Musculoskeletal disorder (MSD)

Every day, the musculoskeletal system is called upon to lift and carry objects, to sit, stand, walk, move and work. However, these tasks – or the way they are performed – sometimes require overexertion, which can cause pain and lead to a more serious injury known as a musculoskeletal disorder (MSD). Back pain, shoulder pain, tendinitis, bursitis, epicondylitis, lumbar sprain and herniated disc are some examples of MSDs.

The signs and symptoms of MSDs develop progressively through constant overexertion. They can be linked to work, sports, daily activities or age, and mainly affect the joints, muscles and tendons. Aches, discomfort and pain are the first symptoms of an MSD. These symptoms can worsen and, if left untreated, reduce quality of life.

• Discomfort or pain in a joint (while moving and at rest)
• Joint stiffness
• Localized fatigue (reduced muscular endurance and strength)
• Reduced range of motion, to the point of being unable to move
• Swelling
• Numbness
• Increased tenderness

MSDs are caused by actions that are frequent, repetitive and traumatic for the muscular and skeletal structures. For this reason they often occur during activities in the workplace, but they can also happen during sports and daily activities, at home or elsewhere.

• Repetitive movements, such as using a computer mouse
• Intense and continuous effort, such as lifting and moving heavy objects
• Working in an unsuitable environment, such as a poorly adapted workstation, or in cold, noisy or dimly lit conditions
• Awkward posture, such as bending or remaining immobile for long stretches of time
• Tasks that subject the joints to shock or vibration, such as using a jackhammer or sandblaster
• Stress

While initially benign, MSDs can become progressively worse. They generally go through three stages:

Any part of the body can be affected by an MSD, but some are affected more often than others. Here are the most common injuries.

Neck pain, or cervicalgia, has multiple causes (including whiplash, torticollis or osteoarthritis). It is often accompanied by stiffness that greatly restricts neck movement.

Neck pain may be felt in the upper body, especially in the back and shoulders. It is the affected tissue (vertebrae, tendons, ligaments, muscles or nerves) that determines the symptoms experienced.

The most common MSD affecting the shoulder joint is rotator cuff tendinopathy or bursitis. Rotator cuff tendinopathy is caused by overuse of a tendon. Poorly executed repetitive movements can result in injury to the tendons, thereby reducing their elasticity, and to the bursa.

Joints, along with related bones or tissues such as tendons, can be the source of elbow pain. There are two types of injury that affect the tendons of the elbow:

• Tennis elbow (lateral epicondylitis): pain on the outside of the forearm, near the elbow, in the epicondyle (bone protruding from the outer side of the humerus)
• Golfer’s elbow (medial epicondylitis): pain on the inside of the forearm in the epitrochlea (bone protruding from the inner side of the humerus)

Excessive, repetitive or sudden use of the wrist can lead to the following MSDs:

• Wrist tendonitis or de Quervain’s syndrome: inflammation of the wrist tendons
• Carpal tunnel syndrome: compression of the median nerve in the carpal tunnel, leading to tingling in the fingers and loss of muscle strength
• Guyon’s canal syndrome: compression of the ulnar nerve in the wrist
• Trigger finger
• Osteoarthritis

Cervical (neck) and dorsal (back) pain are very common reasons for seeking medical attention. Their frequency increases with age, affecting half of people over age 60. At work, back pain is a major cause of absenteeism. Neck and back pain are caused by wear and tear or injury to the spine.

The spinal column is made up of a series of bones called vertebrae, whose role is to provide strong yet flexible support for the upper body. The vertebrae also protect the very fragile spinal cord, which connects the brain to every part of the body through the nerves.

There are a total of 33 vertebrae along the spine, classified into five groups:

• 7 cervical vertebrae (C1 to C7)
• 12 thoracic vertebrae (T1 to T12)
• 5 lumbar vertebrae (L1 to L5)
• 5 fused sacral vertebrae (S1 to S5)
• 4 fused coccygeal vertebrae

Each vertebra consists of an oval part at the front (vertebral body) and a semicircular part at the back with processes, pedicles and joints (facets), as well as a spinous process that can be easily palpated or visualized.

Between the two parts lies the spinal canal, through which pass the nerve fibres that link the brain with the rest of the body. These nerves exit through spaces between the vertebrae (foramina), from the neck down to the junction between the last lumbar vertebra and the first sacral vertebra (L5-S1).

Each vertebra is separated from its neighbour by a shock-absorbing disc, which consists of a flexible core of gelatinous material inside a rigid shell (annulus).

A herniated (or slipped) disc occurs when the shell of a disc ruptures and some of the gelatinous core breaks out, resulting in painful contact with the nerve fibres. This injury can be caused by deterioration of the disc, age, trauma or an improper movement.

Most herniated discs happen in the lower back, in the lumbar region, leading to pain in this area. If the herniation compresses a root of the sciatic nerve, it may be accompanied by pain down one leg.

