Common MSK Disorders PDF

# Common MSK Disorders ## Introduction - The first and perhaps most important thing to understand is that common musculoskeletal problems associated with physical activities and sports are **injuries**, not diseases, and are caused by **mechanical violence**. - Every injury involves structural **ti...

# Common MSK Disorders ## Introduction - The first and perhaps most important thing to understand is that common musculoskeletal problems associated with physical activities and sports are **injuries**, not diseases, and are caused by **mechanical violence**. - Every injury involves structural **tissue failure**, even at a microscopic level - Tissues have a psyche that can be irritated. When a tissue is damaged, it is not just irritated, it is **damaged**, and it needs to be **respected** in order to heal. ## Injuries not Diseases - **Inflammation** is a **healthy response to trauma** and is a **necessary component of healing**. - It **should** **not** be suppressed with anti-inflammatory medication. - Post-traumatic inflammation **does not linger** and **lasts several weeks at most**. ## Chronic MSK Problems - Chronic MSK problems are not inflammatory diseases, they are injuries. ## Repetitive Loading - Remember that tissues **need to recover** from overload or near overload. - This recovery includes **visco-elastic recovery** between repetitions and **cellular recovery** between sessions. ### Recovery between Reps - If deformed visco-elastic tissue isn't allowed to return to its neutral position between applications of load, deformation will accumulate. - Each subsequent repetition of the same magnitude of load may deform it further. - This results in the tissue's strength (magnitude of load required for failure) being lower under sufficiently frequent repetitive loading. - In general, the load required for failure decreases as a function of repetitions without recovery. - When assessing or discussing someone's strength in the weight room, we may refer to their "1 rep max" or "5 rep max" in a particular exercise. - We could use similar language for tissue strength denoting its "1 rep strength" (load that causes failure if applied once) or its "100 rep strength" (load that causes failure if applied 100 times in succession, sufficiently rapidly that the tissue is not allowed to recover visco-elastically between reps). ### Recovery Between Session - This is a different issue, one we'll examine more closely in Module 3. ## Classify Trauma by Reps Required for Failure - Trauma is classified by how many repetitions of violence were required to cause an injury, even though few people recognize that repetitive trauma is exactly that. - What is always recognized as "trauma" is single-repetition violence. - Damage caused by repetitive violence is often inappropriately dismissed as "overuse". - The key is to understand that it's still trauma (mechanical violence), just that it was meted out more slowly! ## Acute Trauma - Acute trauma is **injury caused by a single repetition of mechanical violence**. - It may be more than one rep such as a flurry of punches, collisions or decelerations in rapid succession- we would still call the injury or injuries resulting from such a flurry of violence "acute trauma". - Acute trauma is classified or graded by severity. ### Grades of Acute Trauma - Historically, the most frequently used terms were 1st, 2nd, and 3rd - degree in reference to slight-partial, moderate-partial, and complete failure of issues respectively. - Since the advent of more advanced medical imaging such as MRI, these terms have fallen somewhat out of favor, in part became radiologists cannot define any objective criterion that differentiates 1st and 2nd degree failure. - Some injuries that result in catastrophic dysfunction (e.g. severe joint instability) nonetheless appear to have some tissue hanging on in images, such that they are not actually "complete" or "3rd degree", but might as well be. We will treat such nearly complete injuries as if they are "done like dinner" (a quote made famous by former Toronto Maple Leaf "Tiger" Williams). - This has led to the increasing adoption of more functionally useful terms for describing the severity of acute trauma: - **High-grade trauma** - any degree of tissue failure associated with significant **mechanical insufficiency** of the injured structure. - The insufficiency could be observed as weakness, instability, spatial gap, etc. the injured tissue cannot do its job. - **Low-grade trauma** - lesser degrees of tissue failure not associated with significant mechanical insufficiency. - It may hurt but the injured tissue can still do its job. ### Types of Acute Trauma - Although engineers use the language of deformation mechanics universally, health care professionals tend not to. - **Strain** is normalized deformation in engineering science. - Health care pros reserve the word "strain" for tensile injuries of muscle. - **Fracture** is any type of complete structural failure in engineering science. - Health care reserves the word "fracture" for harder tissues, and a ruptured muscle isn't referred to as "fractured", even though is technically speaking. ## Bone and Teeth - These hard tissues have special terms for tissue failure. - **Complete failure** is called **fracture** regardless of the type of loading. - **Partial failure** has multiple names, depending on its extent: - If a partial failure can be seen on planar x-rays or CT scan, it is called an **incomplete fracture**, **partial fracture** or **hairline fracture**. - If it cannot be seen on x-ray or CT, but can be seen on MRI , it is called one of several names: **bone stress**, **bone contusion**, **bone bruise** or **microfracture**. ## Muscle-Tendon-Bone Units - Injuries to "muscles" occur mostly at the junctions in the series of tissues - either the muscle-tendon junction (myotendon), or the bone-tendon junction. - Injuries are described on the basis of the type of loading causing injury: - **Failure caused by tensile loading** is called a **strain**. If it's high grade, it's referred to as a **tear** or **rupture**. - **Failure caused by compressive loading** is called a **contusion** (or