What could cause trapezius and shoulder pain with stiffness after hearing a pop during an overhead weight workout two weeks ago, despite preserved range of motion and strength?

Trapezius and Shoulder Pain After Overhead Weight Training

You most likely have a partial-thickness rotator cuff tear with associated trapezius muscle dysfunction and possible scapular dyskinesis, given the acute "pop" during overhead lifting, persistent pain and stiffness at two weeks, but preserved strength and range of motion.

Most Probable Diagnosis

The clinical presentation strongly suggests rotator cuff tendinopathy or partial-thickness tear with secondary trapezius muscle involvement 1, 2. The audible "pop" during overhead weight training is a classic indicator of acute soft tissue injury, and the two-week timeline with persistent symptoms but maintained function is characteristic of partial rather than full-thickness tears 1.

Key Diagnostic Features Supporting This:

• Preserved strength and ROM: Full-thickness rotator cuff tears typically present with weakness and limited active range of motion, whereas partial tears often maintain these functions 2
• Trapezius stiffness: Overhead athletes with rotator cuff pathology demonstrate significantly increased upper trapezius muscle stiffness (measured by shear modulus) compared to asymptomatic athletes 3
• Muscle imbalance pattern: The trapezius dysfunction you're experiencing reflects the documented imbalance where upper trapezius activity increases while middle and lower trapezius activity decreases in rotator cuff injuries 4

Underlying Mechanism

The "pop" likely represented either:

• Partial rotator cuff fiber disruption (most common with overhead loading) 1
• Acute tendinopathy with inflammatory response 3
• Scapular stabilizer strain leading to altered scapulohumeral rhythm 5

The persistent trapezius stiffness is a compensatory response where the upper trapezius overworks to stabilize the scapula when rotator cuff function is compromised 3, 4. This creates a vicious cycle of muscle imbalance and continued pain 5.

Recommended Diagnostic Approach

Initial imaging should be plain radiographs of the shoulder to rule out fracture or dislocation, as this is the appropriate first step for acute shoulder pain 1.

If radiographs are normal or nonspecific (which is likely given your preserved ROM and strength), the next step is MRI shoulder without IV contrast, which is the gold standard for evaluating rotator cuff pathology 1. MRI has high sensitivity and specificity for full-thickness tears but lower sensitivity for partial-thickness tears compared to MR arthrography 1. However, in your acute post-traumatic setting with likely joint effusion, standard MRI without contrast should provide adequate soft tissue visualization 1.

Alternative Imaging Consideration:

Ultrasound has 90-91% sensitivity and 93-95% specificity for full-thickness rotator cuff tears, similar to MRI 1. However, its performance for partial-thickness tears is more variable and operator-dependent 1. Given the clinical suspicion for partial tear, MRI is preferred 1.

Management Strategy

Conservative Treatment (First-Line):

Since you have a chronic, symptomatic presentation (two weeks duration) with preserved function, conservative management is appropriate initially 2:

• Pain control: NSAIDs and activity modification 2
• Physical therapy focus: Restoration of scapular muscle balance is critical 4, 5. The rehabilitation must address:
  • Reducing upper trapezius overactivity 3, 4
  • Strengthening middle and lower trapezius 4
  • Correcting scapular dyskinesis patterns 5

Regarding Corticosteroid Injections:

The evidence is inconclusive for subacromial corticosteroid injections in rotator cuff tears—one level II study showed no significant benefit over lidocaine alone at 6 weeks, though level IV studies suggest short-term improvement 2. Given the equivocal evidence and theoretical concerns about tendon healing, this should be a shared decision if conservative measures fail 2.

Surgical Consideration:

Rotator cuff repair is an option for chronic, symptomatic full-thickness tears 2. However, given your preserved strength and ROM, you likely have a partial tear that warrants a trial of conservative management first 2. Surgery becomes more relevant if symptoms persist beyond 3-6 months of appropriate rehabilitation or if there is functional deterioration 2.

Critical Pitfalls to Avoid

• Don't ignore the scapular component: Focusing only on rotator cuff rehabilitation without addressing trapezius imbalance and scapular dyskinesis will lead to persistent symptoms 4, 5
• Overhead work exacerbates the problem: Studies show overhead activities significantly decrease pressure-pain threshold in the upper trapezius and reduce cervical ROM 6. You must modify your training to avoid overhead loading during the acute recovery phase
• Preserved ROM doesn't rule out significant pathology: Partial-thickness tears can maintain full ROM and strength while still causing substantial pain and dysfunction 1, 2

Expected Timeline

With appropriate conservative management focusing on scapular rehabilitation, most partial rotator cuff injuries improve over 6-12 weeks 2. The trapezius stiffness should resolve as the underlying rotator cuff pathology improves and muscle balance is restored 3, 4.