Acute Stage, Post-Acute Stage and Chronic Stage of Sinew Injuries

Acute Stage, Post-Acute Stage and Chronic Stage of Sinew Injuries

It doesn’t matter what area of the body is involved, an injury goes through three main stages of healing - acute, post-acute, and chronic. Far too often a person suffers an injury, rested until the injured area feels better, but then found that pain returns when normal activity is resumed. In many cases, this is because the injured person does not know what to do and when to do it. In each stage of an injury healing, there are different processes going on inside the body and different activities that are appropriate for each stage.


Aside from the risk of re-injuring a partially healed body part, improperly and partially healed injuries can result in a lifetime of pain and discomfort. Furthermore, the weakness and immobility of improperly healed injuries can encourage future injury to bones, joints, cartilage, tendons, and muscles that are forced to take up the “slack.” To prevent such from happening, there should be awareness of the processes and appropriate actions for each stage of healing.

The Acute Stage: What Happens?

The acute stage of healing may also be referred to as the inflammatory stage. It occurs immediately after the injury takes place and will continue for around three to four days. The main process is inflammation, but much is taking place during these first few days.

The injury will generally cause localized pain, spasms, swelling, and redness to the injured area. These symptoms of injury will be most severe during this stage. The inflammation process is a natural response and serves to protect the injured area, release chemicals to assist with pain, neutralize toxins, and prepare damaged tissues for the repair process. Macrophages are hard at work clearing out the debris and creating a setting suitable for the regeneration of new tissue that will take place in the near future.

The inflammatory response is important, but it should be carefully monitored since studies have shown prolonged inflammation can stall or stop the healing process.

Amazingly, scar tissue also begins to form during the acute stage of healing. While scar tissue is vital to healing and recovery, too much or improperly formed scar tissue can slow the healing process down and be the cause of future re-injuries.

What Should The Injured Person Be Doing During The Acute Stage?

Most experts agree that rest is best. Gentle movements and some light physical therapy exercises might be beneficial, but this greatly depends on the location and severity of the injury.

The Post-Acute Stage: What Happens?

During day 4 through 21 post-injury, the body is going through the post-acute stage of healing. The inflammation process will gradually decrease, but pain, especially at the end of range of motion, may still be a factor in some injuries.

Scar tissue continues to grow. New growth of capillaries bring a fresh supply of blood and connective tissue starts to form. This process, called angiogenesis or revascularization, is key to repairing the damaged area.

However, the tissues remain extremely fragile and easily damageable. Limited activity and exercise during this stage may cause muscle weakness.

What Should The Injured Person Be Doing During The Post-Acute Stage?

Since tissue is so fragile, much care must be placed on not performing any activity that could damage the new growth. If this tissue is damaged, the pain may be very intense and the injury might return to the acute stage. So, experts recommend the injured person start with gentle movements that aren’t stressing and continue to limit unnecessary activity. Toward the end of the stage, intensity and duration of movement and activity may be increased as tolerated. At this point, mild isometric exercise could help to strengthen the damaged area. These low-intensity exercises can help address any muscle weakness from inactivity as well. Stretching exercises may also be beneficial.

The Chronic Stage: What Happens?

Day 21 post-injury marks the beginning of the chronic stage of injury healing or reconstruction phase. Notice that there isn’t an end date; this is because reconstruction may last for weeks to years. It all depends on the injured area and degree of injury. Some severe injuries can require years of therapeutic exercise regiments to make a full recovery.

In any event, this stage consists of true injury healing as the body is remodeling scar tissue based on the stress applied to it. Scar tissue has now bound itself to the damaged soft tissue fibers and spurred them to draw together for repair. How this takes place is vital, as bulky masses of scar tissue can surround the injury site. Scar tissue is less flexible, weaker, and has a tendency to deform surrounding tissue. If this happens, the injured muscle, tendon, ligament, etc. has lost a lot of flexibility and strength and might be more prone to re-injury. Pain related to the injury has greatly subsided and is usually only present when activity involves the far end of range of motion or overusing the injured area.

What Should The Injured Person Be Doing During The Chronic Stage?

Engaging in appropriate activities and exercises greatly impacts scar tissue strength and formation, as scar tissue remodeling is determined by the stress placed on it. If done correctly, scar tissue can be very useful in protecting the injured area. If not, it can be instrumental in prolonged healing and risk of re-injury. The injured person must take an active role in adhering to recommended home exercise and physical and occupational therapy designed to rehabilitate and strengthen the injured area.