Musculoskeletal disorders (MSDs) are injuries or pain in the human musculoskeletal system, including the joints, ligaments, muscles, nerves, tendons, and structures that support limbs, neck and back. MSDs can arise from a sudden exertion (e.g., lifting a heavy object), or they can arise from making the same motions repeatedly repetitive strain, or from repeated exposure to force, vibration, or awkward posture. Injuries and pain in the musculoskeletal system caused by acute traumatic events like a car accident or fall are not considered musculoskeletal disorders. MSDs can affect many different parts of the body including upper and lower back, neck, shoulders and extremities (arms, legs, feet, and hands). Examples of MSDs include carpal tunnel syndrome, epicondylitis, tendinitis, back pain, tension neck syndrome, and hand-arm vibration syndrome.

MSDs can arise from the interaction of physical factors with ergonomic, psychological, social, and occupational factors.

Most cases of back pain are related to issues in human musculoskeletal system and are not related to severe diseases. Musculoskeletal problems also called mechanical because many of them linked to vertebrae physical motions. Back pain itself is not considered a diagnosis, but rather a symptom of underlying (in most cases musculoskeletal) problems.

following:

- Vertebrae misalignment, which can cause nerve interference (also called subluxation), muscle tension, or muscle spasm

- Strained muscles

- Sprained ligaments

- Ruptured disks, which also called "slipped", or herniated disks

- Degenerative discs (lose their cushioning ability). The degeneration usually caused by repetitive strain, or injury, or aging.

- Irritated joints

Some examples of symptoms experienced by patients with RSI are aching, pulsing pain, tingling and extremity weakness, initially presenting with intermittent discomfort and then, with a higher degree of frequency.

A repetitive strain injury (RSI) is an "injury to the musculoskeletal and nervous systems that may be caused by repetitive tasks, forceful exertions, vibrations, mechanical compression, or sustained or awkward positions".

Musculoskeletal injury (MI, not to be confused with myocardial infarction) refers to damage of muscular or skeletal systems, which is usually due to a strenuous activity. In one study, roughly 25% of approximately 6300 adults received a musculoskeletal injury of some sort within 12 months—of which 83% were activity-related. MI spans into a large variety of medical specialties including orthopedic surgery (with diseases such as arthritis requiring surgery), sports medicine, emergency medicine (acute presentations of joint and muscular pain) and rheumatology (in rheumatological diseases that affect joints such as rheumatoid arthritis). In many cases, during the healing period after a musculoskeletal injury, a period in which the healing area will be completely immobile, a cast-induced muscle atrophy can occur. Routine sessions of physiotherapy after the cast is removed can help return strength in limp muscles or tendons. Alternately, there exist different methods of electrical stimulation of the immobile muscles which can be induced by a device placed underneath a cast, helping prevent atrophies

Symptoms are pain at the radial side of the wrist, spasms, tenderness, occasional burning sensation in the hand, and swelling over the thumb side of the wrist, and difficulty gripping with the affected side of the hand. The onset is often gradual. Pain is made worse by movement of the thumb and wrist, and may radiate to the thumb or the forearm.

In the common presentation of acute low back pain, pain develops after movements that involve lifting, twisting, or forward-bending. The symptoms may start soon after the movements or upon waking up the following morning. The description of the symptoms may range from tenderness at a particular point to diffuse pain. It may or may not worsen with certain movements, such as raising a leg, or positions, such as sitting or standing. Pain radiating down the legs (known as sciatica) may be present. The first experience of acute low back pain is typically between the ages of 20 and 40. This is often a person's first reason to see a medical professional as an adult. Recurrent episodes occur in more than half of people with the repeated episodes being generally more painful than the first.

Other problems may occur along with low back pain. Chronic low back pain is associated with sleep problems, including a greater amount of time needed to fall asleep, disturbances during sleep, a shorter duration of sleep, and less satisfaction with sleep. In addition, a majority of those with chronic low back pain show symptoms of depression or anxiety.

De Quervain syndrome, is a tenosynovitis of the sheath or tunnel that surrounds two tendons that control movement of the thumb.

Low back pain is not a specific disease but rather a complaint that may be caused by a large number of underlying problems of varying levels of seriousness. The majority of LBP does not have a clear cause but is believed to be the result of non-serious muscle or skeletal issues such as sprains or strains. Obesity, smoking, weight gain during pregnancy, stress, poor physical condition, poor posture and poor sleeping position may also contribute to low back pain. A full list of possible causes includes many less common conditions. Physical causes may include osteoarthritis, degeneration of the discs between the vertebrae or a spinal disc herniation, broken vertebra(e) (such as from osteoporosis) or, rarely, an infection or tumor of the spine.

