Due to the fact that musculoskeletal diseases do not occur randomly but may be related to specific stressors and loads in the maritime environment, the exposure history may provide important clues to the diagnosis. Theoretical considerations with regard to the body structures impacted by a given physical exposure may naturally lead to a particularly detailed study of these body structures at the physical examination. In a corresponding manner, the description of a traumatic event is likely to give rise to hypotheses about the nature and location of the lesion, which may then be studied closely at the physical examination. Such analysis is an important foundation for the diagnostic assessment and consequently for good management of the condition.

Another aspect to be emphasized is that the locomotor system must be perceived as a coherent structure. A lesion in one place can – and usually will – lead to an altered function and to pathology elsewhere. Symptoms can spread out or even be dominating at an entire different location than initially with phenomena such as referred pain, radicular pain, or spread of pain in the course of a particular nerve. Contralateral spread is also a well-known phenomenon, which can be explained from pathophysiological reasoning. These examples show that the disease is not necessarily located where symptoms dominate. The recognition of this fact requires us to conduct a broader assessment of the patient and a physical examination that extends beyond the symptomatic area(s).

The challenges that physicians meet when they diagnose musculoskeletal conditions, whether or not of a work-related character, may result in a tendency to limit the content and thoroughness of the physical examination of patients and to rather rely on paraclinical studies such as imaging or electrophysiological studies of nerves. This is unfortunate and may result in patients being misinterpreted and misdiagnosed and subsequently given wrong or no advice and treatment. It must be stressed that plain radiographs are often of little assistance and that the validity of, e.g. MR-imaging and the study of nerve conduction velocity and electromyography is also limited. These examinations may turn out completely normal even with serious conditions and may also be abnormal in non-symptomatic seafarers.

During the diagnostic process, the clinician aims to identify the tissue with the lesion (e.g., muscle, bone, tendon, insertion, ligament, nerve), more specifically, what structure (e.g. which muscle or tendon), and which pathology (e.g. inflammation, tumour). The history and the physical examination may – provided it is sufficiently thorough – explain the condition in most situations.

Pain is usually the main symptom in musculoskeletal disorders. It is of importance to clarify the nature of pain, whether nociceptive or neuropathic, because the background and treatment differs for these two types of pain. Neuropathic pain may emanate from parts of the nervous system - including nerve roots and peripheral nerves while nociceptive pain is related to other tissues. The pain accompanying carpal tunnel syndrome, and the radicular pain of a herniated disk with root compression are examples of a neuropathic pain. The pain with, e.g. epicondylitis, rotator cuff tendinitis or osteoarthritis is a nociceptive pain. The two types of pain may co-exist.

Neuropathic pain has a tendency to spread to larger and larger areas (also contralaterally). It is often of a burning or neuralgia like nature and responds poorly or not at all to common analgesics. Typically, this pain is exacerbated following use of the involved structures and may persist for a long time subsequently. It is frequently accompanied by sensory phenomena such as paresthesia or allodynia, and by subjective weakness. If the pain is related to a peripheral nerve affliction, there will be tenderness over the involved nerve segment, while the Tinel sign (which indicate ongoing nerve-regeneration) should not be regarded as an obligate phenomenon. This pain may be misinterpreted as nociceptive and due to a disorder of non-nervous structures or – worse – may be regarded as psychogenic because a standard physical examination does not indicate any pathology.

Nociceptive pain usually remains localized and responds to common analgesics. The pain typically worsens with use and improves/disappears at rest. Sensory phenomena such as hypalgesia or allodynia are absent and there are no paretic muscles. There is tenderness localized over structures such as a joint, a tendon or an insertion. The pain is aggravated by compression, by active use or by movement such as passive stretching of a tendon or manipulation of a joint.

The assessment involves information about the dissemination of pain and provocative factors. Combined with a judgment of the character of pain, one can frequently predict findings that are to be expected at the following physical investigation. In case of a neuropathic pain, it is common to find patterns of neurological abnormalities at the physical examination. When the pain is not assessed as neuropathic, one can rather expect signs suggestive of pathology in tendons or insertions ions (local tenderness, pain provocation by passive drag or active stretch, and possibly swelling, heat or redness), bursa and joints (pain provocation on movement, restricted movement), or ligaments (local tenderness).

X-ray, MR-imaging, and ultrasound and isotope scintigraphic examinations and are important tools, but they can never replace a physical examination. For example, "pathological" MR changes suggesting, e.g. a low back disc herniation, are frequent in people who have never had back complaints. Thus, there is limited diagnostic specificity. Similarly, a normal MR study does of course not rule out the presence of disease. This knowledge may be trivial to the doctor but not to patients and laypersons. In order to prevent misinterpretations the physician should therefore communicate the limitations of these examinations to the seafarers.

