###### Abstract  
Different levels of pain, with various symptoms, are present in patients with rotator cuff tears. The purpose of this study was to evaluate the expression of factors related to pain on the long head of the biceps tendon (LHBT) and structures adjacent to the LHBT in patients with supraspinatus tears and to compare the differences in order to verify whether the structures are affected by the condition of the LHBT. Forty patients who underwent arthroscopic supraspinatus repair were enrolled. Patients with an intact LHBT were allocated to group 1 and patients with pathologic LHBTs were allocated to group 2. With the acquisition of tissues from the LHBT, anterior capsule, rotator interval, and subacromial bursa, the expressions of protein gene product 9.5 (PGP9.5), growth-associated protein 43 (GAP43), calcitonin gene-related peptide (CGRP), substance P, P75, S100, and CD34 were analyzed using real-time reverse transcription polymerase chain reaction and immunohistochemistry. The gene expression levels of PGP9.5 (\(p=0.02\)), GAP43 (\(p=0.03\)), CGRP (\(p=0.007\)), and CD34 (\(p=0.03\)) from the LHBT were significantly higher in group 2. PGP9.5 (\(p=0.04 Aside from the pain caused by the LHBT, the rate of concomitant stiffness is reported to be high when the LHBT is involved in a rotator cuff tear, due to continuous pain or contracture of the capsule that occurs gradually over time [7; 8; 9]. This fact clearly indicates that capsules and rotator intervals are under the influence of other pathologic conditions of the shoulder joint, and they contribute to the evocation of the shoulder joint. However, in the case of rotator cuff tears with stiffness, the recovery factors that enable immediate rotator cuff recovery or delayed recovery of the rotator cuff after the recovery of range of motion have not yet been determined when selecting the optimal treatment. Regarding the close geographical proximity of the rotator interval, joint capsule, and LHBT to the rotator cuff, there are chances that these structures are affected by one another and that may manifest in various symptoms and different levels of pain. In addition, the subacromial bursa, which is known to be one of the most common sources of shoulder pain, especially when it is involved with rotator cuff tendinopathy, may also be affected by the condition of the LHBT. If we are able to predict the potential pain source in the shoulder that is coexistent with a rotator cuff tear and LHBT pathology, indications for prophylactic or simultaneous treatment of the lesions can lead to optimal postoperative outcomes along with successful repair of the torn tendon.  
The purpose of this study was to elucidate whether adjacent anatomical structures including the anterior capsule, rotator interval, and subacromial bursa are affected by the condition of the LHBT in patients with rotator cuff tears by evaluating the expression of pain-related factors and comparing patients with and without LHBT lesions. These factors were also evaluated among LHBT tissues in order to verify LHBT itself as a pain source in pathologic conditions. The analyzed markers were deliberately chosen among the neuronal and pain-related peptides that have been proven to be involved in different aspects of the pain-generating mechanism with the confirmation of their presence in various bone and joint problems, including shoulder diseases.