On the beach, never swim where a red flag is flying; a danger to life exists. In medicine, never ignore a ‘red flag’ symptom or sign: a danger to life or limb exists. These clinical features are shown in Table 1.2. Emergency diagnoses in the locomotor system and the danger to which attention is drawn are listed in Table 1.3. Clinicians frequently misdiagnose rare but dangerous conditions. In the early stages of such disorders, the clinical features may be similar to more common self-limiting conditions. Later, there is no excuse for missing an obvious swelling.

Table 1.2 Clinical ‘red flag’ features suggesting serious pathology

Symptom	Corresponding Sign
Pain preventing sleep	’Drawn’ facial appearance
Loss of appetite	Loss of weight
Temporal headache and blurred vision	Visual loss
Loss of bowel and bladder control	Saddle anaesthesia, bilateral lower limb neurology
Other signs
Rapidly progressive symptoms	Bilateral upper motor neurone signs
Painful swelling	Fever >38°C
Red, hot swollen joint	Inability to bear weight through a joint

Table 1.3 Emergency diagnoses and dangers in musculoskeletal patients

Diagnosis	Danger
Tumour	Loss of life or limb
Infection	Bone or joint destruction
Central cord compression	Limb/bladder/bowel dysfunction
Cauda equina syndrome	Bladder/bowel dysfunction
Giant cell arteritis	Blindness
Slipped upper femoral epiphysis	Early hip arthritis

The absence of a traumatic cause for one or more of these clinical features should provoke suspicion, and stimulate further investigation. Patients who volunteer previous trauma, however, should not be ignored, even if the X-ray is normal. Parents of children with bone tumours, for example, frequently describe an earlier bruise or football injury that ‘went on to become a painful lump’. It is important for the alert clinician to believe their own examination findings, and act on them. This will often lead to an early diagnosis and a better patient outcome.

Malignancy

Malignant tumours of bone and soft tissues are aggressive and, therefore, grow rapidly. Features indicative of malignant potential include lesions that are:

• rapidly growing

• more than 5 cm in size

• painful

• deep to deep fascia.

These lesions should be viewed as a potential malignant tumour until proven otherwise. Even one or two of these features should provoke early investigation. A delay of weeks will compromise treatment options and survival.

Infection

Features of bone and joint infection are those of local inflammation. This can be masked in the immunosuppressed, and infection should be part of the differential diagnosis in a patient with a musculoskeletal swelling who is unwell, on immunosuppressive therapy or suffering from an immunodeficiency disorder. In non-immunosuppressed children, clinical features predictive of osteomyelitis or septic arthritis include:

• inability to weight-bear

• temperature >38°C

• leukocyte count >12 000×109 per litre

• erythrocyte sedimentation rate (ESR) >40 mm/h

• raised C-reactive protein (CRP) level.

As in potentially malignant tumours, even one or two of these features should provoke early investigation. A delay of hours or days will lead to established infection, with bone or joint destruction and more extensive surgical reconstruction required later.

Spinal disorders

Symptoms predictive of potentially serious spinal pathology are as above; additional features identified by the Royal College of General Practitioners are:

• presentation under age 20 or over age 55 years

• non-mechanical pain

• thoracic pain

• past history of carcinoma, steroids, human immunodeficiency virus

• widespread neurological symptoms

• structural deformity.

Signs of an ‘upper motor neurone’ lesion indicating central cord compression include hypertonic weakness and rigidity, brisk reflexes and sustained clonus. Causes include spinal infection (pyogenic or tuberculosis), tumour, cervical vertebral subluxation secondary to trauma or rheumatoid arthritis, or a cervical or thoracic central disc prolapse. Symptoms of sphincter and gait disturbance with saddle anaesthesia are highly suggestive of cauda equina syndrome, requiring an urgent magnetic resonance imaging scan for confirmation of central disc prolapse and appropriate urgent spinal decompression.

Giant cell arteritis

When this form of vasculitis affects the temporal artery it is known as ‘temporal arteritis’ and can occasionally produce ciliary artery occlusion, leading to blindness. Symptoms of polymyalgia rheumatica should prompt questions about temporal pain and blurred vision, and examination for temporal tenderness. If these features are present then steroids should be commenced and an immediate rheumatological referral made to include temporal artery biopsy.

Slipped upper femoral epiphysis

A mild form of this condition of late childhood and adolescence is important to identify early for the prevention of complete slip and a uniformly poor outcome. Acute groin, thigh or knee pain and difficulty in weight-bearing on that limb should suggest the possibility of hip pathology. An inability to weight-bear should result in an immediate orthopaedic referral. The typical description is of an older boy with an externally rotated leg and unable to bear weight on the affected side being supported by two parents. In an adolescent, a radiograph in the antero-posterior and (especially) lateral planes might reveal a slip of the proximal femoral epiphysis. Long-term prognosis depends upon the degree of slip. Even in those able to walk, persistent limp or pain for longer than a week should be investigated promptly to avoid a progressive ‘acute on chronic’ slip.

Summary

‘Red flags’ are key symptoms and signs that alert the clinician to the possibility of serious disease. To elicit them early is of vital importance to a satisfactory patient outcome.

Examination of limbs

A good general format of examination of the musculoskeletal system is the GALS (gait, arms, legs and spine) method to ensure that the entire musculoskeletal system is included in the examination. For each individual joint examination it is best to adopt a systematic approach using ‘Look, Feel, Move and Special Tests’ as outlined below (Table 1.4).

Table 1.4 Important points to observe in joints during clinical examination

Look	Scars, sinuses, swelling, deformity and erythema
Feel	Skin, soft tissues and joint
Move	Active and passive; normal range, reduced or increased range of movement; and stress tests
Special imaging (see Chapter 4 on Imaging)	Plain X-rays are the mainstay
	MRI gives good definition of non-osseous structures
	Ultrasonography is useful for joint effusions and rotator cuff tears of the shoulder
	Arthrography is used to confirm reduction of a hip in a child