For many diseases, treatment is not just an opportunity for accelerated healing. At times it may actually be a necessity for the patient to get better and to preserve a certain amount of function. This, however, does not always apply for musculoskeletal disorders, many of which may have a chronic course and involve tissue degeneration for which little or nothing can be done.

Tendinitis, bursitis and other upper limb conditions

The terms tendinitis and tenosynovitis represent painful inflammatory conditions that – similar to afflictions of tendinous insertions – may be provoked by the straining of a tendon, especially during tasks to which the seafarer is unaccustomed. Active use of the tendon will be painful, and there may be local heat and redness. Inflamed synovial membranes will also be associated by swelling and crepitation. Tendinitis may occur in any tendon, but in an occupational context the occurrence is mostly at the volar or dorsal wrist or involve the extensor pollicis brevis and abductor pollicis longus muscles (de Quervain’s syndrome). Trigger finger may occur with a stenosing tenosynovitis of a flexor tendon.

In epicondylitis changes are mostly degenerative rather than inflammatory and located at the tendinous insertion on the bone (tendinosis). There will be local pain with pressure at the tendon/insertion. The function of the bursae is to fender off the motion of tendons and muscles near to the large joints such as the elbow or knee. During strong and repetitive strain, the pouches may produce fluid and painless or tender swelling may or may not be accompanied by signs of inflammation. Both conditions require rest and often immobilization. To prevent relapse it is essential to identify the cause of the disorder.

Example 1: Lateral epicondylitis or "tennis elbow" is characterized by elbow pain provoked by vigorous use of the hand. There is tenderness at the insertion of wrist extensor muscles on the lateral epicondyle where wrist extension provokes pain. Micro-lesions in the tendinous insertion at the epicondyle may occur during a fierce passive stretch or similar hard impact, such as prolonged or intense use of a heavy hammer. Such pathology, however, would not be expected by simple repetitive work, unless it has been extremely powerful. Since nerve afflictions such as radial tunnel syndrome or pectoralis minor syndrome are important differential diagnoses, neurological signs should be sought from the neck and include the whole limb. Lateral epicondylitis and radial tunnel syndrome may co-exist in the same patient. The pain should not be provoked and powerful strain of hand and forearm should be avoided.

Example 2. Rotator cuff disorders may be located in tendons and bursae, and may also involve other structures such as nerves in the vicinity of the shoulder joint. Shoulder pain was reported by 60% of Swedish fishermen.8 An increased hospitalisation rate has been reported in fishermen.11 Rotator cuff syndrome often consists of a supraspinatus tendinitis, but may also be located to other parts of the cuff such as, e.g. the long biceps tendon or the infraspinatus tendon. Since the perfusion pressure in the supraspinatus tendon drops to 0 with even minor shoulder abduction, static work with the arm away from the body is a risk factor for degenerative tendon changes. Likewise, physically demanding work may reduce the perfusion of tendons and contribute to the physiological age-related degeneration, which may thus facilitate inflammation with shoulder strain. Therefore rotator cuff tendinitis would be expected to be much more frequent among elderly seafarers – in particular those that have experienced many years of sustained and heavy physical work. A not unusual exception is when the subacromial space is reduced and the tendon therefore compressed, such as may result from compromised scapulae stability with a drooping and/or inwards rotated shoulder.

As with other tendon-related pathology there is tenderness over the injured tendon/insertion, and pain will be provoked by powerful use of the associated muscle. A “pain arc” is a characteristic feature with supraspinatus tendinitis, i.e. pain, which increases by abduction to the horizontal level and then decreases again on further abduction. With a reduced subacromial space, collision during the impingement-maneuver provokes the pain. A positive drop-arm test signifies a rotator cuff rupture. With reduced passive movement in the glenohumeral joint a frozen shoulder/periarthritis is likely. This is best examined by assessing the upper arm outward rotation with the upper arm close to the body.

It is obviously not good enough to equate shoulder pain with a disorder of the rotator cuff. Many patients, who are interpreted as suffering from rotator cuff syndrome, do not meet the above requirements for the diagnosis of a rotator cuff tendinitis.

