What is Quadrilateral Space Syndrome (QSS)?

Quadrilateral Space Syndrome (QSS) is a rare condition that occurs when the axillary nerve and/or the posterior circumflex humeral artery get squeezed or compressed as they pass through a small area in the back of your shoulder called the 'quadrilateral space.' This compression can lead to pain, numbness, tingling, and weakness in your arm.

QSS is often caused by repetitive overhead activities, common in athletes like throwers, swimmers, and tennis players. It can also result from repeated motions that narrow the space (overuse), extra bands of tissue that can form and compress the nerve or artery (fibrous bands), trauma or injury such as a shoulder dislocation or a direct blow to the shoulder which can cause swelling or scar tissue, or muscle enlargement if muscles in the area grow significantly (e.g., in bodybuilders), they can crowd the space.

What are the common symptoms of QSS?

Symptoms typically include vague pain or a dull ache in the back of the shoulder, sometimes radiating down the arm; numbness, tingling, or a 'pins and needles' sensation in the shoulder and upper arm; pain that worsens with overhead movements or when your arm is in a 'throwing' position; tenderness when pressure is applied over the back of the shoulder in the quadrilateral space; weakness or fatigue in the arm, especially when lifting or rotating it; and sometimes, shrinking (atrophy) of certain shoulder muscles like the teres minor or deltoid.

How is QSS diagnosed?

Diagnosing QSS can be challenging because its symptoms can be similar to other shoulder problems. Your doctor will ask about your symptoms, activities, and any past injuries; perform a physical examination to check your shoulder's range of motion, strength, sensation, and tenderness; may order imaging tests like MRI or ultrasound to look at the quadrilateral space, assess muscle size, and check for any abnormalities or scarring. In some cases, nerve conduction studies (NCS) or electromyography (EMG) might be performed to evaluate how well the axillary nerve is working. An injection of local anesthetic into the quadrilateral space that temporarily relieves your symptoms can also help confirm the diagnosis.

What are the non-surgical treatment options?

Most cases of QSS improve with non-surgical treatment. These options focus on reducing pressure on the nerve and artery, managing pain, and restoring function: rest and activity modification (avoiding or modifying activities that worsen your symptoms, especially overhead movements); anti-inflammatory medications (over-the-counter or prescription NSAIDs like ibuprofen can help reduce pain and inflammation); ice or heat packs (applying ice can help reduce pain and inflammation, especially after activity, heat can help relax muscles); physical therapy (a physical therapist will guide you through exercises to maintain or improve shoulder range of motion and flexibility, strengthen the muscles around your shoulder to provide better support, improve posture and body mechanics); and corticosteroid injections (in some cases, your doctor may suggest an injection of corticosteroid medication into the area to reduce inflammation and pain).

When is surgery considered for QSS?

Surgery is usually considered if non-surgical treatments haven't significantly improved your symptoms after about six weeks or more; symptoms are severe or progressively worsening; or there's clear evidence of nerve damage or significant compression.

What does the surgical procedure involve?

The goal of surgery, called decompression, is to relieve pressure on the axillary nerve and posterior circumflex humeral artery. This typically involves making a small incision at the back of your shoulder; identifying the compressed nerve and artery; carefully removing or cutting any fibrous bands, scar tissue, or other abnormal structures that are causing the compression. The procedure is designed to free up the nerve and artery, allowing them to function normally.

What are the potential risks of surgery?

As with any surgery, there are potential risks, though QSS surgery is generally safe. These can include infection, bleeding, damage to surrounding nerves or blood vessels, scarring, persistent pain or incomplete relief of symptoms, and reaction to anesthesia. Your surgeon will discuss these risks with you in detail.

What do I need to do before surgery?

Your healthcare team will provide specific instructions, but generally, you may need to undergo a pre-operative physical examination and blood tests; stop certain medications (e.g., blood thinners, some anti-inflammatory drugs) a week or two before surgery; arrange for someone to drive you home after surgery and help you during the first few days of recovery; and avoid eating or drinking for a certain period before the surgery.

What can I expect immediately after surgery?

You will likely have your arm in a sling to help it rest and heal. You may experience some pain, which will be managed with medication. Your surgical site will be covered with a dressing. Your surgeon will give you instructions on wound care and activity restrictions.

How long is the typical recovery period?

Recovery times vary for each person, depending on the severity of the condition and how long the nerve was compressed. First few weeks (0-2 weeks): Focus on rest, pain management, and protecting the surgical site. Gentle elbow and wrist movements will be encouraged. Weeks 2-6: You will start physical therapy, focusing on gentle range-of-motion exercises for your shoulder. After 6 weeks: As healing progresses, your physical therapist will introduce strengthening exercises to rebuild muscle strength. Overall, it can take several weeks to months to feel significant improvement, as nerve healing is a slow process.

What does rehabilitation/physical therapy involve?

Physical therapy is crucial for a successful recovery. Your therapist will design a personalized program that may include pain and swelling management (using ice, gentle massage, or other techniques); range of motion exercises (to restore full movement in your shoulder); strengthening exercises (targeting the muscles around your shoulder, including the deltoid and teres minor, which may have been weakened); postural correction (to improve overall shoulder mechanics); and activity-specific training (gradually reintroducing movements related to your work, sports, or daily activities).

How will pain be managed?

Your doctor will prescribe pain medication to help manage discomfort after surgery. This may include prescription pain relievers (e.g., opioids for a short period); over-the-counter pain relievers (e.g., acetaminophen, ibuprofen) as recommended by your doctor. You may also use ice packs to reduce localized pain and swelling.

When can I expect to return to daily activities, work, driving, and sports?

