When reading the research they commonly use 2 terms tendinosis and tendinopathy so I've defined below to prevent confusion as tbh i though they were the same but they aren't:
is a broad term encompassing painful conditions occurring in and around tendons in response to overuse.
Degenerative changes to the tendon cell and tendon matrix that have no pain.
There are 3 stages of tendinopathy:
All of these sit on a continuum where you go through flare ups and remission. You can essentially regain full recovery from a reactive and dysrepair tendon but for a degenerative tendon the patient will always have to manage an element of discomfort and manage flare ups more regularly. There's a chart below which takes you through these 3 stages and there continuum:
Lower limb tendons are load bearing where as upper limb are positional tendons.
Mid portion tendonopathies do well with a gradual loading programme, enthesiopathies (insertional tendons) respond well to the same but avoid end range loading until mid way through the programme and avoid tendon compression on initial stages of rehab.
Achilles respond well to gradual loading of bilateral leg concentric-eccentric and progress to single leg not forgetting the soleus (bent knee loading) as the soleus forms the higher proportion in the achilles tendon and then progress to heavy strength followed by plyometrics/stretch shorten cycle. A good programme that is used by the tendon gurus is the Silbernagel Programme (P. Malliaras, K.G. Sibernagel, S. Oneil). The important part to remember is your patients function level and what they are aiming to get back to. Seth O'Neil looked at runners and achilles tendinopathy and found that individuals with pathological tendons have a bilateral weakness.
Patella tendonopathy respond well to HSR decline squat (15-20 degrees) (M. Konsguaard, J. Cook, J.E. Gaida, A. Rudavsky) but not in the initial stages and looking at loads of 70% of 1RM. Below is the link to for the set programme and exercises for the Patella rehab:
Gluteal tendinopathies (A. Grimaldi) respond well to gradual loading programme but looking at loads of 20-30% of 1RM and you rehab this like an upper limb tendonopathy based on the research.
Difference between upper limb and lower limb tendons is the load you put the tendon through. However given the research regarding gluteal tendonopathy it may be due to levers and pivot points (In that longer levers require gentler loading).
Upper limb research looks more into the symptoms being centrally driven (C. Littlewood, J.Brox) and strengthening research is very limited in this area but its slow and gradual loading looking at isolating the tendon (eg. infraspinatus, lateral or medial rotation) and then moving onto shoulder joint and girdle movement (horizontal abduction) and closed chain exercises progressing up to high speed strengthening (J.Brox), not forgetting the kinetic chain, looking at stabilising the trunk to enhance the stability of the movement (J. Gibson).
Pain doesn't necessarily related to the pathology of the tendon (Il refer you to 2 great articles called: 1) The Pain of Tendinopathy: Physiological or Pathophysiological by E. Rio, L. Moseley, C. Purdam, T. Samirie, D. Kidgell, A. Pearce, S.Jaberzadeh, J. Cook, 2014 . 2) Is tendon Pathology a continuum? A pathology model to explain the clinical presentation of load induced tendinopathy, by J. Cook, C. Purdam. 2008).
You can prevent reoccurrence of tendinopathy by carrying out heavy strength training 2x week. (K.G. Silbernagel, A. Brorsson, M. Lundberg 2011, The majority of patients with Achilles tendinopathy recover fully when treated with exercise alone: a 5-year follow-up)
Overall they all (Regardless of where they are) respond well to gradual loading programme over a 6-12 week period starting at isometric (to help with pain management) to isotonic (concentric-eccentric) then strength training (slow speed and then high speed) and finally plyometrics. Don't forget with the upper limb to incorporate closed chain as this helps with muscle activation and open chain for the lower limb.
The research in this area is generally limited so you gotta take what you can get but theres enough to guide you.
Hope that helps