Muscles of Extremities

Learning & Test Objectives

  1. General anatomy of muscles.
  2. Arrangement of muscles within their compartments enclosed by fasciae.
  3. Origin and insertion, innervation, and function of muscles. 
  4. Topography of nerves and vessels of the limbs. 
  5. Identifying and drawing structures observed on cross-sections of the limbs. 

Description of the test

The test is held by the general rules of written tests (see Continuous Testing – Organisation).

The test Muscles of the extremities follows the general rules of written tests (see Continuous Testing – Organisation). The test is mainly focused on the muscles of the extremities, their attachments (origin, insertion), functions and innervations. The test may also contain questions on general myology, fasciae of the extremities, arches of the foot, radiological images of the bones and joints of the extremities and selected clinical and other interesting notes. There may also be a few basic questions on neural plexuses, nerves, vessels and topographical regions. It is necessary to know the spinal segments which form the main nerves of the extremities. Test participants will be required to draw and described one of the required schemes. The list of required schemes of muscles of the extremities can be found at the bottom of this page.

Clinical notes

Hypertonia means increased muscle tone. It can have either an organic or a functional etiology. Hypertonic muscles are not able to fully relax.

Hypotonia and atonia may be caused by peripheral nerve damage.

Compartment syndrome is a pathological condition caused by increased intrafascial pressure, which can occur in a number of situations such as contusion causing soft tissue oedema or by compression from incorrectly applied plasters. It leads to impairment of the macrocirculation and microcirculation with subsequent development of irreversible ischemic changes and disintegration of muscle fibers (rhabdomyolysis).

Myofascial trigger points are pathological indurations inside a muscle. They are usually palpable and are characterised by increased irritability and pain. External pressure on the trigger point causes pain and twitching and even contraction of the surrounding muscles.

Golfer's elbow is an overuse injury of the flexors that originate on the medial epicondyle of the humerus. It can be caused by manual labor and is characterised by pain over the medial epicondyle of the humerus.

Tennis elbow is an overuse injury of the extensors that originate on the lateral epicondyle of the humerus. It can be caused by working on computers for long periods of time and is characterised by pain over the lateral epicondyle of the humerus.

Hypertonus in the adductor pollicis often occurs with the spasmodic type of grasping or holding of a burden (e.g. texting on a mobile phone).

Tendosynovitis is an inflammation inside the tendon sheath associated with pain, swelling and movement limitation. The condition can be caused by muscle overload.

The iliopsoas courses very close to the internal organs. Thus pathology of the iliopsoas may mimic a disease in the internal organs. When the right iliopsoas is injured, pain is felt in the right lower quadrant which can mimic appendicitis. Hypertrophy of the iliopsoas can make passage through the colon difficult.

Walking uphill, upstairs or jumping is not possible when the gluteus maximus muscle is injured.

The biceps femoris muscle is often injured (stretched or torn) during sprinting disciplines and sports games.

Trigger points in the tibialis anterior muscle cause pain on the ventromedial surface of the ankle and on the dorsal and medial surfaces of the great toe. The trigger points are usually situated in the proximal third of the muscle and they are very painful. They can be caused by driving for long periods of time with high-positioned pedals.

Pain from the soleus muscle is located in the whole area of the heel, the calcaneal (Achilles) tendon and the ipsilateral sacroiliac joint. Such pain is quite common for recreational runners.

Axillary nerve palsy can occur due to a fracture of the surgical neck of the humerus. It manifests as impaired abduction of the arm and predisposes to subluxations of the shoulder due to instability of the head of the humerus.

The median nerve can be damaged in the pronator canal but most commonly in the carpal canal (tunnel), which results in carpal tunnel syndrome. Shoulder dislocation and stab and bullet wounds can damage the nerve in the axilla. Colles' fracture and slash wounds on the wrist may damage the nerve in the forearm. Damage to the median nerve results in impaired pronation of the forearm (pronator teres and quadratus muscles), impaired opposition and flexion of the thumb (opponens pollicis muscles and the deep head of the flexor pollicis brevis muscle) and impaired flexion of the second and third finger. Flexion of the fourth and fifth finger is preserved, due to the part of the flexor digitorum profundus muscle innervated by the ulnar nerve. The clinical sign is called the ‘benedict hand or preacher's hand’.