This timeline varies greatly based on your recovery progress and the demands of your activities. Daily activities: Light daily activities can usually be resumed within a few days to weeks. Driving: You can typically drive once you are no longer taking strong pain medications and have sufficient control and range of motion in your shoulder to safely operate a vehicle (often a few weeks after surgery). Work: Return to work depends on the nature of your job. Light, desk-based work might be possible within a few weeks, while jobs requiring heavy lifting or repetitive overhead movements will take longer, potentially several months. Sports: A gradual return to sports, especially overhead activities, will be guided by your physical therapist and surgeon, often not for several months after surgery. Full return to competitive sports may take 3-6 months or longer.

What is the expected long-term outcome?

For many patients, surgical decompression of QSS provides significant relief from pain, numbness, and weakness, allowing them to return to their normal activities, including sports. Nerve healing can be slow, so improvement may continue for several months. While some mild symptoms may occasionally linger, the goal is to significantly improve your quality of life and shoulder function.

Non-Operative Exercises

Eccentric Loading Protocols Exercises

Step-by-step home exercise guide for Eccentric Loading Protocols to improve mobility, strength, and recovery.

Active rehabilitation is a cornerstone of recovery. On this page, we outline key home exercises for Eccentric Loading Protocols designed to help you regain shoulder function. Always consult your care team before beginning.

Active rehabilitation is the cornerstone of tendon recovery. Eccentric loading—the phase of exercise where a muscle and tendon are lengthened under load—is one of the most effective non-operative protocols for restoring shoulder tendon health. By focusing on slow, controlled lowering movements, you can stimulate collagen production, improve tendon strength, and promote optimal tissue remodeling. This guide outlines a structured, safe home program to help your shoulder rebuild strength and recover from tendinopathy.

General Guidelines & Safety Precautions

Warm-Up: Begin with 5 minutes of gentle movement, such as shoulder shrugs, light arm circles, or applying moist heat, to increase blood flow before exercising.
The Pain Rule: It is normal to feel a mild, dull ache or therapeutic strain (up to a 3 out of 10 on a pain scale) during eccentric exercises. However, if you experience sharp, stabbing pain, or if pain increases significantly after a session, stop immediately.
Control is Key: The magic of eccentric loading happens during the lowering phase. Never rush or let your arm snap back. Use your healthy arm to lift the weight or band, then let the affected arm do the work of lowering it slowly.

Exercise 1: Eccentric Shoulder External Rotation

Purpose: Focuses on loading the infraspinatus and teres minor tendons to build load tolerance and stimulate collagen remodeling on the back of the shoulder.

Equipment Needed: A light resistance band anchored at elbow height.

Starting Position: Stand tall with feet shoulder-width apart. Hold the band with the affected hand, elbow bent at 90 degrees and tucked close to your side. Place a small rolled towel between your elbow and rib cage.

Instructions:

Use your unaffected hand to help rotate the affected arm outward away from your stomach.
Once rotated outward, release the assisting hand so only your affected arm holds the resistance.
Slowly, over a count of 5 seconds, rotate your arm back inward to the starting position.

Dosage: 3 sets of 10 repetitions, once daily.

Form Tip: Ensure your elbow remains pinned against the towel throughout the exercise. Do not let the arm snap back.

Exercise 2: Eccentric Supraspinatus Scaption Lowering

Purpose: Specifically targets the supraspinatus tendon at the top of the shoulder joint, strengthening it in its natural line of pull.

Equipment Needed: A light weight (1-3 lbs dumbbell or a small water bottle).

Starting Position: Stand with feet hip-width apart and shoulders relaxed, holding the weight in your affected hand.

Instructions:

Use your opposite (healthy) hand to lift your affected arm up to shoulder height, angled slightly forward (about 30 degrees, in the plane of the shoulder blade).
Once at the top, release your healthy hand.
Slowly lower the affected arm back down to your side, taking a full 5 to 6 seconds to complete the descent.

Dosage: 3 sets of 10 repetitions, once daily.

Form Tip: Keep your thumb pointing slightly upward. Avoid shrugging your shoulder toward your ear during the lowering phase.

Exercise 3: Eccentric Shoulder Flexion (Frontal Lowering)

Purpose: Loads the anterior deltoid and the long head of the biceps tendon at the front of the shoulder.

Equipment Needed: A light weight (1-3 lbs).

Starting Position: Stand upright with your arm at your side, holding the weight.

Instructions:

Using your healthy arm for assistance, lift the affected arm straight forward until it reaches shoulder height.
Remove the assisting arm.
Slowly lower the affected arm straight down to your side over a count of 5 seconds.

Dosage: 3 sets of 10 repetitions, once daily.

Form Tip: Keep your core engaged and your posture upright. Do not lean backward or sway your torso to control the weight.

Exercise 4: Eccentric Internal Rotation

Purpose: Targets the subscapularis tendon on the front of the shoulder, helping to stabilize the front of the joint.

Equipment Needed: A resistance band anchored at elbow height.

Starting Position: Stand sideways to the band anchor. Hold the band with the affected hand (closest to the anchor), elbow bent at 90 degrees and kept close to your side.

Instructions:

Use your unaffected hand to pull the band across your stomach, rotating your affected arm inward.
Remove the assisting hand.
Slowly, over a count of 5 seconds, let the band pull your affected hand back outward toward the anchor point.

Dosage: 3 sets of 10 repetitions, once daily.

Form Tip: Keep your torso facing forward. Do not twist your body to pull the band or to resist it.

Always consult with your physical therapist or doctor before starting a new exercise routine. If any exercise causes persistent pain or swelling, discontinue it and contact your healthcare provider.

Disclaimer: This guide provides general exercise instructions and is not a substitute for professional medical advice. Always consult your doctor or qualified healthcare provider with any questions you may have regarding your specific medical condition and treatment plan.

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