bruise). ## Ligaments and Joint Capsule - Injuries of ligaments and joint capsules are described on the basis of the type of loading causing injury, with the following difference: - **Failure caused by tensile loading** is called a **sprain**. If it's high grade, it's referred to as a **tear** or **rupture**. - **Failure caused by compressive loading** is called a **contusion** (or bruise). ## Cartilage - Cartilage is very dense but still soft connective tissue. - It is not normally mineralized, and injuries of cartilage are described using the language applied to both bones and softer tissues, depending on circumstances. - We may refer to cartilage as being torn, fractured, ruptured, strained or bruised. - The term bruised is usually inappropriate. ## Repetitive Micro-Trauma ### "Overuse" and Tissue Degeneration - Chronic disorders in SEM are the result of two things: - **Repetitive micro-violence** - **Insufficient healing response** - These are referred to in a variety of ways: - "Overuse" injuries - "Degenerative" conditions - "Chronic" injuries - The key is to understand that these are injuries (tissue failure caused by mechanical violence), and the reason they do not heal are sometimes complex or even unknown, but usually involve one issue that is within our control: **undesirable repetitive loading**. ## Joint Surface Degeneration - Gradual degradation of the hyaline cartilage in our synovial joints is a ubiquitous problem. - Everyone will suffer to some extent if they live long enough. - There are different causes of cartilage failure and not all of them are injuries. - The diseases that cause **joint inflammation** and **tissue destruction via inflammation** are properly called **arthritis**. - They are not commonly seen in SEM, as they are not in any way caused by physical activity. - They are typically inflammatory disorders of **auto-immune origin**: - Rheumatoid arthritis - Psoriatic arthritis - Anklyosing spondylitis - Reiter's Syndrome - Arthritis associated with lupus erythematosis - These are not our concern here. - Degeneration of joint surface cartilage that is not primarily caused by inflammation has historically been called **osteoarthritis**. - However, over the last 50 years, it has become clear that this is not a single homogeneous disorder but a **group of disorders of different causes** that result in the same thing - **loss of joint surface cartilage**. - We now prefer to reserve the term osteoarthritis for one of them and call the other disorders by other names: - **Idiopathic diffuse osteoarthritis** - Disease of unknown origin, probably at least partly genetic in which the hyaline cartilage in multiple joints, including small joints in the hand such as the PIPJs, degenerate symmetrically (left and right sides) without significant overloading. - The involved joints are not inflamed initially, but can become so in late stages. - It can result in severe joint destruction and disability. - **Post-traumatic arthrosis** - Many injured joints lose some of their cartilage 5-15 years after they were initially injured. - We believe that this is because of injury to the bone underneath the cartilage - **micro-fracturing** sustained during joint instability that heals but results in less delivery of nutrients to the overlying cartilage, bringing about its demise gradually. - **Cumulative micro-traumatic arthrosis** - Often, the cartilage in a major load-bearing synovial joint is damaged in microscopic increments by hundreds or thousands of tiny failures. - The degradation of cartilage proceeds through stages involving **micro-fissures**, **partial erosion**, and **full-thickness ulceration**. ## Entheso-Tendonopathies - As noted earlier, the tensile injuries to muscle-tendon-bone units tend to occur at the junctions of the different tissues in the chain - either the muscle-tendon junction (myotendon), or the bone-tendon junction (enthes or enthesis). - Injuries to tendons and their entheses are called **entheso-tendonopathies**. - Injuries of the enthes per se are called **enthesopathy**. - They are the most common. - Injuries of a tendon per se are called **tendonopathy**. - They are less common. - When they do occur, it is typically in a relatively avascular portion of the tendon. - These are not inflammatory conditions. - There is no such thing as "tendinitis" and we avoid use of this term. - These are injuries, typically micro-scopic in the beginning, that **do not heal**. ### The Usual Sequence of Events Unfolds in This Way: - **Micro-failure** - the enthes or tendon is torn at some level (possibly microscopic, or low-grade macroscopic injury) by excessive tension, almost always during lengthening activation of the attached muscle, when it is being used to decelerate motion. - **Failure of healing** - the injured enthes or tendon fails to heal during its period of spontaneous healing, typically for one or both of two reasons: - **Continued overloading** - The injured person fails to perceive that they are significantly injured and they continue to overload the enthes or tendon, which is easier to injure because of its reduced strength. - **Poorly healing tissue** - Entheses and tendons are slow to heal at the best of times, and portions of them often injured may have relatively poor blood supplies, impairing their healing ability further. - **Tissue degeneration** - the unhealed tissue does not respond to loading properly, and degenerates, which means that the extra-cellular matrix becomes abnormal in some way. - Typically, collagen fibres are less cross-bridged, there is water between them and there is more mucin mixed in, which is called mucoid degeneration. - **Further injury** - because the degenerate tissue is structurally weak, it is easily further injured by repetitive loading. Rinse and repeat, we have a problem. ## Dysfunction - Dysfunction is any manifestation of disorder, something is not working properly. - It is possible to have disorder without pathological anatomy, and we use the word dysfunction to denote disorders without structural cause. - Examples include: - Muscle imbalances/asymmetries - Weakness caused by inactivity - Neurovascular compression caused by poor posture - Others