It is obviously important to identify the nature of the diseased tissue. Consequently, the physical examination should not only focus on the tendons and insertions, bursa, and insertions but also on bone and nerves. Therefore, besides inspection, assessment of pain provocation at certain movements and local tenderness, the neurological aspect should be carefully studied, including an estimation of the power of representative individual muscles and the sensibility in selected homonymously innervated areas of the skin. If looked for in patients with shoulder and/or upper limb pain, neurological abnormalities suggesting an involvement of the brachial plexus or other parts of the upper limb nerves are frequent. By shoulder asymmetry with a drooping shoulder – for example due to constraints such as a poor agonist-antagonist balance – or with a bony prominence, e.g. caused by an osteophyte in the acromioclavicular joint (osteoarthritis in this joint is frequent and may be related to physical strain)16 may compromise the available subacromial space and lead to impingement. The pain in rotator cuff syndrome should not be provoked, and the arm should be used near the body.

Example 3. Upper limb symptoms related to computer work, which is increasingly integrated in the maritime working environment, e.g. on the bridge and in the engine room, include pain that may be located anywhere in the upper limb and move between different locations. The pain is frequently of a neuropathic nature and accompanied by peripheral paraesthesia and subjective weakness.

When working with a computer mouse or keyboard, the arm is extended forward and the forearm is kept in almost maximal pronation. At the same time the operator performs static-repetitive flexion and extension of fingers and fine static shoulder movements in the horizontal plane. Therefore certain forearm muscles (m. supinator) are stretched while others are shortened (m. pronator teres). Around the shoulder, the rhomboid and trapezius muscles are stretched while other muscles are contracted and shortened (pectorals). A tense muscle can tighten over one or more nerves with a pressure that exceeds their capillary perfusion. The risk of disease is likely to be increased by intensive work or suboptimal ergonomic conditions.

A neurological examination can identify weakness in muscles innervated distal to the brachial plexus and associated characteristic sensory changes. One should not expect complete paralysis, but only minor pareses. Similarly, one should not expect analgesia or anaesthesia in the investigation of cutaneous sensibility, but only minor changes such as slightly reduced, increased or just altered sensation. In more severe cases there may be allodynia, which is a condition where stimuli that are normally non-painful such as touch, cold or vibration leads to pain.

Management. Generally, upper limb disorders are said to represent an inflammation that can be managed by anti-inflammatory medication, by sparing the limb, and by ensuring that the inflamed structure is not being provoked so that the inflammation is maintained. Conversely, anti-inflammatory treatment does not help in the absence of inflammation. Neuropathic pain should also not be provoked – meaning the there will be a pain that is worse after than before and during use of the arm. As much variation in activities as possible would favour most upper limb conditions. The limb should be used without force and be kept close to the body. Training – e.g. of weak muscles should be done cautiously and only with the aim to restore muscular balance. Muscles that are weak due to an affliction of its innervating nerve should not be trained. Attempts to do so, e.g. in the gym or by swimming will exacerbate the condition. Painful training may be a serious risk factor, in particular with neuropathic conditions, and it is important to draw attention to this, because many patients with upper limb disorders follow their doctors' well-intentioned advice about training with weights or swimming, and because many patients often believe that pain "must be worked out". It may be important to stretch tightening structures to reduce tension and promote tissue mobility, including the mobility of nerves, and some physiotherapists are good at it. Ergonomic adjustment aiming to counteract relapse should always be undertaken.

Osteoarthitis

Osteoarthritis is extremely common. It may be a “primary” idiopathic condition or it may develop “secondary” to individual constitution or external exposure such as large body weight, work, or injury. Meta-analyses have demonstrated the relation of knee-osteoarthitis to kneeling, squatting, heavy lifting, and apparently also to climbing stairs or ladders.17 Osteoarthritis of the hip is related to heavy lifting while the relation to climbing stairs or ladders has not been demonstrated.18 The prevalence rises with age. In actively working people such as e.g. fishermen and deck crew, the most afflicted joints include the acromioclavicular joint,16 the knee,11 and the hip joint.

The disease starts in the cartilage of the joint, but may progress to the adjacent bone and connective tissue. The symptoms include joint pain and stiffness, which is initially present during exercise, and later also on rest. Typically, the pain with osteoarthritis has the character of a “triad” with presence of pain at the start of exercise, e.g. walking, subsequently reduced or absent pain after a while, and then recurring pain after some further distance of walking or other activity. There may be visible changes such as swellings and disfiguration, and movements may be restricted and painful.

