Introduction

Work related musculoskeletal disorders are a group of painful conditions can affect bones, muscles, nerves, tendons and joints. The common WMSD’s seen include carpal tunnel syndrome, thoracic outlet syndrome and tension neck syndrome.

The U.S. Department of Labour defines WMSDs, as injuries or disorders of the muscles, nerves, tendons, joints, cartilage, and spinal discs associated with exposure to risk factors in the workplace.

WMSDs include :-

• sprains,
• strains,
• tears,
• swelling,
• fractures,
• compression,
• misalignment,
• disc herniation
• excessive, repetitive movements that affect the musculoskeletal, connective, or nervous system

This can be due to activities which require :

• lifting
• bending
• climbing
• crawling
• reaching
• twisting
• pushing
• pulling
• poor postural alignment
• psychological stress
• overexertion
• repetition

WMSDs do not include disorders caused by slips, trips, falls, motor vehicle accidents, or other traumatic injuries.

Most jobs requires the use of hands ,and arms. As a result majority of the WMSD incidences affect the neck , shoulder, arms, elbows and wrists. Certain occupations require prolonged walking or standing leading to WMSD of the hips , thighs, ankles, knees and feet. In addition repetitive activities can also lead to back disorders.

Risk factors for WMSD

1. Physical and Biomechanical Risk Factors
   – Repetitive movement when working
   – Forceful movements
   – Repetitive forceful tasks
   – Fixed position while working
   – Awkward and unnatural body positions
   – Using vibrating equipment
   – Extreme temperature
   – High altitude
2. Psychosocial Risk Factors
   – Increased stress or demands
   – Poor job satisfaction
   – Unstable job security
   – Low decision control
   – Low salary and poor benefits
   – Bad relationships with supervisors
   – Poor support at workplace
3. Individual Predisposing Risk Factors
   – Genetic make up
   – Co-morbid medical conditions
   – Sedentary lifestyle
   – Physical and psychosocial coping behaviors
   – Personality issues
   – Obesity
   – Ageing
   – Female gender
   – Life goals and family responsibilities

Figure 1 : Physical and Biomechanical Risk Factors

 

How do WMSD’s Occur

Muscle Injury

When we use our muscles , its uses energy from food and it will produce certain toxic-products. One of the common products is lactic acid. A muscle that is contracted for a long time will lead to less blood flow to the muscle. Therefore it takes time for the lactic acid to clear. This leads to additional time for the muscle to remove the acid from the body causing pain and irritation to the muscle.

Figure 2 : Muscle size and blood flow

 

Tendon Injury
Tendons are fibres that join muscles to bones. Diseases of the tendon can happen when we use our arms and legs repeatedly and also working in awkward position. Tendons are usually present in the hands, wrists, shoulder , elbow and forearm. In the hand , the tendon moves in sliding manner surrounded by the covering or sheaths.

Figure 3 – Tendons around fingers and their sheaths

 

Figure 4 – Tendon and muscle

Due to repetitive work and awkward position , the tendon can get swollen which then makes movement difficult inside the sheath leading to pain and swelling.

Figure 5 : swollen tendon

 

Nerve Injury

Figure 6 : Carpal tunnel sydrome

Nerves carry instructions from brain for muscles to work. They carry detailed information of touch, sensation, temperature , vibration and pain. Many nerves are surrounded bu muscles, tendons , bones and ligaments. When one has to perform repetitive jobs at awkward positions, the tissues around the nerves become swollen. Swelling around the nerves will press and squeeze the nervous tissue.

Figure 7 : Thickening of tendon sheath pressing upon nerve

Features of WMSD

The most common symptom is pain. Many people will also have redness, stiffness, tightness and swelling in the particular area. Employees also complain of change in skin color, less sweating in palms and pin and needle sensation.

Stages of WMSD

i. Fatigue , feeling uncomfortable, localised pain which is worse while working and better after rest

ii. Continuous , intense pain with numbness and burning sensation. It is worse with work and daily activities . It decreases productivity.

