Tendinopathy is usually diagnosed on your presenting history and clinical examination.
Different areas of the body might have subtle nuances in terms of presentation and physical tests, but for most tendinopathies, an ultrasound examination is very helpful when supporting the history and examination findings. Most MSK or Sports Physicians should be able to do this for you and depending on the finding, they will advise on you the apropriate course of action.
In chronic tendinopathy, there can be swelling, stiffness and redness around the tendon. It is important to get this looked into, as over time, tearing within the tendon can occur.
Hope this helps.