This injury is characterized by pain in the lower back (lumbar vertebrae L1-L5) or in the pelvis, sacrum or posterior. You may also feel pain in the thigh. Lumbar sprains are often caused by trauma, a fall or an improper movement. They can occur after stretching, rupturing or tearing the back muscles or ligaments, most often due to a sudden or abnormal movement of the joint.

Some people are at greater risk of developing this type of disorder, including those who are known to have lumbar instability or poor posture, or put heavy strain on their lower back in their everyday activities. Certain factors can also increase the risk of lumbar sprain, such as a sedentary lifestyle, pregnancy, excess weight and unhealthy habits.

The intervertebral disc gives the spine flexibility. If it is subjected to constant abnormal pressure, it can bend or rupture, causing severe pain as well as neurological problems, including loss of strength and numbness.

The sacroiliac joints connect the pelvic bones to the sacrum at the bottom of the spine. An improper movement, incorrect or prolonged posture, or excessive strain on the pelvis, can overload the lumbar spine and lead to tissue damage. This syndrome can also be caused by an injury, such as a fall on the buttocks, or tissue deterioration, often due to osteoarthritis. Pain usually occurs on one side only, in the lower back, buttock, groin and even the thigh.

The facet is a joint located behind the intervertebral discs and surrounded by a capsule. Pain is caused by deterioration or inflammation of the cartilage in the facet and capsule, and the ligaments surrounding them. This pain may be more intense at the end of the day, due to movement of the vertebrae and overuse of the joint. Usually, pain is felt in the central lumbar area and does not extend into the limbs.

The knee joint is complex and includes many components:

• Cartilage (enables the femur and tibia to slide over each other)
• Menisci (crescent-shaped; absorb shocks and stabilize the joint)
• Capsule (fibrous shell covering the joint and lined with a membrane that produces synovial fluid)
• Synovial bursae (membranous pockets filled with synovial fluid)
• Cruciate and collateral ligaments (stabilize the knee)
• Muscles, bones and tendons

The knee is the largest joint in the body. Its proper functioning is crucial to mobility and stability. During certain movements, such as climbing stairs, the knees support four to five times the body’s weight. Repetitive movements can easily damage them.

Knee pain can occur at any age and in any situation, even in athletes who are in excellent health. Here are some common symptoms:

• Acute pain when walking, standing for a long time, climbing or descending stairs, or kneeling (functional pain)
• Pain that wakes you up at night (inflammatory pain)
• Pain or fatigue in the legs
• Pain in the hips
• Locking
• Poor balance

Knee MSDs are associated with a variety of problems:

• Sprain (stretched ligament)
• Tendinopathies (or tendinitis)
• Lesions of the menisci
• Hygroma or bursitis of the knee (inflammation of the bursae, small pockets that enable the tendons to slide properly)
• Osteoarthritis
• Fractures
• Compression of the sciatic nerve (down the side of the calf)

• Patellofemoral syndrome: This disorder is defined as irritation and inflammation of the knee joint cartilage between the femur and the patella. Pain usually occurs following excessive use or stress on the joint, such as a rapid increase in the intensity of an activity.
• Iliotibial band friction syndrome: Pain usually occurs with repeated bending and stretching of the knee, such as while running or cycling. Irritation and inflammation are caused by two of the knee’s external structures repetitively rubbing against each other: the fibrous band on the outer thigh and a protrusion of the femur. Pain is felt on the anterolateral aspect of the knee.
• Knee bursitis: Bursitis is an inflammation of the bursa (the cushion containing the fluid that reduces friction between the bones, tendons and muscles of the knee). Frequent kneeling, falling on the knees and running are the main causes of bursitis.

MSDs are often diagnosed in a doctor’s office based on case history (type of pain, physical activity, description of the injury, etc.) supplemented by a physical examination (palpation, provoking the pain by extending and compressing the muscle, looking for signs of inflammation, etc.). These examinations are often sufficient to begin treatment.

Depending on the case’s complexity, the healthcare professional may use other diagnostic techniques:

Here we are referring to x-rays, magnetic resonance imaging (MRI) and ultrasound. An X-ray cannot always confirm a diagnosis, but can often help rule out other causes of pain (bone deformity, osteoarthritis, arthritis, etc.). An MRI is more suitable for detecting a problem in the bones and soft tissues (tendons, ligaments, cartilage, etc.). Ultrasound is increasingly used to identify abnormalities and inflammation in and around joints, as well as tearing or inflammation of tendons.

Blood tests are especially useful for confirming the severity of an inflammation (blood count, C-reactive protein (CRP), sedimentation rate). Other tests are used to confirm secondary causes (antibodies associated with arthritis or other disorders of the connective tissue or muscles, etc.).

In the event of pain in the large joints (knee and elbow), an examination of the fluid in the joint (synovial fluid) can be performed through a joint aspiration (arthrocentesis).

This technique, which involves recording electrical impulses in the muscles, makes it possible to verify whether nerve impulses are reaching the muscles, and to record electrical activity during muscle contraction and relaxation.

Surgery is rarely used to treat MSDs. However, it is indicated in some situations, such as treating carpal tunnel syndrome and certain spinal conditions.