Iii. Continuous , intense pain which is partially relieved by rest. It is linked to reduced muscle strength, swelling, numbness. He or she is less productive or unable to work

iv. Severe continuous pain with suffering . He or she is unable to do any work at all

How to recognize WMSD

1. History of pain

Characterize the symptoms and history
Ꝋ Onset (date; circumstance; abrupt vs. gradual, etc.)
Ꝋ How long do you have pain. How frequent do you have pain
Ꝋ Quality (pain; tingling; numbness; swelling; tenderness, etc.)
Ꝋ Severity of pain (mild; moderate; severe)
Ꝋ Where is the location of the pain
Ꝋ Is the pain spreading elsewhere
Ꝋ Relieving and aggravating factors of pain ( during work and when not working)
Ꝋ Prior treatment

2. Other important considerations

Demographics (e.g., age; gender; hand dominance)
Previous history of any injury of illness of the affected area )
Recreational activities, hobbies, household activities
Occupational history with emphasis on the:
i. job the employee was performing when the symptoms first seen
ii. prior job if the employee recently changed jobs,
iii. amount of time spent on that job,
iv. whether the employee was working elsewhere or part-time jobs

3. Job characterization
4. Medical examination
5. Assessment and diagnosis

Treatment

Restricting Movement
One of the main approaches to treat WMSD is to stop activities leading to injury. This needs work restrictions. In certain instances, the employee may need to be transferred to a different job or task. Splint is also useful to reduce movements or immobilze an injured area.

Splints are used mainly for two reasons
a. To support a joint mechanically where excessive load is expected
b. To decrease movement of the injured joint

Applying heat or cold compression
Heat or cold compression can relief pain and fasten the healing process
Cold decreases pain and swelling and is beneficial for injuries and inflammation i.e. parts that are swollen, red and warm. Using ice is not common for muscle pain as cold conditions leads to increase in muscle contraction, therefore delaying recovery.

Warm compression is useful to alleviate muscle pain. Heat accelerates the blood flow which in turn decrease the amount of lactic acid accumulated in muscle. Gradually as the lactic acid amount diminishes, muscle pain also improves.

Exercise

Stretching is a common exercise as it enhances blood circulation and decreases muscle tension. Therefore , people who commonly suffer from WMSD should opt for exercise on a regular basis. This approach should be conducted under the guidance of trained staff (e.g., ergonomist, physical and occupational therapists).

Medication
Painkillers are vital to reduce the symptoms via their analgesic and anti-inflammatory effects.. Despite this, painkillers are only used on a need-to-use basis and not routinely. Certain conditions refractory to conventional treatment, local injection of a corticosteroid might be indicated. Adding an anesthetic agent can provide valuable diagnostic information.

Surgery

An efficient ergonomics and medical management program, hardly warrants surgical intervention . Surgery should be used when medical treatment does not offer improvement.. While certain indications for urgent surgical interventions may still be present (e.g., ulnar artery thrombosis), it is reserved for severe cases (e.g., severe pain leading to functional limitations) not responding to an adequate trial of conservative therapy.

Prevention

1.Sufficient training for workers, supervisors and managers in prevention principles including health promotion e.g. proper body mechanics, engineering controls, and early anticipation of the features of WMSDs

2. Requirements for employers to institute engineering controls whenever feasible through proactive changes in work and tool design to reduce or eliminate potentially hazardous conditions;

3. Changing work practices and management policies to decrease hazardous situations.

4. Suitable medical management to diagnose and manage WMSDs

5. Appropriate health,medical and hazard surveillance

 

References :

https://www.ccohs.ca/oshanswers/diseases/rmirsi.html
https://www.cdc.gov/workplacehealthpromotion/health-strategies/musculoskeletal-disorders/evaluation-measures/index.html
KARWOWSKI, W. (Ed)., 2001, International Encyclopedia of Ergonomics and Human Factors. (London: Taylor & Francis)