Tendons are remarkably strong structures that connect your muscles to your bones. They transmit muscle force to create movement. However, when a tendon becomes painful, many people think it is irreversibly damaged. Here's the good news: tendons constantly adapt to the loads placed on them. Contrary to the myth of wear and tear, gradual and well-balanced loading strengthens tendons rather than weakening them. This guide explores what tendons really are, how they work, and why they have a remarkable capacity for healing.

What is a tendon and what does it do?

A tendon is a band of strong fibrous tissue that connects a muscle to a bone. It transmits the force generated by the muscle to the bone to create joint movement. Tendons enable your muscles to move your joints efficiently.

Tendons act like transmission cables in your body. When a muscle contracts, it pulls on the tendon. The tendon then pulls on the bone. This system allows your muscles to create precise movements.

Let's take your shoulder as an example. The rotator cuff tendons connect four muscles to the arm bone. When these muscles contract, their tendons pull on the bone. This creates the rotation and elevation of your arm. Without these tendons, your muscles would not be able to create movement.

Tendons also have elastic properties. They store and release energy, much like a rubber band. This property improves the efficiency of movement and reduces the amount of muscle work required.

How are tendons structured?

Tendons are composed of collagen fibers aligned parallel to each other. These fibers are organized into tight bundles, giving them exceptional strength. Tendons also contain specialized cells and a blood supply that support their function.

Collagen is an extremely strong structural protein. The fibers align in the direction of the forces that the tendon must withstand. It's like the strands in a rope. This organization allows the tendon to withstand heavy loads without breaking.

Tendons contain cells called tenocytes. These cells produce and maintain collagen. They repair daily microdamage. They enable the tendon to adapt to changing demands.

The blood supply to tendons varies depending on their location. Some areas receive a lot of blood. Others receive less. This difference explains why some tendons heal more slowly. Blood carries the nutrients needed for healing.

Why do tendons become painful?

Tendons become painful when the load placed on them exceeds their capacity to adapt. This overload can result from too rapid an increase in activity, excessive repetitive movements, or prolonged periods of rest followed by intense activity without progression.

The simple formula is: load > capacity = tendon problem.

This overload can occur in several ways. A rapid increase in activity is a common cause. For example, you start swimming three times a week when you haven't swum for months. Your tendons haven't had time to adapt. They become painful.

Paradoxically, prolonged rest can also create problems. When you are inactive for several weeks, your tendons adapt to this reduced load. Their capacity decreases. If you then resume intense activity without progression, even normal loads can exceed this reduced capacity.

It is crucial to understand that tendon pain does not mean serious structural damage. In most cases, the tendon is not torn or broken. It is temporarily overloaded. This distinction changes the approach to treatment.

What is the difference between tendinopathy and tendinitis?

Tendinopathy is the modern term used to describe any tendon problem. Tendinitis specifically involves inflammation. Research shows that most chronic tendon pain is not inflammatory but degenerative. Hence the use of the term tendinopathy.

For a long time, it was believed that all tendon problems were caused by inflammation. The suffix "itis" means inflammation. Treatments focused on reducing inflammation: rest, ice, anti-inflammatory drugs.

However, microscopic studies revealed something surprising. In most chronic cases, there was no significant inflammation. Instead, researchers observed degenerative changes. Collagen fibers that were normally well aligned became disorganized.

This discovery changed our understanding. Most chronic pain is not caused by inflammation but by degenerative tendinopathies. The term tendinopathy is more accurate.

This distinction influences treatment. If the problem is inflammatory, rest makes sense. If the problem is degenerative with collagen disorganization, the solution is different. The tendon needs progressive loads to stimulate collagen remodeling.

How do tendons heal?

Tendons heal slowly in a phased process: initial inflammation (a few days), cell proliferation (a few weeks), and collagen remodeling (several months). This process requires gradual mechanical loading to stimulate the alignment of new fibers.

The inflammatory phase lasts 1 to 7 days. Immune cells clean up debris. This phase prepares the body for healing.

The proliferative phase follows. The tenocytes multiply. They produce new collagen to replace the damaged fibers. This new collagen is initially disorganized. The fibers are oriented in all directions.

The remodeling phase is the longest and most critical. It lasts from 3 months to 1 year or more. The disorganized collagen must reorganize itself. The fibers must align themselves in the direction of the forces. The tendon must regain its strength.

