Load and Capacity

All soft tissue injuries are a result of one thing: an imbalance between your body’s capacity and the load placed on it; specifically that load exceeds the body’s capacity.

With acute injuries the equation is simple. Broken bones, sprained ankles, and torn ligaments are examples of healthy tissue that is subject to a single-event high force load. The force is sufficient to damage the tissue and you end up with an acute, traumatic injury. In these situations you have normal capacity and excessive load over a short period of time. Injury results.

The next type of injury is when weakened tissue is subject to normal loads. This occurs when you are doing what you always do and sustain an injury.

This means that athletic pursuits, poor posture, and repetitive use at normal levels over time, can result in injury. The problem is there may be some gradual long standing problem that weakens the tissue. For example, 97% of Achilles tendon ruptures happen when the tissue is degenerated. This degeneration is sometimes completely unknown to the patient.

Think about it. Should performing a task that you always do really cause something to break? Only if that something is weakened. This is a “last straw” scenario. People are always trying to figure out what “caused” their injury. Some people really struggle with this until they realize it was not any one thing. If it wasn’t bending over that day it would have happened getting out of the car the next day. This is an example of normal load and decreased capacity.

Great. Decreased capacity is a real problem. What causes decreased capacity or weakened tissue?

The following disorders result in weakened tissue:
Adhesion/ Scar Tissue
Degeneration
Prolonged Inflammation
Steroid Injections

Diagnosis
A diagnosis is, generally, a convenient way to categorize a problem. Often when categorizing things, the individual elements get left behind for ease of categorization. The trouble is- in soft tissue problems, the individual elements are more important than the broad categorizations. Merely calling something iliotibial band (ITB) syndrome is a whole lot different than establishing the individual elements. The pain generator and contributing layers of dysfunction must be determined. Broad classifications can‘t be treated. Only specific individual problems or entities can be treated. Moreover, the diagnosis and treatment are constantly interwoven and evolving. As one element is identified and corrected, an additional element that is hiding underneath the first may present, necessitating a change in the direction and method of treatment.

For example, a person who experiences pain on the outside of the knee may have meniscus (cartilage in the knee joint) symptoms or irritation secondary to the meniscus being adhered to the collateral ligament. This prevents normal gliding and rotation of the meniscus, producing inflammation, jamming and popping. However that’s just getting started. The next questions is - why is there scar tissue between the meniscus and ligament? That scar tissue is a result of overload. For example, the ITB can be adhered to the quadriceps (muscle on front of the thigh). When this happens the ITB is unable to stabilize the knee. Then the question then becomes - how did the ITB become adhered to the quadriceps? This occurs because the quadricep is doing too much work. Why? Because the other leg has suffered a weakness or deficiency that forces the right quadriceps to compensate. When the patient runs ten miles, the left leg does seven miles of work and the right leg does thirteen. Only after these elements have been completely unlayered and corrected can a full and accurate diagnosis be established. What we really have is a series of provisional ideas that are tested and modified as treatment changes what we can see. The diagnosis is an evolving and ongoing process that only is complete when all the layers have been identified.

I stretch all the time but flexibility doesn’t improve. What’s the deal?
Stretching a healthy muscle will improve its flexibility. So if you’re stretching and haven’t increased in flexibility, you aren’t stretching a healthy muscle. The question then shifts to - What’s really wrong? The more fundamental question is - Why is the muscle tight? There are several reasons a muscle can be tight.

1. Pain: If a structure in the body is painful, the brain will tell muscles to contract taking pressure off the painful structure.

2. Nerve Entrapment: Nerves don’t stretch; they floss around and through structures. Nerves can become ‘glued’ to surrounding tissue preventing normal ranges of motion.

3. Adhesion / Scar Tissue: Adhesions prevent areas of muscle from stretching and contracting. This, of course, will limit muscle length.

4. Trigger Points: A trigger point is an area of focal muscle spasm and does not relax with regular stretching methods.

Effects of Scar Tissue
Pain free motion and posture depend upon properly functioning soft tissue. Muscles must be able to contract with appropriate force and timing as well as lengthen and stretch to perform effectively. Ligaments must be supple enough to allow for proper joint motion while not becoming too lax. Fascia must be smooth enough to allow structures to glide past one another. There is a great deal of interdependence of the soft tissues, as they serve similar functions. An injury to one structure will necessitate compensation. Properly functioning soft tissues support and protect joints, discs, menisci, and labrum. Scar tissue can compromise this protective function, leaving significant potential for injury and pain.

The effects of scar tissue in muscle are listed below.

1. Mechanical Limitation of Length

The area of scar will not lengthen as normal muscle does. This can result in a limited range of motion and change the axis of rotation of a joint. This is often the culprit in people who stretch all the time and don’t increase in flexibility.