A high level of occupational walking and standing is associated with symptomatic knee osteoarthritis, and bending, twisting and reaching are associated with symptomatic hip osteoarthritis.19 Based on meta-analyses, an international study group has concluded that healthy subjects as well as osteoarthritis patients in general can pursue a high level of physical activity, provided that the activity is not painful and does not lead to trauma. In contrast, work activities that produce or maintain pain should be avoided.20

Knee pain was reported by 60% of Swedish fishermen.8 A high proportion of seafarers attending health service for musculoskeletal disorders had knee (29%) and hip (8%) problems.13 In a study of knee pathology, seafarers constituted ¼ of patients in an orthopaedic clinic. Half of them had a diagnosis of knee osteoarthritis, with a predominance of medial compartment cartilage degeneration. 1/3 of the seafarers had genu varus.21 The particular vulnerability of the medial compartment (in contrast to the lateral compartment) may be explained by biomechanical factors, and the apparently increased prevalence among seafarers seems to be related to exposures in the maritime setting such as staying on a moving ship deck and climbing ladders.

Hip and knee replacements are increasingly performed in people in working ages, and the chance of undergoing surgery is increased with paid employment.22 Knee osteoarthritis impairs labour force participation, work attendance and work productivity. Little is known about effective interventions (treatments, work modifications etc.) to improve work participation for persons with knee osteoarthritis or how the type of work affects clinical outcomes following knee replacement. The content of the advice relating to work that should be given to patients following surgery is also disputed. Generally, however, intense and high-impact activities are discouraged.23 Following hip surgery, most patients in working ages are able to return to work but may experience difficulties in climbing stairs, lifting, squatting, kneeling and climbing.24 A meta-analysis has shown that knowledge is sparse regarding beneficial or limiting factors affecting return to work after knee or hip replacement but that the restriction of movement may be a limiting factor.25

Low back pain – lumbago – and pelvic pain

It has been estimated that 37% of the global burden of low back pain is attributed to occupation.26 There is limited knowledge about the frequency of low back pain and its work-relatedness among fishermen and seafarers. However, low back pain was reported by 80% of Swedish fishermen.8 In a Norwegian study 30% of seafarers had pain in the low back, which was the most frequent location of musculoskeletal pain in this sample.4 A high proportion of seafarers that attended health service for musculoskeletal disorders had low back problems (24%).13. The potential work-relatedness of low back pain has been described in a sample of 163 seafarers who attended a clinic in Singapore. The majority were ratings, and most had acute low back pain.27

Non-specific chronic low-back pain as well as pelvic pain is extremely common. The latter is frequently associated with pathology around the sacroiliac joints and the pelvic ligaments. It is frequently overlooked and confused with low back pain.

Lumbago and pelvic pain may be triggered by a sudden, uncontrolled strain, by a strong muscle effort or appear consequent to a traumatic event. In some cases, a ruptured intra-vertebral disc may be signalled by an acute attack of lumbago. The symptoms are sudden with strong pain in the lower back, often greatly restricted movement, the back may appear crooked as a result of cramped muscles and pain, and the affected muscles are tender to pressure. The patient is mostly advised to receive a programme including strengthening back exercises.

Back pain radiating to a limb may be due root compression by a herniated disc or by a narrowed foraminal passage. This manifestation, which is often termed sciatica meaning that neuropathic pain is referred in the sciatic nerve territory, tends to be mostly regarded as root compression. Irradiating leg pain may also be due to an affliction of roots that supply peripheral nerves other than the sciatic nerve, or to compression at any level along the sciatic nerve, e.g. a piriformis syndrome due external nerve affliction by the piriformis muscle

In most cases, however, radiating pain represents a phenomenon (referred pain) secondary to a myofascial or ligamenteous problem in the low back and sacral region.

There are certain characteristics of lower extremity pain consequent to root compression. With manifest root compression, severe pain radiates down the leg and usually below the knee. It is easily provoked, e.g. by elevating the stretched leg. The leg pain is usually worse that the back pain, and is aggravated by specific movements, cough and sneeze. The pattern of muscular weakness, sensory abnormalities and weakened deep reflexes will indicate the level of compression.

A few cases of disc herniation should be viewed as emergencies – notably if there is sudden disappearance of pain with persisting paresis, and/or urine or stool incontinence (cauda equina syndrome). While these conditions should be treated surgically as soon as possible, there is little evidence that other cases of root compression are better treated by surgery than by conservative treatment.

The history and a thorough physical examination can usually rule out "red flags" and therefore obviate the need of radiological studies. These examinations are potentially harmful, they may be costly, and they do not necessarily help the patient. Despite the correlation with age rather than with symptoms, “abnormalities” such as degenerative changes are frequently detected and carefully described by the radiologist. Although, e.g. spondylosis, disc bulges or facet joint arthropathy may be related to symptoms, they are often not, and similar findings are common in non-symptomatic subjects. Still, radiological descriptions frequently turn out to become the “diagnosis” although the pain does not derive from the bony structures but rather from muscles or ligaments.

