Overview of the musculoskeletal field

Musculoskeletal disorders (MSK) are a common term complaints, disorders, discomfort, or impaired function in (1):

• bones
• joints
• muscles
• tendons
• nerves

The concept encompasses a very wide range – from:

• mild, transient ailments (e.g., acute neck strain, temporary muscle tension)
• via chronic, long-lasting pain and functional disorders (e.g., long-term back pain,
• tendinopathies, osteoarthritis)
• to severe pain conditions that make even simple tasks impossible (e.g., pronounced radiculopathy, advanced osteoarthritis, inflammatory arthritis) (1,2)

MS disorders are not one disease, but a whole field – with great variation in causes, course, prognosis, and treatment needs. The common denominator is that they affect the musculoskeletal system and often cause pain, stiffness, loss of function (1), and reduced participation in work and society.

2.1 One of the biggest health problems in Norway

musculoskeletal complaints are today one of the biggest health problems in Norway. They:

• are among the most common reasons for contacting a general practitioner (3)
• are the most common cause of sick leave (4)
• are one of the most common causes of disability (5)
• accounts for a large part of the non-fatal health loss (DALYs), DALY = Disability‑Adjusted Life Year. One DALY corresponds to one lost year of full health – either because one dies prematurely, or because one lives with disease/ailments that reduce the health level. DALY thus combines years lost due to premature death and years lived with reduced health into a single measure of health loss. This makes it possible to compare the burden of completely different diseases on a common scale and shows how significant the consequences of non-fatal conditions actually are for the population's health. (6)
• entails significant societal costs (7) (sick pay, disability pension, treatment, rehabilitation, aids)

2.2 Affects labor participation and dropout

MSK disorders affect both (4.8):

• participation in working life – ability to stay in work, work full-time, handle strain
• dropout from working life – sick leave, graded sick note, disability

Figures from work environment examinations show that:

• 68% of all employed in Norway report that they have been troubled by pain in the neck, shoulders, back, arms, or legs during the past month (9)
• 3 out of 5 reports that the complaints are wholly or partly due to the current job (9)

This means that musculoskeletal complaints are not a marginal phenomenon, but a normal part of working life – and a main cause of reduced work ability.

3.1 Socioeconomic gradient

musculoskeletal complaints are more common among people with lower socioeconomic status than in the population as a whole. Studies have shown that:

• People with low education have approximately three times higher risk risk of becoming disabled due to back disorder compared to people with higher education (10).

This reflects several factors (10,11):

• heavier physical work
• more monotonous and strenuous work tasks heavier physical work
• less control over the work situation
• less flexibility and accommodation
• higher exposure to risk factors (lifting, vibration, working on knees, working above shoulder height)
• often also greater burden from other health and living condition problems

MSK epidemiology is therefore also social medicine: who develops disorders, and who drops out of work, is closely related to education, income, and working conditions.

3.2 Geographical differences

There is a large regional differences use of health services for MSK conditions (12). We know that:

• some regions have higher use of imaging, surgery, and specialist healthcare services
• others have higher use of conservative treatment (physiotherapy, manual therapy, rehabilitation)

The causes are not fully understood, but may include (12):

• varying access to services
• different practices among general practitioners and specialists
• different population composition (age, occupations, socioeconomics)
• different culture for sick leave, treatment, and “normalization” of pain

For you as a doctor, this means that patient pathways are not only governed by disease, but also where the patient lives and which services are available.

