What causes hip and knee pain?
It aches on the stairs. It stiffens up after you sit. Some nights the hip keeps you awake and no position helps for long. Your hips and knees absorb impact all day, and they only manage it well when the muscles around them are strong and balanced. When strength or motion goes missing, the joint takes the load instead. An in-depth evaluation is what tells us which joint, which muscle, and which movement started it.
Your hip and knee are only as well aligned as the muscles holding them there. When some muscles are weak and others are tight, the joint sits and tracks slightly off, and every step loads it in a way it was not built for. Nothing about that is dramatic on any single day. Over months it becomes a joint that hurts on stairs and stiffens the moment you sit down.
Even a small difference between your legs changes how force is shared. One knee and one side of the pelvis absorb more than their half, every step, all day. You never feel the difference itself, only the side that keeps complaining about it. This is one of the things a movement and gait assessment is looking for, because the answer is usually strength and mechanics rather than resignation.
Running, jumping and heavy lifting all wear on the protective tissues of the hip and knee. That is normal, and the tissue adapts, as long as there is enough recovery between the loads. Without it, the strain accumulates and turns into pain that shows up on the first step instead of the last mile. The answer is rarely to stop. It is to load and recover in the right proportion.
Years of movement thin the cushioning inside the joint, and bone spurs and ligament changes restrict the motion further. What the imaging shows and what you can do are two different things. Strong muscles around an arthritic joint protect it and keep it moving smoothly, which is why strengthening and mobility work often bring real relief even when the scan looks unimpressive.
Your hip and knee share muscles and nerve supply. If one is stiff or weak, the other compensates, and the compensation is what hurts. It is common for the painful joint to be the one taking the extra work rather than the one that started the problem. That is exactly why the evaluation looks at the whole leg instead of the spot you point to.
The sciatic nerve travels from your lower spine through the hip and down the leg. Joint dysfunction and tight muscles around the hip can compress or irritate it, and the pain then appears well below where the problem actually is. Hands-on work relieves that pressure, but the first job is telling nerve pain apart from joint pain, because the two plans are not the same.
