The experience of being woken up or kept awake by shoulder pain, often centered on the deltoid muscle, is a common and frustrating issue. This pain, which can feel like a deep ache or burning sensation, intensifies when the body is at rest. The pain rarely originates in the deltoid muscle itself, but rather from an underlying condition in the shoulder joint that is aggravated by nighttime positioning. Understanding the mechanical forces at play during sleep helps explain why this pain often peaks at night.
Understanding the Deltoid Muscle and Common Pain Sources
The deltoid muscle is a large, triangular muscle that covers the shoulder joint, providing the rounded contour. It is functionally divided into three heads: the anterior, medial, and posterior deltoids. Its main roles include stabilizing the shoulder and initiating arm abduction (lifting the arm away from the body).
Pain felt in the deltoid area often originates from issues in the deeper structures that the muscle overlies, such as the rotator cuff tendons or the bursa. Common underlying conditions include rotator cuff tendinopathy (irritation of the stabilizing tendons) and subacromial bursitis (inflammation of the fluid-filled sac that cushions the joint). These inflammatory conditions cause pain that radiates outward, making the deltoid muscle feel painful even though it is not the primary source of the problem.
How Sleeping Positions Worsen Deltoid Pain
The intensification of deltoid pain during sleep is directly related to the mechanical stress and inflammatory changes that occur when the body is horizontal for long periods. Side sleeping, especially on the affected shoulder, is a major contributor to this problem. Lying directly on the side compresses the soft tissues within the shoulder joint, which can lead to shoulder impingement.
This compression pinches the bursa and the rotator cuff tendons, increasing pain from pre-existing inflammation. Sleeping on the affected side also reduces blood flow to the compressed tissues, a state known as ischemia, which can heighten pain signals and prevent the flushing of inflammatory compounds.
Even when sleeping on the unaffected side, the painful shoulder can still be aggravated. Gravity pulls on the joint capsule and surrounding tendons, causing a subtle stretch that increases internal pressure and discomfort. The sustained, static position of the arm during sleep also prevents the natural movement and circulation needed to dissipate inflammation accumulated during the day.
Actionable Steps for Nighttime Relief
Positional Adjustments
Immediate relief from nighttime deltoid pain often requires strategically altering sleeping positions. The most important strategy is strictly avoiding sleeping directly on the painful shoulder, which maximizes soft tissue compression. Sleeping on the back is generally the most recommended position because it distributes body weight evenly and prevents direct pressure on the joint.
For back sleepers, placing a small pillow or rolled towel underneath the elbow of the affected arm helps keep the shoulder in a neutral, slightly externally rotated position. This reduces tension on the tendons and joint structures. If side sleeping is unavoidable, lie on the non-painful side and hug a pillow against the chest. This prevents the painful shoulder from slumping forward and internally rotating, which narrows the joint space.
Pre-Sleep Routines and Support
Before attempting to sleep, applying a targeted cold pack to the painful area for about 15 minutes can help reduce local inflammation and numb pain signals. Taking an over-the-counter Nonsteroidal Anti-Inflammatory Drug (NSAID), such as ibuprofen or naproxen, can also provide temporary relief by decreasing inflammation. Choosing a medium-firm mattress that provides adequate contouring for the shoulder can also make a difference, as mattresses that are too soft or too firm can create excessive pressure points.
Seeking Diagnosis and Long-Term Treatment
If the deltoid pain persists for more than a few weeks, becomes sharp, or is accompanied by weakness or restricted range of motion, consult a healthcare professional. Persistent nighttime pain indicates a more significant underlying issue, such as a partial rotator cuff tear, chronic bursitis, or shoulder impingement syndrome.
The diagnostic process begins with a physical examination to test range of motion and strength, followed by imaging studies. X-rays rule out bony issues like arthritis or fractures, while a Magnetic Resonance Imaging (MRI) scan visualizes soft tissues to confirm a diagnosis like a tear or severe inflammation.
Long-term treatment focuses on addressing the root cause of the joint irritation. Physical therapy strengthens the rotator cuff muscles to improve joint stability and prevent the upward migration of the humerus that causes impingement. For severe inflammation, a doctor may recommend a corticosteroid injection, which delivers anti-inflammatory medication directly into the joint space. In rare cases involving a severe, non-healing tear or chronic impingement unresponsive to conservative care, surgical intervention may be necessary.