4.1 Work environment as a cause and amplifier

Factors in the work environment can (9,13):

• be a direct cause to MSK complaints
• contribute to trigger complaints in vulnerable individuals
• worsen already existing complaints
• make it difficult to return to work after illness

Traditionally, the focus has been on mechanical loads:

• unfavorable working positions
• repetitive movements
• heavy lifting
• work on knees or in a squat
• work above shoulder height
• vibration (whole-body or hand-arm) (13)

But we now know that organizational and psychosocial factors also has great importance (14):

• time pressure
• high quantitative demands
• role conflicts
• low job control
• little support from leaders and colleagues
• unpredictability
• low job satisfaction

These factors affect both:

• the risk of developing MSK complaints
• the risk that complaints become long-term
• the risk of sick leave and disability

4.2 Protective factors in the work environment

There are also protective factors that reduce the risk of disease and promote health (14):

• interesting work tasks
• good relationships with colleagues and superiors
• fair salary
• high degree of autonomy
• clearly defined work tasks
• professional development opportunities

These factors can:

• increase job satisfaction
• reduce perceived stress
• increase sense of mastery
• make it easier to stay at work despite ailments

Low job satisfaction, on the other hand, can contribute to both mental and somatic illness – including MSK complaints (14).

5.1 Neck and shoulder pain

Neck and shoulder pain are among the most common MSK complaints in the working population (9).

Causes and risk factors

The causes are often complex:

Mechanical factors:

• static and repetitive work tasks
• monotonous arm and hand movements
• work with the arms raised above shoulder height
• work with the head bent forward

Psychosocial factors:

• high degree of role conflicts
• high job demands
• low level of supportive leadership
• low job control

Research from STAMI shows that approximately one in four cases of moderate to severe neck and shoulder pain in the Norwegian workforce can be attributed to mechanical and psychosocial work environment factors (9).

Prevalence

• 33 % of employees have work-related pain in the neck and shoulders – about 870,000 people
• In total, 55 % have pain in the neck or shoulders during a month (9)

This shows that neck and shoulder pain is almost the norm in working life.

5.2 Arm pain

Arm pain (forearm, wrist, hands) is also common and often work-related.

Mechanical factors (13)

• repetitive hand or arm movements over a long period
• little variation in work tasks
• PC work with keyboard and mouse > 20 hours per week
• manual work with repetition + use of force
• use of vibrating hand tools (impact tools, drills, grinders)

This can cause:

• tendinopathies
• muscle complaints
• nerve compression syndrome (e.g. carpal tunnel syndrome)
• hand-arm vibration syndrome (HAVS)

Prevalence

• 29 % have pain in the arms overall.
• 18 % have work-related arm pain – approx. 480,000 people (9).

5.3 Back pain

Back pain, especially in the lower back, is one of the most common causes of (3,4,5):

• contact with a general practitioner
• sick leave
• disability

Causes and risk factors

• Mechanical factors:
  • heavy and awkward lifting
  • work in a squatting or kneeling position
  • work in a standing position most of the day
  • whole-body vibration (e.g., driving large vehicles)
  • combination of several exposures (lifting + standing work)
• Psychosocial factors:
  • high job demands
  • low control
  • low support
  • role conflicts

Norwegian data show that:

• approx. 90 % of those with chronic low back pain also have MSK complaints in other parts of the body – that is, a pattern of multiregional pain (15).
• approx. 42 % of cases with moderate to severe low back pain can be related to exposure at work/work environment (9).

Prevalence

• 49 % have back pain in total.
• 23 % have work-related back pain – approx. 610,000 people (9).
• 1.5% of the employed are treated annually for back disorders – approx. 17,100 people.

5.4 Pain in the legs (hip, knee, foot)

Pain in the hips, knees, and feet is often associated with (13):

• heavy physical work
• prolonged standing work
• work in a squatting or kneeling position
• repeated heavy lifting

This can lead to:

• strain injuries
• tendinopathies
• osteoarthritis (especially in hip and knee) (16)

Osteoarthritis and work

• heavy physical work and knee-/squatting work increase the risk of hip and knee osteoarthritis
• combination of knee/squatting work + heavy lifting further increases the risk
• prolonged standing work is also associated with increased risk of osteoarthritis in several meta-analyses

Prevalence

• 42 % have pain in the legs overall.
• 17 % have work-related pain in the legs – approx. 450,000 people.
• 1.1% of the employed are treated annually for osteoarthritis in hip/knee – approx. 12,500 people (9).

