**Question:** All of the following features can be observed after the injury to axillary nerve, EXCEPT?

A. Loss of mobility in the shoulder joint
B. Loss of sensation in the upper arm
C. Loss of muscle strength in the forearm muscles
D. Loss of sensation in the shoulder girdle region

**Core Concept:**
The axillary nerve is a peripheral nerve that plays a crucial role in the innervation of the shoulder joint and upper arm muscles. It arises from the brachial plexus, which is a network of nerves formed by the union of spinal nerves C5, C6, C7, C8, and T1. When the axillary nerve is injured, various functional impairments can occur, such as loss of muscle strength in the upper arm and shoulder joint mobility loss. However, the axillary nerve does not directly innervate the shoulder girdle region or forearm muscles, and therefore, the correct answer should address these specific features.

**Why the Correct Answer is Right:**
The correct answer, D - Loss of sensation in the shoulder girdle region, is right because the axillary nerve does not innervate this area. Sensory innervation to the shoulder girdle region comes from the interscapular branch of the sympathetic chain and the suprascapular nerve, which arises from the posterior cord of the brachial plexus.

**Why Each Wrong Option is Incorrect:**
A. Loss of mobility in the shoulder joint: Axillary nerve injury can lead to loss of mobility in the shoulder joint due to the involvement of the deltoid muscle, which is one of the primary muscles responsible for shoulder joint movement.
B. Loss of sensation in the upper arm: Although the axillary nerve does carry sensory fibers, it primarily innervates the upper arm muscles, and the injury would primarily cause muscle weakness rather than loss of sensation.
C. Loss of muscle strength in the forearm muscles: The axillary nerve does not directly innervate the forearm muscles; the ulnar nerve and radial nerve are primarily responsible for forearm muscles. Therefore, an axillary nerve injury would not typically result in loss of strength in the forearm muscles.

**Clinical Pearl:**
The axillary nerve is an essential structure to understand for physicians, surgeons, and other healthcare professionals involved in diagnosing and treating patients with plexopathies. The axillary nerve is a crucial element of the brachial plexus, providing motor and sensory innervation to the upper limb. Understanding the anatomy and functional roles of the axillary nerve and its connections can help guide clinical decision-making and treatment strategies for patients with axillary nerve injuries or disorders.