Currently, there is little information on the clinical, radiographic and electric profile of patients younger than 65 years of age with large rotator cuff tear. According to our hypothesis, massive rotator cuff tear, when discovered after recent traumatism, do not provide typical radiographic findings and suprascapular nerve impairment in large rotator cuff tears is uncommon. This is a prospective, descriptive, multicenter study of a series of 112 patients younger than 65 years, including 66 males and 46 females with extensive or massive cuff tear. Duration of symptoms was less than 6 months in 28 cases and secondary to trauma in 57 cases. Patients had loss of elevation or external rotation or both in 57 cases. An electromyogram (EMG) of suprascapular nerve was performed in 50 cases. A higher incidence of advanced fatty infiltration of the infraspinatus muscle (>stage 2 according to Goutallier) was observed in case of long-term symptomatology or in the absence of known trauma. Traumatic status was commonly found in patients with functional deficit in shoulder elevation, thus reporting a significantly lower Constant score (p<0.0001). Patients with both loss of shoulder elevation and external rotation had a significantly narrower subacromial space (5mm versus 7.2mm). No significant relationship could be established between electric impairment and massive cuff tear. According to the present study, in case of traumatic context and recent symptomatology, subacromial height and fatty infiltration of the infraspinatus muscle are better prognostic factors despite a pseudoparalytic shoulder. Repair should thus be considered. Moreover, the interest of a preoperative suprascapular nerve EMG is questionable.