From what i have learnt the most important treatments for tendinopathy are strengthening (mainly eccentric) and stretching. Rest and ice are not beneficial. Rest is thought to contribute to the problem as the problem is one of degeneration of the tendon. Tendons respond to load by increasing the collagen production, immediately after exercise collagen production is at its lowest which can explain why tendinopathy is considered a chronic overuse injury (not giving time to allow the collagen production). However as time goes the collagen formation increases and reaches its peak at 4 days after the exercise (although strengthening should be done every 2nd day). Rest will not stimulate this response and the degeneration will slowly continue to occur.
Therefore we can conclude that to restore collagen in the tendon it is important to load the tendon, obviously high load exercises would be used very late in the treatment so initially strengthening using weights is prescribed as they exert a low load on the tendon. As the treatment goes on high load exercises such as running etc can be incorporated but make sure it is alternated along with the strengthening.
In terms of the strengthening; eccentric strengthening is considered much better as it is thought to have an effect on reducing the vascularisation that occurs with tendinopathy but it is important to eventually get to strengthening functionally as it is the eccentric to concentric turnaround which places the most strain on tendons. Pain is not a bad thing while strengthening, a study was done in which eccentric strengthening was done and the patients had to work through the pain and 90% improved.
Imaging such as ultrasound is considered unreliable as there can appear to be pathology but the patient has no pain and there can be pain but there does not appear to be any pathology on the imaging.