Observe the symmetry and shape of muscles for evidence of hypertrophy, wasting, abnormal shape (e.g. torn tendons and contractures) and abnormal movement. Palpation of muscles allows the assessment of tone and also localisation of symptomatic and unsuspected tenderness. Hypotonia may be present in muscle wasting disease (myotonia or peripheral nerve injuries) and hypertonia in established upper motor neurone disease.
Muscle bulk is related to age, sex, physical activity and to nutritional status. Atrophy may indicate primary muscle disease or peripheral nerve damage. Measurement of the amount of wasting can be obtained with a tape measure, comparing two limbs or by repeated measurements after a timed interval. Measure the circumference at set distances from a bony landmark such as the tip of the shoulder in the upper arm, the olecranon for the forearm and the tibial tubercle for the thigh and calf (figure 1a–g).
The small muscles of the hand provide an early indication of general muscular wasting, as well as peripheral nerve injury. This is seen particularly on the dorsum of the hand, with loss of substance of the interossei of the thumb and index finger, and loss of muscle bulk deep to the long extensor tendon (figure 2a,b).
Local causes of muscular wasting in the hand include carpal tunnel syndrome, lesions of the median and ulnar nerves and their roots, motor neurone disease, poliomyelitis, syringomyelia, peripheral neuropathy and rheumatoid arthritis. If the hands are placed with their palms together, and then back-to-back, the thenar and hypothenar muscles can be compared on the two sides (figure 3a,b). The adductor pollicis facilitates downward pressure in a thumb grip, ulnar nerve damage can be highlighted by deficiency of this movement (Froment’s sign – figure 4), flexor pollicis is used to compensate for the deficit.
At some sites, peripheral nerves can be palpated for thickening and associated tenderness (e.g. the ulnar nerve behind the medial epicondyle of the humerus and the common peroneal nerve over the neck of the fibula); this is a diagnostic feature of leprosy. Tapping along the course of a nerve may give an indication of the site of damage (over the median nerve at the wrist in carpal tunnel compression) or the level to which regeneration has taken place after nerve transection (Tinel’s sign).