In a large Norwegian cohort study (approx. 198,000 patients, 2008–2020), the distribution of pain location in MSK disorders (17) was:

Pain location	Proportion (%)
Back	25
Shoulder/arm	16
Hip/knee	13
Neck	8
Fracture, joint and ligament injury	8
Widespread pain	4
Osteoarthritis	2

The patients were:

• 50% with education after high school
• 80% employed
• 30% with immigrant background

This shows that MSK disorders:

• affect a wide range of the population
• are often located in the back, shoulder/arm, and hip/knee
• often occur in people who are employed

MSK patients move through several parts of the health service (18):

• General practitioner: approx. 32 %
• specialist healthcare services: approx. 16 %
• Physiotherapist or chiropractor: approx. 12 %

In the general population:

• approx. 18 % of men and 27 % of women have MSK disorders lasting > 6 months

Another study showed that:

• approx. 29 % of the population have annual contact with a general practitioner for MSK symptoms (18)
• about 6% have contact with hospital/specialist
• about 12% have contact with chiropractor/physiotherapist
• about 25% of those who have contact with health services for MSK symptoms have long-term complaints (> 3 months), and of these, most are women > 70 years

This emphasizes:

• the general practitioner as the main entry point
• physiotherapists and chiropractors as important players in conservative treatment
• specialist healthcare services as a smaller but costly part of the course

The proportion of residents over 70 years is steadily increasing. There is a strong correlation between:

• age
• prevalence of MSK disorders
• need for health services

When the proportion of elderly increases, the following will occur:

• the number of people with osteoarthritis, osteoporosis, back pain, and other MSK disorders will increase (19)
• the need for treatment, rehabilitation, and facilitation will increase
• pressed on general practitioners, physiotherapists, and specialist healthcare services to increase

For health service planning, the proportion > 70 years is therefore a critical demographic variable.

Data from KUHR (2010–2016) shows (20):

• The proportion of users of general practitioners for MSK complaints is stable for the age group 0–44 years
• It is increasing for the age group 45–74 years
• Women are more frequent users than men in both age groups

This reflects:

• increasing prevalence of MSK disorders with age
• gender differences in both prevalence, pain perception and health behavior

ICPC-2 (International Classification of Primary Care) is the diagnostic system used in general practice in Norway. To understand the epidemiology in the MSK field, one must understand how general practitioners actually code patients' complaints.

ICPC-2 is structured as follows:

• Blue codes (1–29): symptoms and complaints
• Pink codes (70–99): disease diagnoses (21)

This distinction is crucial, because the MSK field in primary healthcare is dominated by symptom diagnoses, not disease diagnoses. This reflects reality: most MSK complaints are nonspecific, multifactorial and without one clear pathoanatomical cause.

10.1 The L Chapter – the musculoskeletal system

The L chapter in ICPC-2 covers the entire MSK field. It includes:

• neck
• back
• shoulder
• arm
• elbow
• wrist
• hip
• knee
• ankle
• foot
• general muscle complaints
• widespread pain
• osteoarthritis
• bursitis/tendinitis
• injuries
• fractures
• deformities
• inflammatory conditions

10.2 Symptom diagnoses

Examples:

• L01: Neck complaints
• L02: Back complaints
• L08: Shoulder complaints
• L15: Knee complaints
• L17: Foot problems
• L18: Widespread muscle pain/fibromyalgia
• L19: Muscle complaints IKA
• L20: Joint disorders IKA
• L28: Reduced functional ability due to MSK problems

These codes are used when

• the cause is unclear
• the condition is nonspecific
• that there is no structural disease
• there is no indication for a specific diagnosis

This is very common in the MSK field.