2. Slow Speed of Elongation

Depending upon how flexible the actual scar tissue is, the muscle may reach full length. However, the time required to achieve full length is increased. This occurs because scar tissue has an increased coefficient of friction, essentially acting as a break. If the quadriceps contract at a normal speed and the hamstrings lengthen slowly they are more likely to tear.

3. Decrease Maximum Strength

The scar tissue and surrounding muscle fibers will not shorten when the muscle contracts. This can adversely affect strength simply by decreasing the amount of functional muscle. Secondary to a decrease in the amount of functional muscle, sub-maximal contractions will require a higher relative percentage of muscle fiber recruitment. This can result in earlier fatigue. Strength can also be limited by pain and/or by a malpositioned joint.

4. Slow Speed of Contraction

The speed of muscular contraction can be affected in two ways. First, as in elongation, the coefficient of friction is increased causing slower contraction. Second, contraction may be inhibited through the nervous system due to pain or improper joint position. Also when a muscle does not contract at the proper time, stability can be sacrificed resulting in excessive joint strain.

5. Muscular Hypertonicity

The areas where the scar tissue attaches to the healthy tissue (shown in red) can become irritated with use. This can cause the muscle fibers above and below the scar tissue (shown in blue) to go into protective contraction or “spasm,” called hypertonicity. This is often the case when people obtain temporary relief from massage or manipulation.

6. Pain

Scar tissue has been shown to have nociceptors (pain nerve endings) and, therefore, can produce pain. Depending upon how the scar affects function, pain can be felt at the site of scar, at the involved tendon attachment, or in the structure that must compensate for any deficiency.

7. Nerve Entrapment

Nerves travel through, under, and around other structures. Where they lie close to or travel through muscles, they can become entrapped. Nerves need to be able to slide past the muscles they are next to. This motion can be limited by the development of scar tissue. The scar effectively “glues” the nerve to the muscle, so when you move then nerve develops tension instead of sliding. This can cause weakness, numbness, pins and needles, burning, and aching sensations.

8. “Glue” Muscles Together

Virtually all muscle lie next to other muscles. They need to slide past one another to move efficiently. Figure 1 shows scar tissue adhering two forearm muscle together. This limits full range of motion and alters force vectors. These are among the most noticeable consequences of scar tissue.

No Inflammation
It is often believed that inflammation, usually in the form of “tendonitis” or “bursitis,” is the underlying process in most soft tissue injuries. Over the last decade this assumption has been successfully challenged. Leadbetter et al. reported “Overuse injuries have one striking characteristic, inflammatory cell infiltration seems to be aborted or absent. Nirschl reports “Histologic examination of the tissues resected from pathologic tendons often fails to reveal inflammatory cells, and instead shows a consistent pattern of a hypoxic degenerative process. These pathologic changes are the same whether the rotator cuff, patellar tendon, Achilles tendon, plantar fascia, or wrist extensors are involved. In the face of considerable histologic and pathologic, a recent review article by Khan et al. in the Physician and Sports Medicine reported “Physicians must acknowledge that the cause is most often due to tendinosis, rather than tendonitis, and treat the problem using a fundamentally different paradigm,” recommending that overuse injuries are to be assumed to be non-inflammatory. It has become clear that inflammatory conditions occur much less frequently than previously thought and are common only in tear or crush injuries, not in overuse disorders. A change in the pathology of overuse disorders requires a change in treatment strategies.

I feel better when I cut back on my activity level. When I increase my activity my symptoms get worse again.

We call this the pain-rest-pain treadmill. You feel well and are active. Pain shows up forcing you to cut back. Then you feel better and increase your activity again. Then symptoms show up and you are forced to cut back again. Sometimes, with each turn of this cycle less activity is required for the symptoms to show up. Rest is not solving your problem, but rather, taking stress off of it. Only very specific soft tissue problems actually heal with rest.

My injuries usually go away with rest but this one is not.

Your old injuries likely did not really go away. When you have a painful problem your body will change the way you use certain muscles. This shifts the load off of the injured area and onto a healthy area. So the problem feels like it is gone. After a while, the healthy area that has to pick up the slack for the injured area will breakdown and become injured. This will result in a new symptom. This can keep happening until there is no real healthy tissue left for the load to shift too. At this point you have an injury that can seem like no big deal but does not really improve with rest and is very sensitive to use. Metaphorically speaking your “well has gone dry” and have one symptom but lots of problems.

When we take a history, we hear lots of injuries the patient has had before but “went away.” On examination we often these areas to be damaged and very relevant to correcting their current symptom.