Hi, I study bio-mechanics and more specifically how different activities cause loading of soft tissue structures in the knee. What this means is that I look at how tension in the knee ligaments and tendons predisposes a person to knee injury.
Very commonly people with non specific knee pain without an observable origin (i.e. you don't have observable disrupted/torn ligament or tendon fibers, a degenerative cartilage surface, or bone fracture or osteoid growing in your articular space) are suffering from structural strain and impingement that predisposes the them for "blowouts" like acl/mcl tears in the future.
Your pain is real and is commonly caused by one or more of the following things most of the time: improper muscle compartment balance (i.e. your quads and hamstrings are unequally trained), poor neuromuscular control (your body does not smoothly activate the muscle groups sequentially), or you have preliminary inflammation that is effecting your neuromuscular control through guarding reflexes. This is all very fixable with PT, REST, modification of exercise programs and GENTLE USE OF ANTIINFLAMMATORIES. GENTLE because many of my hunting compatriots like to use ibuprofen, tylenol, and naproxen like skittles which can actually harm your ligaments and tendons while they try to heal not to mention the nasty effects on the stomach, kidneys, and liver.
The big thing I see in a lot of these posts is people over training and doing things that are causing a lot of load on their knees and other structures. They also tend to do them repetitively in a last hurrah trying to get ready for the season. They then expect their knees/back/ankles to feel great the day after. Your body is very tough and very good at healing but if you climb 100 flights of stairs with a 100 pounds on your back, do wind sprints with a rock over your head, and jump off your roof, every other day it just can't keep up. It is always a good idea to incorporate non load bearing cardio into your training to offset big days of rucking, running, or lifting; i really like cycling, rowing, and swimming because the work a lot of different muscles in my body that are applicable to hunting and rucking but they don't beat the **** out of my body. It may not hit the same as your normal running or lifting routine but that's not the pount of doing those exercises; the point is active, healthy recovery. Also it is never a bad idea to do a PT eval; as you might just find out as I did (a trained phd with many years working in PT and orthopedics) that for example your quads are grossly over trained and tight which is why your knees hurt and why your pelvis is rotated which is why your back has a herniated disc which is why your legs are going numb when you pack an elk quarter out.