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Soft tissue anatomy

This is an excerpt from Clinical Guide to Surface Palpation 2nd Edition With HKPropel Online Video, A by Michael Masaracchio & Chana Frommer.

Several groups of muscles surround the elbow and forearm.

  • Anteriorly, the elbow flexors consist of the biceps brachii, brachialis, and brachioradialis.
  • Posteriorly, the triceps brachii and anconeus compose the elbow extensor group (figure 5.3).
  • The medial elbow is covered by the flexor–pronator group of muscles.
  • The lateral elbow is occupied by the extensor–supinator group of muscles.

Figure 5.3 Muscles of the arm.
Figure 5.3 Muscles of the arm.

Anatomically, these muscle groups are separated into layers, and knowing the relative depth of these muscles during palpation is an important consideration so that proper force can be applied for structure identification.

The posterior forearm is divided into two layers:

  • The superficial layer contains the brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris (figure 5.4, superficial).
  • The deep layer is composed of the supinator, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and the extensor indicis (figure 5.4, deep).

All muscles of the posterior forearm are innervated by the radial nerve.2

Figure 5.4 Posterior forearm muscles.
Figure 5.4 Posterior forearm muscles.

The anterior forearm muscles are broken into superficial, intermediate, and deep layers (figure 5.5).

  • The superficial layer consists of the pronator teres, flexor carpi radialis, palmaris longus, and flexor carpi ulnaris.
  • The intermediate layer consists of the flexor digitorum superficialis.
  • The deepest layer consists of the flexor digitorum profundus, the flexor pollicis longus, and the pronator quadratus.

Figure 5.5 Anterior forearm muscles.
Figure 5.5 Anterior forearm muscles.

It should be pointed out that certain anatomy textbooks consider the anterior forearm in four layers, which the primary author of this text would agree with. This is because the pronator quadratus is located deep to the flexor pollicis longus and flexor digitorum profundus.

These muscles produce movement of the elbow, forearm, wrist, and hand and provide dynamic stability to all these joints. The anterior forearm muscles are innervated by the median or ulnar nerve or both.2

The muscles surrounding the elbow and forearm form a bordered space known as the cubital fossa. This triangular-shaped depression has a medial border, a lateral border, and a base.

  • The medial border is the pronator teres.
  • The lateral border is the brachioradialis.
  • The base is an imaginary line between the medial and lateral epicondyles.

The floor of the cubital fossa is the brachialis muscle, which lies directly over the elbow joint. The cubital fossa contains the biceps tendon, radial nerve, median nerve, and brachial artery.2

  • In addition to the muscles crossing the elbow joint, the capsule and several ligaments add passive stability to these joints (figure 5.6).
    • The medial and lateral aspects of the elbow are reinforced by the ulnar (medial) collateral ligament and the radial (lateral) collateral ligament, respectively.1,2
    • The ulnar collateral ligament runs from the medial epicondyle of the humerus to the coronoid process of the ulna and resists valgus (abduction) forces
    • The radial collateral ligament runs from the lateral epicondyle of the humerus to the radial head and resists varus (adduction) forces.1,3-5
  • The proximal radioulnar joint is reinforced by the thick annular ligament. This ligament is responsible for holding the radial head in the radial notch of the ulna during pronation and supination of the forearm.1,2

Figure 5.6 Ligaments of the elbow.
Figure 5.6 Ligaments of the elbow.