Women may have acute low back pain from medical conditions affecting the female reproductive system, including endometriosis, ovarian cysts, ovarian cancer, or uterine fibroids. Nearly half of all pregnant women report pain in the lower back or sacral area during pregnancy, due to changes in their posture and center of gravity causing muscle and ligament strain.

Low back pain can be broadly classified into four main categories:

- Musculoskeletal - mechanical (including muscle strain, muscle spasm, or osteoarthritis); herniated nucleus pulposus, herniated disk; spinal stenosis; or compression fracture

- Inflammatory - HLA-B27 associated arthritis including ankylosing spondylitis, reactive arthritis, psoriatic arthritis, and inflammatory bowel disease

- Malignancy - bone metastasis from lung, breast, prostate, thyroid, among others

- Infectious - osteomyelitis; abscess

4

Tendinopathy refers to a disease of a tendon. The clinical presentation includes tenderness on palpation and pain, often when exercising or with movement.

Three terms have evolved in the medical terminology to refer to injuries that cause tendon pain:

- Tendinitis - acute tendon injury accompanied by inflammation

- Tendinosis - chronic tendon injury with degeneration at the cellular level and no inflammation

- Paratenonitis - Inflammation of the outer layer of the tendon (paratenon) alone, whether or not the paratenon is lined by synovium

- Paratenonitis with tendinosis - Paratenonitis associated with intratendinous degeneration

- Tendinopathy - chronic tendon injury with no implication about etiology

Tendon injuries arise from a combination of intrinsic and extrinsic factors; acute tendon injuries may be predominantly caused by extrinsic factors, whereas in overuse syndromes as in the case of tendinopathy it may be caused by multifactorial combinations of both intrinsic and extrinsic factors. An example of an intrinsic factor for tendinopathies are: poor biomechanics such as limb malalignments and hyperpronation that may cause increased traction loads acting on the foot and ankle that may increase the incidence of Achilles, flexor hallucis longus muscle, and tibialis posterior muscle tendinopathies.

Persons suffering from peripheral neuropathy experience numbness and tingling in their hands and feet. This can cause ambulation impairment, such as trouble climbing stairs or maintaining balance. Gait abnormality is also common in persons with nervous system problems such as cauda equina syndrome, multiple sclerosis, Parkinson's disease, Alzheimer's disease, myasthenia gravis, normal pressure hydrocephalus, and Charcot–Marie–Tooth disease. Research has shown that neurological gait abnormalities are associated with an increased risk of falls in older adults.

Orthopedic corrective treatments may also manifest into gait abnormality, such as lower extremity amputation, post-fracture, and arthroplasty (joint replacement). Difficulty in ambulation that results from chemotherapy is generally temporary in nature, though recovery times of six months to a year are common. Likewise, difficulty in walking due to arthritis or joint pains (antalgic gait) sometimes resolves spontaneously once the pain is gone. Hemiplegic persons have circumduction gait and those with cerebral palsy often have scissoring gait.

A combination of postural changes, the growing baby, unstable pelvic joints under the influence of pregnancy hormones, and changes in the centre of gravity can all add to the varying degrees of pain or discomfort. In some cases it can come on suddenly or following a fall, sudden abduction of the thighs (opening too wide too quickly) or an action that has strained the joint.

PGP can begin as early as the first trimester of pregnancy. Pain is usually felt low down over the symphyseal joint, and this area may be extremely tender to the touch. Pain may also be felt in the hips, groin and lower abdomen and can radiate down the inner thighs. Women suffering from PGP may begin to waddle or shuffle, and may be aware of an audible clicking sound coming from the pelvis. PGP can develop slowly during pregnancy, gradually gaining in severity as the pregnancy progresses.

During pregnancy and postpartum, the symphyseal gap can be felt moving or straining when walking, climbing stairs or turning over in bed; these activities can be difficult or even impossible. The pain may remain static, e.g., in one place such as the front of the pelvis, producing the feeling of having been kicked; in other cases it may start in one area and move to other areas. It is also possible that a woman may experience a combination of symptoms.

Any weight bearing activity has the potential of aggravating an already unstable pelvis, producing symptoms that may limit the ability of the woman to carry out many daily activities. She may experience pain involving movements such as dressing, getting in and out of the bath, rolling in bed, climbing the stairs or sexual activity. Pain may also be present when lifting, carrying, pushing or pulling.

The symptoms (and their severity) experienced by women with PGP vary, but include:

- Present swelling and/or inflammation over joint.

