What is a musculoskeletal disorder?
Work-related musculoskeletal disorders (WMSDs) encompass injuries or alterations to joints and other tissues of the musculoskeletal system. They can affect the back, neck, shoulders, arms, hands, and lower limbs. Their manifestations range from pain, fatigue, or numbness to loss of strength, limited mobility, and conditions requiring treatment or sick leave. The course of the disorder depends on the injury, the exposure, and individual characteristics.
Work can be the primary cause, a contributing factor, or an aggravating element. Therefore, not all pain should be automatically attributed to occupation, nor should it be dismissed simply because a pre-existing condition exists. Preventive assessment studies actual exposure, and health surveillance provides individual and collective information, respecting confidentiality.
Differences between musculoskeletal disorders, symptoms, and occupational diseases
A symptom is a manifestation, such as pain, tingling, or stiffness; it may indicate a problem, but it does not, on its own, constitute a diagnosis. A musculoskeletal disorder (MSD) is a clinically identified musculoskeletal condition or one considered in a health assessment. An occupational disease is a legal classification subject, in Spain, to the requirements of the General Social Security Law and the provisions of Royal Decree 1299/2006.
It’s also important to distinguish between prevention and treatment. Physiotherapy or medical attention may be necessary, but they don’t replace correcting the underlying task. If inappropriate exposure persists, simply addressing the individual’s needs shifts the problem and can lead to recurrence. The priority for prevention is to eliminate or reduce the root causes.
Common risk factors
Key biomechanical factors include manual handling of loads , awkward or sustained postures, repetitive movements , force application, and vibrations. Duration, frequency, rhythm, breaks, and recovery time also play a role. Environmental conditions, workspace, tool design, and the ability to adjust the workstation can modify exposure.
Organizational and psychosocial factors also matter: high demands, low autonomy, limited support, or time pressure can increase stress and hinder recovery. Age, experience, abilities, and health status should be considered without using personal characteristics to mask poor job design. A single job may combine several factors; evaluating them separately may underestimate the cumulative risk.
How to identify and evaluate
The evaluation begins by observing the actual work, not just the written procedure. Tasks, cycles, weights, forces, postures, distances, rhythms, times, and the exposed population are described. Reported discomfort, injuries, rotations, and production changes are also reviewed. The participation of those performing the task helps to identify variability, informal adjustments, and critical moments.
The INSST (National Institute for Safety and Health at Work) recommends selecting the method based on the factor: handling, pushing and pulling, repetitiveness, posture, or movement of people, among others. An initial identification, a rapid assessment, and, if inconclusive, a detailed evaluation can be used. The method must be appropriate to the situation and applied by competent personnel. After implementing measures, the observation is repeated to check if exposure decreases and if new risks appear.
How to prevent it
Prevention follows a hierarchy. First, unnecessary handling or effort is eliminated through redesign, mechanization, or process changes. Then, weights, reaches, forces, and repetitions are reduced; height and layout are improved; aids are incorporated; and work is organized to allow for recovery. Training teaches how to use the designed system, but it does not compensate for a physically unsuitable task.
Breaks and rotations are only effective if they actually reduce exposure; alternating tasks with the same muscle load does not constitute recovery. Assistive devices should be evaluated and maintained. Targeted health monitoring can detect effects early and identify particularly sensitive individuals, and its collective results should inform the assessment without disclosing clinical data.
Practical example
In an order picking area, staff lift boxes from low pallets, twist their torsos, and place them above shoulder height. Frequent repetitions and lower back and shoulder discomfort are observed. The assessment confirms that the combination of height, reach, weight, twisting, and pace requires intervention.
The company raises the pallets, positions the destinations between knee and shoulder height, reduces the unit weight, incorporates assistance for less manageable loads, and reorganizes supply to avoid peak periods. It then trains staff on the new method and verifies its use. Follow-up compares exposure, incidents, and collective discomfort, and reviews the assessment when the box format changes. Simply delivering a talk on “posture hygiene” would have left the root causes untouched.
Regulatory framework in Spain
Law 31/1995 mandates the prevention of risks, their assessment when they cannot be avoided, and the adaptation of work to the individual, particularly with regard to job design, equipment selection, and work methods. Royal Decree 39/1997 regulates risk assessment and planning. For specific exposures, Royal Decree 487/1997 establishes provisions on manual handling of loads with risks, especially to the lower back, and Royal Decree 488/1997 addresses equipment with display screens.
The applicable regulations depend on the task and may include equipment, vibrations, or other conditions. The INSST technical guidelines provide non-binding criteria to facilitate the application of the Royal Decrees; the guide for manual handling of loads was updated in 2024. The legal framework does not establish a single universal method for all musculoskeletal disorders (MSDs): it requires a procedure that provides confidence and allows for the decision of appropriate measures.
