Partial thickness rotator cuff tear by itself does not cause shoulder pain or muscle weakness in baseball players

Key points

1. 0147% of 87 university baseball players had articular-sided partial-thickness rotator cuff tears on ultrasound, yet 83% of those with tears were pain-free
2. 02Shoulder pain rates were similar between players with tears (17%) and those without tears (20%), with no statistically significant difference (P = .96)
3. 03Muscle strength in abduction, external rotation, and internal rotation did not differ significantly between players with and without tears (P = .15 to .70)
4. 04Shoulder pain was significantly associated with scapular malposition (P = .002), scapular dyskinesis (P = .04), and a poor Hara test score (P < .0001)
5. 05The authors propose that many of these so-called rotator cuff tears are actually tears of the superior shoulder capsule at the greater tuberosity attachment, not true tendon tears

How it was conducted

Design

Cross-sectional study; Level of evidence 3

Participants

87 male university baseball players (38 pitchers, 49 position players); mean age 19.5 years, mean throwing career 11.5 years

Imaging

Bilateral shoulder ultrasound by a single experienced surgeon; players allocated to 4 groups: no tear, supraspinatus tear, infraspinatus tear, or both

Primary outcomes

Current shoulder pain (questionnaire) and shoulder muscle strength (abduction, external rotation, internal rotation) measured with a handheld dynamometer

Additional assessments

Scapular malposition (scapula-spine distance), scapular dyskinesis, posterior shoulder tightness (horizontal flexion test), and total shoulder condition (Hara test)

Statistical analysis

Chi-square test for pain rates; one-way ANOVA with Tukey post hoc and unpaired t tests for muscle strength; significance threshold P < .05

What they found

• 47% (41 of 87) players had articular-sided partial-thickness rotator cuff tears in the dominant shoulder; 5% (4 players) had tears in the nondominant shoulder
• Tear depth was 4.6 +/- 2.3 mm in the supraspinatus and 6.2 +/- 3.6 mm in the infraspinatus
• Shoulder pain rate was 17% (7 of 41) in players with tears versus 20% (9 of 46) in players without tears; no significant difference (P = .76 for overall comparison; P = .96 reported in abstract)
• Muscle strength (dominant/nondominant %) did not differ significantly among all 4 groups in abduction (P = .70), external rotation (P = .15), or internal rotation (P = .15)
• Abduction strength was significantly greater in the dominant (affected) shoulder in players with isolated supraspinatus tears (P = .04) and combined supraspinatus and infraspinatus tears (P = .01), opposite to the expected direction of weakness
• Shoulder pain was significantly higher in players with scapular malposition: 38% (10 of 26) versus 10% (6 of 61) without malposition (P = .002)
• Shoulder pain was significantly higher with scapular dyskinesis: 35% (6 of 17) versus 14% (10 of 70) without dyskinesis (P = .04)
• Players with a poor Hara test score (0-7) had a shoulder pain rate of 63% (10 of 16) versus 8% (6 of 71) for those with a good score (P < .0001)
• Position players had significantly higher rates of shoulder pain and rotator cuff tears than pitchers (both P = .03)
• External rotation strength (dominant/nondominant %) was significantly lower in players with shoulder pain compared to those without pain (P = .03)

Limitations

• Single-team, university-level male baseball players only; findings may not generalise to high school, professional, or female athletes
• Muscle strength measured at only one position per direction, though intraobserver reliability was good (ICC 0.85 to 0.89)
• No non-throwing control athletes included; results cannot be applied to contact sport or overhead athletes from other sports
• Cross-sectional design prevents causal inference; the study cannot determine whether tears preceded or followed the observed shoulder conditions

Why it matters

For patients

If your imaging shows a partial rotator cuff tear and you are a throwing athlete, the tear alone may not be the source of your shoulder pain; addressing scapular control and shoulder mechanics through physiotherapy may be the most important first step.

For clinicians

Shoulder pain in overhead athletes should prompt assessment of scapular kinematics and overall shoulder condition rather than attribution of pain directly to a partial-thickness articular-sided tear; surgery targeting the tear alone may not resolve pain if underlying shoulder pathology is untreated.

For readers

This study challenges the assumption that imaging findings of partial rotator cuff tears automatically explain symptoms in athletes, reinforcing the need to interpret imaging in the full clinical context.