Knee and shoulder pain can have various causes. Here are a few possible ones. Knee pain: 1. Sports injuries: such as sprains, ligament or cartilage tears, fractures, among others. 2. Joint wear and tear: osteoarthritis is one of the main causes of chronic pain in the knee, especially in older people. Bursitis: inflammation of the bursae (small fluid-filled sacs) that cushion the knee joint. Tendonitis: inflammation of the tendons in the knee, usually...