Remodeling requires mechanical stimulation. Collagen fibers align in response to forces. Without progressive loading, collagen remains disorganized. The tendon remains weak. This is why complete rest is rarely the optimal solution.

What is load management?

Load management is the art of adjusting the intensity and volume of activities to keep the load within the tendon's capacity. It allows the tendon to gradually adapt and strengthen without aggravating the pain.

Remember: load > capacity = problem.

Load management addresses both aspects. On the one hand, it temporarily reduces the load. On the other hand, it gradually increases the tendon's capacity through carefully measured loading.

The traditional approach would be complete rest. This reduces the load. The pain decreases. But the tendon's capacity does not increase. It may even decrease with deconditioning. When you resume activity, the problem returns.

The modern approach is different. You temporarily reduce the intensity to a level that your tendon can tolerate. At this level, the tendon is loaded but not overloaded. It can adapt. After a few weeks, its capacity increases. You can then gradually increase the intensity.

This progression should be guided by symptoms. A slight increase in pain during activity is acceptable. But if the pain persists for more than 24 hours afterward or increases day by day, you have exceeded your current capacity.

Why is rest alone not enough?

Rest alone temporarily reduces pain by eliminating the load. However, it does not increase the tendon's capacity. Prolonged rest can even reduce this capacity. As a result, when you resume your activities, the tendon is no better prepared and the pain returns.

Complete rest creates several problems. First, it provides no stimulus for collagen remodeling. Fibers must align in response to forces. Without load, they remain disorganized.

Secondly, prolonged rest leads to deconditioning. Your tendons adapt to the absence of load. Their capacity decreases. Just two weeks of immobilization significantly reduces their mechanical properties.

Third, rest does not address the factors that caused the problem. If your tendinopathy is the result of muscle weakness or a dysfunctional movement pattern, rest will not correct anything. When you resume your activities, these factors will still be present.

This does not mean that you should ignore the pain. Temporary modification is part of load management. But this modification should be a smart reduction, not a complete elimination.

How does progressive loading help?

Progressive loading stimulates tenocytes to produce new collagen and align it in the direction of the forces. This stimulation gradually increases the tendon's capacity. Progressive strengthening exercises create a stronger and more resistant tendon.

Exercise programs generally follow a phased progression.

This progression takes time. Generally, a minimum of 12 to 16 weeks. Sometimes longer. Research shows success rates of 70% to 90%. This is comparable to or higher than more invasive procedures, without the risks.

Do tendons really wear out with age?

No, contrary to the myth of wear and tear, tendons do not wear out like mechanical parts. Tendons are living tissue that constantly remodel themselves. Aging slightly reduces their ability to adapt, but appropriate loading keeps them healthy.

The myth of wear and tear persists everywhere. "Your tendons wear out with age." These statements seem logical. After all, mechanical parts wear out with repeated use.

But your body is not a machine. Biological tissues work differently. Your tendons are constantly repairing themselves. Every day, your tenocytes break down old collagen and produce new collagen. This renewal allows for adaptation. If you impose a reasonable load, they adapt and strengthen.

Studies on athletes demonstrate this. These individuals place enormous strain on their bodies for years. If the wear and tear model were correct, all veteran athletes would have destroyed tendons. This is not the case.

Aging affects tendons. Collagen production slows down slightly. Blood flow decreases a little. But these changes do not spell doom for your tendons. They simply mean that progress must be more gradual.

Even older people can strengthen their tendons with appropriate training. The ability to adapt never disappears. It only slows down.

The real problem is not wear and tear from overuse. It is deconditioning from underuse. Tendons that are not loaded weaken. A deconditioned tendon cannot tolerate normal loads. It becomes painful during simple activities.

Instead of protecting your tendons by using them less, you should keep them strong by loading them regularly and progressively. Proper use protects your tendons. Inactivity weakens them.

To learn more about how to apply these principles to specific shoulder conditions, check out our comprehensive guide to rotator cuff tendinopathy. If you suffer from calcific tendinitis, our detailed article on this condition explains why calcium deposits do not mean that your tendon is permanently damaged. To understand how physical therapy can help you apply these principles of progressive loading, explore our guide to physical therapy for shoulder pain.

Your tendons are resilient. They have a remarkable ability to adapt and heal. With the right approach (temporary reduction, then gradual guided increase), most problems resolve completely. Your tendons are stronger than you think.