Finding the Risk Factors for Work-Related Musculoskeletal Disorders

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Step 1 of NIOSH's guide to building a workplace ergonomics program.

Work-related musculoskeletal disorders (WMSDs) and injuries can happen to anyone. A problem may be limited to one job or task, or spread across several departments. The first step is to find where the risk lies: who is affected, which conditions raise the risk, and which jobs carry it.

Start with the records

Records of complaints and injuries are often enough to show how big a WMSD problem is. OSHA logs and company medical records, which most employers already have, can be used to work out incidence (new cases) and prevalence (new and existing cases), which feed into Step 3 of the program. Places to look:

Record	What to look for
OSHA Form 300 logs and workers' compensation claims	specific diagnoses such as carpal tunnel syndrome or tendinitis, and nonspecific ones such as hand, wrist or back pain
Worker complaints	undue stress, localized muscle fatigue, discomfort, pain that does not go away with rest
Clinic visits	aches and pains linked to particular work assignments
Job task evaluations and job safety or hazard analyses	repetitive and forceful exertions, vibrating equipment
Company policies and directives	changes such as faster line speeds made to raise output
Trade publications	evidence of WMSDs in the field

An organization that finds a possible WMSD problem can ask NIOSH for a Health Hazard Evaluation (HHE), and can search past HHE reports under terms such as "ergonomics" or "musculoskeletal disorders."

Physical risk factors

Physical stress comes from the force, repetition and postures a task demands. NIOSH's Practical Demonstrations of Ergonomic Principles (2011) distinguishes three kinds of posture:

neutral, with muscles and joints resting and relaxed;
awkward, which makes muscles, tendons, nerves and bones work harder and can lead to WMSDs;
static, holding one position for a long time, which adds muscle fatigue and can disrupt blood flow, even in a neutral posture.

Examples of physical risk factors include awkward postures, overhead work, twisting while carrying loads, contact stress, poor shoulder and wrist posture, lifting bulky loads, and whole-body vibration. Often more than one is present at once, such as contact stress and excessive force while pushing a cart.

Psychosocial risk factors

Psychosocial stress also affects workers' musculoskeletal health. It comes from:

work organization: a tiring workload, repetitiveness, lack of control over the job, extreme mental demands, low job satisfaction;
life outside work: parenting, personal health, money worries;
the individual: genetics, education, culture, personality.

Which jobs carry risk

A single task can carry several risk factors, and the level of risk depends on their intensity, frequency and duration. The Bureau of Labor Statistics' Occupational Requirements Survey rates physical demands at five levels, sedentary, light, medium, heavy and very heavy, and job requirements become risk factors when intensity, frequency or duration are high.

NIOSH Worker Health Charts, based on the 2015 Occupational Health Supplement to the National Health Interview Survey, give unadjusted estimates by occupation:

Among U.S. adults	Estimated number	Prevalence
Frequent lifting, pushing, pulling or bending at work	60,471,000 of 145,777,000	41.48%
Frequent standing or walking	97,314,000 of 145,818,000	66.74%
Low back pain attributed to work	8,274,000 of 147,742,000	5.68%
Current carpal tunnel syndrome attributed to work	2,445,000 of 145,699,000	1.68%

Disorders and their risk factors

A 1997 NIOSH review of the literature linked WMSDs in five body regions to risk factors with strong or some evidence at the time:

Disorder	Risk factors
Neck	repetition with awkward neck posture; forceful arm and hand work; static awkward posture (tension-neck syndrome)
Shoulder (tendinitis)	repetition with awkward shoulder posture; static shoulder load; overhead work
Elbow (epicondylitis)	forceful work; force combined with repetition or posture
Carpal tunnel syndrome	force with repetition, force with posture, or all three
Hand/wrist tendinitis	high repetition with forceful hand or wrist exertion
Hand-arm vibration syndrome	intensity and duration of vibrating tools, for example 5–36 m/s²
Low back	heavy physical work; lifting and forceful movements; bending and twisting; whole-body vibration; static posture

Screen with checklists

Checklists compare the features of a job against a list of risk factors.

Walk through the workplace and observe. Watch several workers doing the same task at the same time to see the different postures and techniques they choose.
Interview workers and supervisors, gathering information only from those familiar with the job, task or process.
Adapt the checklists to each kind of work; no single checklist fits every situation. Results can later be combined to gauge the extent of the problem.

NIOSH provides checklists for workstations, task analysis, hand tools, materials handling and computer workstations, a hazard identification checklist, and a protocol for video recording jobs. Checklists can reveal separate problems with a shared cause, and help brainstorm first solutions; sometimes the fix is simple and a full intervention is not needed.

Going further. Follow up with measurements: time-motion patterns of tasks and job cycles, workstation layouts, tool handle sizes, weights and vibration, whole-body vibration, heat and cold, and workers' physiological and biomechanical responses.