The ulnar nerve is most commonly harmed in narrow anatomical spaces such as the cubital and ulnar canals. Fractures of the elbow and forearm often damage both the ulnar and median nerves. Injury to the ulnar nerve results in an impairment in motor function giving rise to the clinical appearance of a ‘claw hand’.

Radial nerve injuries are fairly common. They are usually caused by fractures of the middle part of the humerus affecting the groove for the radial nerve – radial canal (Holstein-Lewis fractures). Fractures of the forearm may also affect the radial nerve. Radial nerve injuries manifest as an absent the tricipital reflex and weakness in elbow extension. Another prominent sign of radial nerve palsy is an inability to extend the wrist causing a condition called ‘wrist drop’.

Damage to the tibial nerve usually occurs in the malleolar canal and can result from cut wounds, ankle fractures and incorrectly applied plasters. It presents as impaired plantar flexion (an inability to stand on tiptoes) due to impaired function of the triceps surae muscle. The ankle jerk reflex is absent. Due to the predominance of the un-antagonised dorsal flexion of the tibialis anterior muscle, the heel is the first part of the foot to touch the ground while walking. This results in a syndrome called ‘club foot’ (pes calcaneus).

The fibular nerve is covered only by skin where it lies near the head of the fibula. In this location the nerve is most vulnerable to trauma and compression from incorrectly applied casts. Dislocations and sprains of the knee may also harm this nerve. The anterior muscles of the leg become impaired, resulting in a ‘flapping foot’ and an inability to stand on the heels. The arches of the foot gradually deteriorate due to dysfunction of the fibularis longus muscle.
 

Other interesting notes

Compartment (compartimentum) is a space containing a group of muscles firmly bounded by fascia.

Skeletal muscle cell is 40–80 µm thick and its length ranges from millimetres to centimetres.

A diploneural muscle is a muscle innervated by two peripheral nerves. A plurineural muscle is a muscle innervated by more than two peripheral nerves.

Fixed point (punctum fixum) is a part of muscle insertion which is reinforced (via influence of shortening activity of other muscles) so that the other insertion part of muscle – mobile point (punctum mobile) could perform movement in particular joint.

The flexors and supinators of the forearm are more dominant than the extensors and pronators. The flexors and supinators may shorten during long periods of inactivity, as occurs in bedridden patients.

Tendinous chiasm (chiasma tendinum) means crossing of tendons. This occurs at the middle phalanges as the tendons of the flexor digitorum profundus muscle pass through the bifurcated tendons of the flexor digitorum superficialis muscle to insert on the distal phalanges.

The dorsal aponeurosis (aponeurosis dorsalis) is a fibrous structure on the back of the fingers, which attaches to the middle and distal phalanges. The extensors of the hand/foot, lumbricals and interossei muscles insert on the phalanges through the dorsal aponeurosis.

The iliopsoas muscle is necessary for walking. The muscle also fixes the supporting limb. In a standing position the muscle prevents the torso from falling backwards and increases the lumbar lordosis. Permanent asymmetry can cause deviation of the vertebral column.

The major pes anserinus (‘goose foot’, pes anserinus major) is the insertion of the conjoined tendons of the sartorius, gracilis and semitendinosus muscles on the medial condyle of the tibia.

Hamstrings is a common term for the semitendinosus muscle, semimebranosus muscle and the long head of the biceps femoris muscle.

The fibularis tertius muscle is a part of the extensor digitorum longus, which inserts on the tuberosity of the fifth metatarsal by a slim and often doubled tendon.

The Achilles tendon is a term for the calcaneal tendon.
 

Pictures to draw

Transverse section of the arm

Transverse section of the forearm

Transverse section of the hand

Transverse section of the thigh

Transverse section of the leg

Transverse section of the foot


 

Radiographical images

Radiographs of the bones and joints of the upper extremity

Radiographs of the bones and joints of the lower extremity

Created: 6. 11. 2016 / Modified: / Responsible person: MUDr. Azzat Al-Redouan