Tendonitis means it is an injury to the tendon with inflammation cells present, and Tendonosis is an injury to the tendon without inflammation cells being present...You do not need to have inflammation first, and injury can start as Tendonosis...
In chronic tendonitis, tendon becomes scared, thickened, less elastic, harder to slide in sheath, sometimes with limited ROM...
There is also Tenosynovitis which is inflammation of the synovial sheath or covering of a tendon...
There is also the danger of Calcific Tendonitis where a calcium growth will occur within the tendon, or in other words a small bone fragment could form within the tendon.
Like previously mentioned...You can treat tendonitis/osis/synovitis with increasing ROM through stretching, increasing tissue extensibility via Myofascial Release. Cross Friction massage is nice because it is used to "restart" the healing process by kind of damaging you in a minor way... Ultrasound treatment is used in a clinical setting in combination with massage and stretching to increase tissue extensibility, increase ROM, and to decrease fascial adhesions.
I would also recommend the use of an NSAID such as Ibuprofen if not contraindicated medically. I would recommend the use of it for a 2 week stint, taking it 2-3 times a day. You need the constant exposure in your bloodstream for a prolonged length of time for it to do it's job.
The last piece of advice is probably the most common...Ice...Ice Ice Ice...The physiological affects of ice are very beneficial. For patellar tendonitis you could try and use Ice Cup Massage over the tendon
.....If using a commercial gel pack from a freezer, cover it with a wet damp cloth...Not a bath towel, but a dish towel style cloth. If you are using ice cubes or crushed ice, then apply the ice directly to the skin for 20-30 minutes with compression if not contraindicated by cold allergies or peripheral vascular disease...
Brought to you by a soon to be Certified Athletic Trainer