Degenerative radiological changes (with or without accompanying pain) in the lumbar region can be related to overload but may, however, also occur in people who never had physical work. Their significance must be critically assessed from case to case. Independently of identified degenerative radiological changes, a seafarer may develop back pain consequent to future trauma or cumulative impact on the back that may or may not be radiologically visualized.

The seafarer with mild uncomplicated lumbago, without red flags suggesting serious underlying disease, and most seafarers with degenerative X-ray low back changes should continue working. There is no indication that the seafarer will experience fewer symptoms if relieved from duty with normal use of his back. In fact, despite the absence of differential treatment guidelines based on degenerative radiological changes it is reasonable in most patients to expect reduced pain by continuation of the normal daily activity. Inactivity and sick leave are usually unnecessary and can be harmful. Evidently, however, it can be argued, that the seafarer with major back symptoms should discontinue exposure to heavy lifting, awkward postures and/or movements. There is no reason to trouble the seafarer with back pain further. However, suspending the contact with the workplace may cause isolation and undue concern over the future health of the back. Even though the back can be used normally in spite of back pain, many fear ending up  disabled. Fortunately, this is a rare occurrence – and when it happens, it may rather relate to well-intentioned medical interventions than to the lack of those.

Most doctors are aware of this newer understanding, which has contributed to better help to the low back patient. Still, however, sick leave remains unnecessarily the common treatment of an uncomplicated back disorder, and low back pain remains one of the dominant reasons for sickness absence. The patients are typically treated with NSAID’s and referred to physiotherapy and/or an x-ray of the spine. With continuing complaints, referral to a specialist and MRI will frequently be the next steps. None of these are necessarily indicated.

If the doctor lets the patient understand that the pain is caused by a radiologically demonstrated degeneration, the patient perceives that his back is "worn out", often as the result of a heavy work. The seafarer expects serious consequences of further loading of the back because, unless the back is spared from strain, the radiological changes and the low back disorder are expected to get only worse. Such a "diagnosis" that clarifies the situation to the patient may be convenient for the physician. But without careful clinical examination the real explanation may be overlooked, and the easy explanation rarely benefits the seafarer.

When sick leave has been accepted as a treatment, it is hard to get going again as long as the pain continues. And if sick leave was indicated in the primary stage - why not later if the pain persists? Better alternatives to sick leave will be an agreement on the ways of accommodating the patient at the workplace, which is often willing to comply with the physician’s advice – particularly when the likely alternative could be a lengthy sick leave.

The seafarer must be able to tell his story, to accept his pain and to be thoroughly physically investigated. Obviously, paraclinical investigations such as MR-scanning may in certain situations provide diagnostic assistance but should, however, never replace a thorough physical examination. After a detailed physical examination most seafarers can be re-assured that their condition is not serious, and neither requires imaging, prescription medication, nor sick leave. It must be understood and accepted that the back should be used but not abused, that activity is mostly much better than inactivity, and that back exercises or training of proprioception by coordination and balance exercises, e.g. with great balls or rocker boards can be the right treatment of lumbago or pelvic dysfunction, respectively – even despite the pain. Pain at work, which is not associated with particularly heavy loads or difficult positions, must be accepted as it is and treated by back exercises. But the removal of unhealthy work-exposures would tend to positively influence the course and also tend to benefit work colleagues in whom unnecessary work-related pain should also be avoided.

Raynaud’s phenomenon

Attacks of white fingers involving one or several phalanges of one or several fingers are frequent. This condition is mostly idiopathic but may also arise secondary to an autoimmune condition or to prolonged occupational exposure to vibrating tools (so-called hand-arm-vibration syndrome, or traumatic vasospastic syndrome). There is also some evidence that thermal trauma to blood vessels for example from frostbite may play an etiological role.28 Climatic exposures such as cold and humidity are prevalent with deck work in the maritime setting and may together with smoking, which is also frequent in the maritime population, aggravate and trigger Raynaud’s phenomenon. The majority of persons with hand-arm vibration syndrome have abnormal cold sensitivity.

Raynaud’s phenomenon may persist for a long time or may improve spontaneously. An increased hospitalisation rate has been found in the maritime population12 suggesting the chronic character of the condition and the particular difficulties seafarers with the disease may experience when exposed to cold and local vibrations.

There are various measures, which can help the condition. Smokers should stop because nicotine can further impair circulation by constricting blood vessels. Activities known from experience as likely to trigger an attack should be avoided (local vibration, exposure to cold and humidity). Warm gloves are helpful and swinging the arms around during an attack may help to restore a normal finger-circulation.