- Difficulty lifting leg.

- Pain pulling legs apart.

- Inability to stand on one leg.

- Inability to transfer weight through pelvis and legs.

- Pain in hips and/or restriction of hip movement.

- Transferred nerve pain down leg.

- Can be associated with bladder and/or bowel dysfunction.

- A feeling of the symphysis pubis giving way.

- Stooped back when standing.

- Malalignment of pelvic and/or back joints.

- Struggle to sit or stand.

- Pain may also radiate down the inner thighs.

- Waddling or shuffling gait.

- Audible ‘clicking’ sound coming from the pelvis.

Musicians experience a number of health problems related to the practice and performance of music.

Pain or tenderness to palpation usually occurs on the sides of the sternum, affects multiple ribs, and is often worsened with coughing, deep breathing, or physical activity. On physical examination, a physician inspects and feels the patient for swollen or tender areas, and can often produce the pain of costochondritis by moving the patient's rib cage or arms.

A factor that may aid in the differentiation of costochondritis from Tietze syndrome is the location of the pain on the sternum. Costochondritis typically affects the third, fourth, and fifth costosternal joints in contrast to Tietze's syndrome, which usually affects the second or third costosternal joint. Pain from costochondritis typically resolves within one year.

Gait abnormality is a deviation from normal walking (gait). Watching a patient walk is the most important part of the neurological examination. Normal gait requires that many systems, including strength, sensation and coordination, function in an integrated fashion. Many common problems in the nervous system and musculoskeletal system will show up in the way a person walks.

Costochondritis, also known as chest wall pain, costosternal syndrome, or costosternal chondrodynia is an acute and often temporary inflammation of the costal cartilage, the structure that connects each rib to the sternum at the costosternal joint. The condition is a common cause of chest pain. Though costochondritis often resolves on its own, it can be a recurring condition that has little or no signs of onset.

Costochondritis symptoms can be similar to the chest pain associated with a heart attack. Chest pain is considered a medical emergency until life-threatening cardiac issues can be ruled out. Severe cases of costal cartilage inflammation that also involve painful swelling are sometimes referred to as Tietze's syndrome, a term sometimes used interchangeably with costochondritis. However, some physicians view costochondritis and Tietze's syndrome as separate disease states due to the absence of costal cartilage swelling in costochondritis.

Treatment options are quite limited and usually involve a combination of rest, analgesics, or anti-inflammatory medications. Cases with persistent discomfort may be managed with cortisone injections or surgery may be indicated if the condition is severe. Individuals with costochondritis are typically instructed to avoid strenuous physical activity to prevent the onset of an attack.

Computer-induced health problems can be an umbrella term for the various problems a computer user can develop from prolonged and incorrect computer use. A computer user may experience many physical health problems from using computers extensively over a prolonged period of time in an inefficient manner. The computer user may have poor etiquette when using peripherals, for example incorrect posture. Reportedly, excessive use of electronic screen media can have ill effects on mental health related to mood, cognition, and behavior, even to the point of hallucination.

Prior to the 20th century, specialists of pregnancy-related PGP used varying terminologies. It is now referred to as Pregnancy Related Pelvic Girdle Pain that may incorporate the following conditions:

- Diastasis of the Symphysis Pubis(DSP)

- Symphysis pubis dysfunction(SPD)

- Pelvic Joint Syndrome

- Physiological Pelvic Girdle Relaxation

- Symptom Giving Pelvic Girdle Relaxation

- Posterior Pelvic Pain

- Pelvic Arthropathy

- Inferior Pubic Shear/ Superior Pubic Shear /Symphyseal Shear

- Symphysiolysis

- Osteitis pubis (usually postpartum)

- Sacroiliitis

- One-sided Sacroiliac Syndrome /Double Sided Sacroiliac Syndrome

- Hypermobility

""The classification between hormonal and mechanical pelvic girdle instability is no longer used. For treatment and/or prognosis it makes no difference whether the complaints started during pregnancy or after childbirth." Mens (2005)"

The most common injury type suffered by musicians is repetitive strain injury (RSIs). A survey of orchestral performers found that 64–76% had significant RSIs. Other types of musculoskeletal disorders, such as carpal tunnel syndrome and focal dystonia, are also common.

Non-musculoskeletal problems include contact dermatitis, hearing problems such as tinnitus, respiratory disorders or pneumothorax, increased intraocular pressure, gastroesophageal reflux disease, and psychological issues such as performance anxiety.

Musicians may suffer hearing disorders due to noise exposure. They also are at an increased risk of having problems with the stomatognathic system, in particular mouth and teeth, which may in some cases lead to permanent injuries that prevent the musicians from playing.

