Shoulder muscles have a hard lump pain when moving may be due to muscle strain, arthritis, frozen shoulder and other reasons, the details are as follows: 1. Muscle strain: this is a long-term action or weight-bearing exercise, resulting in local muscle fiber damage, local muscle spasm, which will cause the shoulder muscle has a hard lump pain when moving symptoms. 2. Arthritis: when suffering from arthritis, it may make the local joint tissues loose, causing abnormal adhesion of muscle tissues, pulling the surrounding tissues, which will cause the symptom of pain in the shoulder muscles when there is a hard lump activity. 3. Frozen shoulder: when the shoulder muscles are cold or overworked, causing local muscle inflammation, when the inflammation stimulates the local shoulder muscles or nerve tissues, it may lead to the symptom of pain when moving the shoulder muscles with a hard lump. Caused by a hard shoulder muscle pain when moving more causes, also need to consider whether the shoulder bone tumor and fracture displacement and so on. The specific situation should also go to the hospital in time for examination and diagnosis, so as to carry out targeted treatment.