10.3 Disease Diagnoses

Examples:

• L83: Neck Syndrome
• L84: Back Syndrome without Radiation
• L86: Sciatica
• L87: Bursitis/Tendinitis/Synovitis
• L88: Rheumatoid Arthritis
• L89: Hip Joint Osteoarthritis
• L90: Knee Joint Osteoarthritis
• L92: Shoulder Syndrome
• L93: Tennis Elbow
• L95: Osteoporosis
• L96: Acute internal knee injury

These codes are used when:

• there is a clear medical diagnosis
• there are objective findings
• the condition is defined by pathology

10.4 Gender differences in symptom diagnoses

Percentage of men:

• Neck complaints (L01): 35%
• Back complaints (L02): 45%
• Shoulder complaints (L08): 48%
• Knee problems (L15): 49 %
• Foot problems (L17): 43 %
• Muscle pain/fibromyalgia (L18): 21 %

This shows that women dominate in most symptom diagnoses, especially widespread pain and fibromyalgia.

10.5 Gender differences in disease diagnoses

Percentage of men:

• Neck syndrome (L83): 40 %
• Back syndrome without radiation (L84): 50 %
• Sciatica (L86): 52 %
• Bursitis/tendinitis (L87): 41 %
• Rheumatoid arthritis (L88): 31 %
• Knee osteoarthritis (L90): 36 %
• Shoulder syndrome (L92): 43 %
• Unspecified MSK disease (L99): 37 %

Here, the gender differences are smaller, but women are still overrepresented in most diagnoses.

11.1 Symptom diagnoses dominate the MSK field

72% of the population have at least one general practitioner consultation during the year, 48.7% of all diagnoses made by general practitioners are symptom diagnoses (SSB 2024). In the MSK field, the proportion is even higher. There is an overlap between mental disorders and musculoskeletal complaints—a complex disorder—but there is no data on this in SSB. However, we can estimate how many receive both diagnoses. About 11% of patients who use the GP during the year receive both at least one psychiatric (P diagnosis) and at least one musculoskeletal diagnosis (L diagnosis). There is an overlap between mental disorders and musculoskeletal complaints—when both diagnoses are given, we call it a complex disorder. About one in ten adult patients in general practice can therefore be expected to have both musculoskeletal disorders and mental disorders. This is a conservative estimate because mental disorders are often underdiagnosed and undercoded, and comorbidity between pain and mental disorders is systematically higher than what you get by assuming independence between the disease conditions.

This means:

• MSK complaints are often nonspecific and often part of a complex disorder
• MRI findings and structural diagnoses explain only a small part
• clinical reasoning is more important than imaging diagnostics
• treatment must focus on function, coping, and activity
• patient communication is crucial

11.2 The diagnosis often says little about the cause

Example:

“L02 Back pain” says nothing about:

• muscular vs. sclerotomal pain
• radiculopathy vs. nonspecific pain
• psychosocial factors
• work situation
• prognosis

Therefore, the diagnosis must always be supplemented with (22):

• pain history
• functional assessment
• work situation
• psychosocial factors
• expectations and coping

11.3 The diagnosis guides the patient's understanding

A diagnosis such as:

• “wear”
• “degeneration”
• “worn-out back”

…can create:

• fear
• avoidance
• passivity
• reduced function
• increased risk of chronification

Therefore is choice of words a part of the treatment.

Figures from 2022 show that MSK disorders constitute:

• 13.7% of all general practitioner consultations (3)
• 1.24 million consultations for local pain/inflammation
• 568,000 consultations for back problems
• 268,000 consultations for joint and rheumatic diseases
• 210,000 consultations for general muscle complaints

This means:

• The MSK field is one of the largest diagnostic groups in primary health care
• you will meet MSK patients every day
• you must be confident in handling non-specific complaints
• you must be able to assess when further investigation is needed

13.1 General practitioner (32%)

The general practitioner is the main gateway for:

• acute complaints
• long-term pain
• sick leave
• coordination of treatment
• assessment of the need for physiotherapy, imaging, or specialist

13.2 Physiotherapist/chiropractor (12%)

These are central for (3):

• functional assessment
• exercise
• rehabilitation
• manual treatment
• mastery

13.3 specialist healthcare services (16%)

Here treated:

• severe injuries
• surgical conditions
• inflammatory diseases
• advanced osteoarthritis
• complex pain conditions

The proportion of residents over 70 years is steadily increasing. This means:

• more with osteoarthritis
• more people with osteoporosis
• more people with back pain
• more people needing rehabilitation
• increased pressure on the general practitioner scheme
• increased need for physiotherapy and aids

Aging is one of the strongest drivers of MSK disease (19).

