I’m a young medieval warrior (be it Viking, Knight, samurai or whatever) and I get a chronic or recurring injury (something like a rotator cuff or slap injury). It’s not immobilizing and even though it does hurt quite a bit, I’m a medieval warrior damn it, I can take it. But I realize that my strength isn’t the same. The pain does take its toll and my mobility isn’t the same. I’m not as good a wrestler, not as good a swimmer, and not as proficient in battle. All because of that one stupid injury. How is my life affected by this? Do my peers acknowledge my injury or am I considered weak? Do I keep on partaking in sports, battle training and actual war? Is this injury an excuse to stop fighting? Do I consider myself weak for having this incurable and insufferable pain, specially when there are people around me that have lost arms or legs in war and still try their best (yet don’t experience the same daily pain as I do)? How would that have been for a person back then?
I cannot answer for the samurai, but for the "Vikings" as well as "Knights" we have a pretty well documented knowledge.
You need to look no further than Bent Thordeman's work on the battle of Visby, or Lukasiewicz's work on the osteology of the Battle of Grunwald.
We can clearly guess from the found bones that men with serious injuries or chronic damage to their skeletons (worn out joints, severe scoliosis, osteoporosis, badly healed breaks etc) would heal, and go back to battle, despite what obviously would be a painful and handicapping injury.
One example from Visby, was, as far as I remember, a man who had bad knee joints, severely damaged hip joint (from a childhood injury), broken/cut ribs also badly healed (from a previous battle) , axe wound to the head and face that also healed improperly, and probably hurt a lot, and finally died at Visby at around 65 due to spear to the eye.
From numerous examples like this we can guess that people suffering from such an injury or disease would just go back to work, and participate in battle anyway, to the best of their ability. It is important to remember that personal fitness, strength and dexterity was less important in battle than sheer stamina and the ability to follow tactical orders, which does not exclude partially handicapped warriors.
One type of chronic disease that was largely exempt from it was gout (foot arthritis) and similar severe injuries to the leg that would make a person unable to walk, march and carry weight. But then again, gout and arthritis were diseases most likely to happen to older, and rich men (since the major contributor to gout is sedentary lifestyle, alcohol and fatty diet). Not exactly soldier material.