Muscle tone, the amount of resistance or tension in a muscle, is controlled by signals from the brain. When the brain areas responsible for sending out these signals become damaged from a stroke, changes in muscle tone occur from either an overactivity or underactivity of electrical signals to the muscles. This results in spasticity, where the muscles become overly stiff and tight, or flaccidity, where the muscles become weak and floppy. During stroke rehabilitation, many patients often encounter shoulder complications as a result of these changes in muscle tone.

4 Common Causes of Post-Stroke Shoulder Pain

• Shoulder Subluxation
• Shoulder Impingement
• Spasticity
• Frozen Shoulder

Shoulder Subluxation

Overview

With muscle flaccidity, the rotator cuff muscles that support and stabilize the shoulder joint become weak and underactive. As a result, the ligaments and joint capsule of the shoulder endure increased demands as they try to hold the upper arm in place in the shoulder socket. In the absence of activation from the rotator cuff musculature to hold the arm in place, movements of the arm out to the side or overhead in front of the body place additional stress on the stability of the shoulder joint and can cause subluxation, or partial dislocation. The continual pull of gravity on the weight of the arm causes further subluxation of the shoulder joint when the shoulder muscles are weak, resulting in pain over time.

Symptoms

• Shoulder pain
• Swelling
• Weakness and difficulty moving the arm
• Shoulder instability
• Numbness or tingling
• Visible malalignment of the shoulder joint

Treatment

• Proper positioning with a pillow or table tray under the arm when sitting
• Wearing a shoulder sling to support the arm when standing
• Electrical stimulation to improve activation of the rotator cuff muscles
• Exercises for shoulder strengthening

Shoulder Impingement

Overview

Increased friction and compression in the shoulder joint also occur from muscle flaccidity when the muscles of the back and shoulder do not work together in synchronicity. With overhead movements of the arm, the shoulder blades must rotate upward in order to allow enough space in the shoulder joint for the arm to elevate. When the muscles of the shoulder and back become flaccid and weak following a stroke, the scapula, or shoulder blade, cannot properly rotate upward when the arm is lifted, causing compression and pinching of the tendons that run through the narrow passageway of the shoulder. This is referred to as shoulder impingement and can make movements of the arm up overhead, out to the side, and behind the back painful, thereby limiting ease and independence with performing everyday activities.

Symptoms

• Shoulder pain, particularly with movement of the arm
• Pinching sensation at the top of the shoulder
• Increased pain with movements of the arm overhead, out to the side, or behind the back
• Decreased shoulder strength and range of motion
• Difficulty performing activities of daily living

Treatment

• Activity modification to allow rest and decrease irritation
• Medications to decrease pain and inflammation
• Strengthening exercises to restore proper muscle activation
• Joint mobilization to the shoulder and scapula to restore proper mobility

Spasticity

Overview

Alternatively, with muscle spasticity, increased muscle tone can tighten the shoulder muscles, causing muscle contractures that are stiff and painful. Spasticity of the shoulder significantly limits mobility and range of motion, making movements that involve the hand and arm challenging and pain-provoking.

Symptoms

• Pain in spastic muscles
• Tightness and stiffness
• Presence of contractures
• Significantly limited shoulder and arm range of motion

Treatment

• Medications to reduce pain
• Intramuscular injection of botulinum toxin (Botox to decrease spasticity
• Stretching
• Soft tissue mobilization
• Splinting and serial-casting to increase muscle length

Frozen Shoulder

Overview

Due to decreased movement of the arm and shoulder joint from spasticity, the ligaments and joint capsule of the shoulder can also stiffen. This can develop into adhesive capsulitis, commonly referred to as “frozen shoulder,” where the connective tissue in the shoulder joint thickens and tightens, limiting range of motion and causing pain with arm movements. Frozen shoulder is classified into three stages:

1. Freezing stage: the shoulder joint begins to lose range of motion and movements of the arm become painful
2. Frozen stage: the shoulder becomes stiffer with a significant loss of range of motion and pain may continue or begin to decrease
3. Thawing stage: range of motion begins to improve as pain continues to decrease

Symptoms

• Shoulder pain
• Stiffness and difficulty moving the arm
• Difficulty sleeping
• Significant limitations in shoulder range of motion, especially shoulder flexion, abduction, and external rotation

Treatment

• Corticosteroid injection to the shoulder to reduce inflammation
• Medications to reduce pain and inflammation
• Stretching and shoulder range of motion exercises
• Joint mobilization to the shoulder to restore mobility
• Strengthening exercises to restore proper muscle activation

If You Are Experiencing Shoulder Pain Post-Stroke

Early treatment is crucial for optimal stroke rehabilitation. If left untreated, shoulder complications can worsen substantially and make everyday tasks and movements of the arm very challenging. If shoulder symptoms such as pain and difficulty with arm movements are present, stroke survivors should seek the care of a medical doctor and physical therapist as soon as possible to initiate a plan of care to optimize recovery, decrease pain, improve normal muscle tone, and increase strength and range of motion.

Stroke survivors and supporting family members and caregivers should be mindful of shoulder protection strategies to assist in recovery. Proper positioning to support the arm and shoulder when seated or lying down can help improve joint alignment, and the use of an arm sling when standing can minimize strain of the arm on the shoulder. When assisting a stroke survivor with tasks such as getting in and out of bed, standing up, and walking, family members and caregivers should not pull from or hold onto the affected arm or shoulder to prevent the possibility of a ligament sprain, muscle strain or tear, or shoulder dislocation due to the decreased integrity and stability of the shoulder post-stroke.

References

O’Sullivan, S. B., Schmitz, T. S., & Fulk, G. D. (2014). Physical rehabilitation (6th ed.). Philadelphia: F.A. Davis Company.

Yelnik, A. P., Colle, F. M., Bonan, I. V., & Vicaut, E. (2007). Treatment of shoulder pain in spastic hemiplegia by reducing spasticity of the subscapular muscle: a randomised, double blind, placebo controlled study of botulinum toxin A. J Neurol Neurosurg Psychiatry, 78(8), 845-848. doi: 10.1136/jnnp.2006.103341

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