Woodwind instrumentalists, in rare cases, suffer a condition known as "hypersensitivity pneumonitis", also referred to as "saxophone lung", can be caused by Exophiala infection. It is held that this can occur if instruments are not cleaned properly.

In today’s world using computers is a necessity for the majority of people but not many people actually consider the medical consequences that working with computers can cause, such as damaged eyesight, bad posture, arthritis in fingers and computer stress injuries that can be caused by sitting in one position for a prolonged period of time. The above problems are more commonly associated with old age but due to many factors such as poor component design, proximity of the user to the screen and an excess of consecutive working hours mean that the above problems can feature in both young and old computer users. This is an extremely important issue as computers become more important in every corner of employment the medical effects caused by them will elevate unless sufficient research is performed and time is dedicated into eliminating and reducing these problems as much as possible. It is estimated that today at least 75% of all jobs involve some level of computer use; this means three-quarters of the workforce are being exposed to numerous health problems, the same can be said of students and educators who do not go through any day without access to a computer for academic work. The figure for people working with and using computers recreationally is to increase considerably in the coming years so it is crucially important that these problems are identified and resolved sooner rather than later in an effort to reduce if not eradicate these problems.

Neuromuscular disease is a very broad term that encompasses many diseases and ailments that impair the functioning of the muscles, either directly, being pathologies of the voluntary muscle, or indirectly, being pathologies of nerves or neuromuscular junctions.

Neuromuscular diseases are those that affect the muscles and/or their direct nervous system control, problems with central nervous control can cause either spasticity or some degree of paralysis (from both lower and upper motor neuron disorders), depending on the location and the nature of the problem. Some examples of central disorders include cerebrovascular accident, Parkinson's disease, multiple sclerosis, Huntington's disease and Creutzfeldt–Jakob disease. Spinal muscular atrophies are disorders of lower motor neuron while amyotrophic lateral sclerosis is a mixed upper and lower motor neuron condition.

The exact etiology of tendinopathy has not been fully elucidated and different stresses may induce varying responses in different tendons. There are multifactorial theories that could include: tensile overload, tenocyte related collagen synthesis disruption, load-induced ischemia, neural sprouting, thermal damage, and adaptive compressive responses. The intratendinous sliding motion of fascicles and shear force at interfaces of fascicles could be an important mechanical factor for the development of tendinopathy and predispose tendons to rupture. Obesity, or more specifically, adiposity or fatness, has also been linked to an increasing incidence of tendinopathy.

The most commonly accepted cause for this condition however is seen to be an overuse syndrome in combination with intrinsic and extrinsic factors leading to what may be seen as a progressive interference or the failing of the innate healing response. Tendinopathy involves cellular apoptosis, matrix disorganization and neovascularization.

Tendinopathy can be induced in animal models by a surgical injury to the tendon. In both sheep shoulder (infraspinatus) and horse forelimb (superficial digitor flexor) tendons, a mid-tendon transection caused pathology in the entire tendon after four and six weeks respectively.

Quinolone antibiotics are associated with increased risk of tendinitis and tendon rupture. A 2013 review found the incidence of tendon injury among those taking fluoroquinolones to be between 0.08 and 0.2%. Fluoroquinolones most frequently affect large load-bearing tendons in the lower limb, especially the Achilles tendon which ruptures in approximately 30 to 40% of cases.

Video game-related health problems can induce repetitive strain injuries, skin disorders or other health issues. Other problems include video game-provoked seizures in patients with epilepsy. In rare and extreme cases, deaths have resulted from excessive video game playing (see Deaths due to video game addiction).

After a period of prolonged stability individuals who had been infected and recovered from polio begin to experience new signs and symptoms, characterised by muscular atrophy (decreased muscle mass), weakness, pain and fatigue in limbs that were originally affected or in limbs that didn't seem to have been affected at the time of the initial polio illness. PPS is a very slowly progressing condition marked by periods of stability followed by new declines in the ability to carry out usual daily activities. Most patients become aware of their decreased capacity to carry out daily routines due to significant changes in mobility, decreasing upper limb function and lung capability. Fatigue is often the most disabling symptom; even slight exertion often produces disabling fatigue and can also intensify other symptoms. Problems breathing or swallowing, sleep-related breathing disorders, such as sleep apnea and decreased tolerance for cold temperatures are other notable symptoms.

Increased activity during intervening healthy years between the original infection and onset of PPS can amplify the symptoms. Thus, contracting poliomyelitis at a young age can result in particularly disabling PPS symptoms.