Shoulder pain that intensifies when lying down or attempting to sleep is a common complaint. This nocturnal discomfort often disrupts sleep cycles. Understanding why the shoulder joint becomes more painful at night involves mechanical, chemical, and biological factors that change when the body is horizontal. This pattern of pain signals that underlying shoulder tissues, such as tendons or fluid sacs, are inflamed or compromised.
Why Lying Down Makes Shoulder Pain Worse
When transitioning from an upright posture to lying down, the physics of the body changes, directly impacting the shoulder joint. During the day, gravity slightly decompresses the space beneath the acromion. When lying flat, this gravitational decompression is lost, which can cause tendons and bursa to settle in a position that irritates existing injuries.
Lying directly on the affected side compresses sensitive soft tissues between the mattress and the bone, increasing pain signaling. Even when resting on the unaffected side, the painful shoulder often falls forward and inward into an internally rotated position. This internal rotation strains inflamed tendons and capsules, contributing to the ache that wakes people up.
The body’s stillness at night allows inflammatory mediators to pool around the injured area. During daytime activity, movement helps circulate these substances away from pain receptors. The lack of movement during sleep leaves a higher local concentration of these chemicals, sensitizing the nerves in the joint.
Biological factors also play a role through the body’s internal clock, or circadian rhythm. The sleep-regulating hormone melatonin, which rises at night, may influence pain pathways. Melatonin can stimulate specific receptors in the inflamed shoulder tissue, potentially contributing to the nocturnal spike in pain experienced by individuals with conditions like frozen shoulder or rotator cuff tears.
Specific Causes of Nocturnal Shoulder Pain
One of the most frequent causes of night pain is an injury to the rotator cuff. Tendinitis, or inflammation of these tendons, often leads to pain that is worse at night because the horizontal position can stretch or compress the damaged tissue. The pain is often sharpest when lying on that side or when the arm is positioned awkwardly.
Another common culprit is subacromial bursitis, which is the inflammation of the bursa. When a person lies on the affected shoulder, the body’s weight directly compresses the inflamed bursa. This compression reduces the already limited space for the bursa, making the inflammation much more noticeable than during the day.
Shoulder impingement syndrome occurs when the rotator cuff tendons are pinched between the bones of the shoulder joint. At night, certain sleeping positions can re-create this pinching mechanism, especially if the arm is internally rotated or brought across the body. The continuous pressure on the compressed tendons and bursa results in a persistent, throbbing discomfort that interrupts sleep.
Adhesive capsulitis, commonly known as frozen shoulder, also causes nocturnal pain, particularly in its early, painful stage. This condition involves the stiffening and inflammation of the joint capsule. The pain is often described as deep and aching, and finding a comfortable position is difficult because any slight movement or strain on the stiff capsule causes pain.
Adjustments for Better Sleep and Relief
Sleeping Position Adjustments
Adjusting your sleeping posture is one of the most effective ways to reduce nocturnal shoulder pain. The best position is generally sleeping on your back, as this avoids placing direct pressure on either shoulder. If sleeping on your back, place a small pillow or rolled towel underneath the elbow of the painful arm to slightly elevate the joint and prevent the shoulder from rolling inward.
If you are a side sleeper, sleep only on the unaffected side. To protect the painful shoulder, hug a pillow to your chest and rest the affected arm on top of it. This maneuver prevents the shoulder from collapsing forward and keeps the joint in a more neutral, open position.
Pain and Stiffness Management
Several strategies can help manage pain before sleep:
- Applying a cold pack to the shoulder for 15 to 20 minutes before bedtime can help reduce inflammation and dull pain signals. Alternatively, a moist heat pack can relax surrounding tight musculature.
- Non-prescription anti-inflammatory medications, such as ibuprofen or naproxen, can be timed to reach peak effectiveness during the night’s most painful hours.
- Gentle, non-strenuous range-of-motion exercises, such as simple pendulum exercises, can be performed before bed to reduce stiffness and maintain mobility.
- Building a “pillow fort” around you can physically prevent you from rolling onto the painful side during the deeper stages of sleep.
When Professional Medical Help is Necessary
While home remedies and positional changes can offer relief, persistent shoulder pain warrants a professional medical evaluation. You should schedule a consultation if the pain lasts for more than a week or two without improvement, or if it continuously wakes you up multiple times a night. Pain that prevents you from completing simple daily activities, such as dressing or reaching for objects, also signals that medical intervention is needed.
Immediate medical attention is necessary if the pain results from an acute trauma, such as a fall, or if you experience sudden, significant weakness in the arm. The presence of neurological symptoms, including numbness, tingling, or a burning sensation that radiates down the arm, may indicate nerve involvement and requires prompt assessment.
Professional treatments aim to address the root cause of the pain and restore full function. These may include:
- Prescription anti-inflammatory medication.
- Targeted physical therapy to strengthen and stabilize the joint.
- Corticosteroid injections to decrease localized inflammation.
- Surgical consultation if non-surgical options fail to provide relief.