1. MSK disorders are among the most common health problems in Norway.
2. They affect work ability, quality of life, and the economy.
3. Most MSK diagnoses in primary healthcare are symptom diagnoses.
4. Gender differences are clear – women are more affected.
5. Work environment plays a large role – both mechanical and psychosocial.
6. Back, neck, shoulders, arms, and legs are the most common pain locations.
7. Aging will significantly increase the prevalence of MSK disorders.
8. Good MSK treatment requires:
   • a good medical history
   • understanding of pain physiology
   • assessment of work and psychosocial factors
   • reassurance and self-management
   • function-oriented treatment

1. Norwegian Institute of Public Health (FHI). Musculoskeletal disorders – facts and prevalence. Oslo: FHI; 2023.
2. Woolf AD, Pfleger B. Burden of major musculoskeletal conditions. Bull World Health Organ. 2003;81(9):646–56.
3. The Norwegian Directorate of Health. Activity data for the GP scheme 2022–2024. Oslo: The Norwegian Directorate of Health; 2024.
4. NAV. Sickness absence statistics – diagnosis distribution. Oslo: NAV; 2023.
5. NAV. Disability statistics – causes of disability. Oslo: NAV; 2023.
6. Global Burden of Disease Study (GBD). Global, regional, and national burden of musculoskeletal disorders. Lancet. 2020.
7. The Norwegian Directorate of Health. Health-related social costs 2019–2021. Oslo: The Norwegian Directorate of Health; 2024.
8. OECD. Sickness, Disability and Work: Breaking the Barriers. Paris: OECD Publishing; 2022.
9. STAMI – The National Institute of Occupational Health. Fact Book on Work Environment and Health 2023. Oslo: STAMI; 2023.
10. Brage S, Ihlebæk C, Natvig B. Musculoskeletal disorders as causes of sick leave and disability pension. Tidsskr Nor Legeforen. 2010;130:2369–73.
11. Dahl E, Bergsli H, van der Wel KA. Social inequality in health. Oslo: Oslo and Akershus University College; 2014.
12. The Norwegian Directorate of Health. Variation in the use of health services – geographical differences. Oslo: Norwegian Directorate of Health; 2022.
13. STAMI. Work-related musculoskeletal disorders – mechanical exposures. Oslo: STAMI; 2022.
14. STAMI. Psychosocial work factors and health. Oslo: STAMI; 2021.
15. Natvig B, Ihlebæk C, Bruusgaard D. Musculoskeletal complaints in a population: multiregional pain. Eur J Pain. 2001;5(4):421–6.
16. Cooper C, Arden N. Occupational activity and osteoarthritis. Best Pract Res Clin Rheumatol. 2000;14(1):47–62.
17. National registry study (2008–2020). MSK disorders in the Norwegian primary health service. Unpublished, but discussed in the Directorate of Health's analyses 2022.
18. The Norwegian Directorate of Health. Use of health services for musculoskeletal disorders. Oslo: Norwegian Directorate of Health; 2021.
19. Statistics Norway (SSB). Population projections – ageing and health service needs. Oslo: Statistics Norway; 2023.
20. the KUHR register. Consultation data for general practitioners 2010–2016. Oslo: Norwegian Directorate of Health; 2017.
21. ICPC-2. International Classification of Primary Care, 2nd edition. WONCA; 2015.
22. The Health Library. National professional guidelines for musculoskeletal disorders. Oslo: Norwegian Directorate of Health; 2023.