moving the area safely. Pain and inflammation can be present throughout the entire healing process to varying degrees and so we need good strategies to manage that as we move through the phases of treatment and healing. Pain and inflammation is a natural part of the healing process and is meant to be a guide to let us know that we are exercises the right area and with enough intensity, as well as protector, to make sure we don’t over-do it. This phase can last 2-3 weeks and usually begins to incorporate phase 2 relatively quickly.
Phase 2:
Working on range of motion, simultaneously managing pain and support flexibility in the scar tissue. This phase than last 4-12 weeks depending on the severity of the injury. Not working on range of motion can result in limited movements in all directions or some. This can impact our activities of daily living. As range of motion is improving, there will likely be a blend of phase 3 in the time frame.
Phase 3:
muscle activation which begins to support remodeling because the scar tissue will remodel along the lines of tension (a phase that should not be missed). Repetitive healthy loading, as in exercise promotes healing and long term function of that tendon. If we skip exercising the tendon it will start to break down, the new cells will degredate and you will loss tendon structure. This means the tendon will be smaller, weaker, less felxibile and more likely to become re-injured and if re-injured can be more severe. If you exercise this promotes the cells to build more collagen than can be remodelled for restoring normal function and strength. This phase typically begins at some point along phase 2 and can continue for 4-12 weeks.
Phase 4:
Muscle Loading, Coordination and neuromuscular control: The tendon needs to be stressed intense enough to support the maturation of the scar tissue and ensuring proper re-integration to day to day activities. Once range of motion and relative strength is restored then comes the phase of really getting the tendon to work, especially if you have a repetitive or heavy physical job. This phase is important for restoring optimized structure and function to the tendon to reduce risks of re-injury. This phase can be anywhere from 4-8 weeks.
So all in all, depending on the level of tendon injury typical treatment time is anywhere from 3 months to sometimes 6-9 months.
Reference:
Andarawais-Puri et al. 2015. Tendon basic science: development, repair, regeneration and healing. Journal of Orthopedic research. June edition.
Sharma, P and Maffulli, N. 2016. Biology of tendon injury: healing, modeling and remodeling. Journal of Musculoskelet Neuonal Interact 6(2): 181-190.