There are a variety of things that a treadmill has that causes the problem. One is that running on a treadmill, although being easier than outside, is still a high impact exercise. The force of landing on the belt still causes the shock to go up the leg and through the knee. The shock is absorbed by the knee as it rises.
If you are overweight you may think running on a treadmill is safer than outside but no. The shock of landing on the belt is greater if you're overweight. The knee is still the same whether you're 160 or 200 pounds and it has to deal with the heavier weight somehow. Sometimes it fails and you're left with knee pain.
Running down a hill puts tremendous strain on the knees. The force is more powerful on landing. There are some treadmills that have a decline facility. If you run on this for too long a period of time you might end up with knee pain during or after exercise. You should always keep decline running to a minimum.
The treadmill doesn't change unlike the terrain outside. Outside your knee and supporting ligaments must adapt to the slight corrections it has to make. This doesn't happen on the treadmill so you might have knee pain from a repetitive overuse of the joint. So there are some reasons that a treadmill could be causing you knee pain. But what can we do to help prevent some of these occurring?
How to deal with knee pain
Some knee pain needs slight care while other types need you seeing a physician. The problem is determining which is which. You want to carry on exercising in the shortest period of time so what pain requires what care? Some mild pain can be alleviated with anti inflammatories like ibuprofen.
After exercise if you experience knee pain you may want to elevate the joint and apply ice to it. This is at the same time as resting the knee and applying compression. When you go to bed sleep with a pillow under the knee to help further elevate it for longer. All these methods should help the knee heal quicker and get you back to running again.
There are times when you'll need extra help. In some circumstances if the pain is bad and you struggle with the knee in some other ways then you may need to contact a specialist. If the swelling is particularly bad a medical professional may need to inject the area to further lubricate the joint and make the swelling go down.
Professional help is needed if you can't bear weight on the knee. If you hear clicking or popping sounds then you may need extra help too. If you struggle to straighten or flex the leg and may be the joint doesn't look as it should then a physician may be necessary there. All of this will mean resting the knee until the expert says it's ok to exercise again.
Preventing knee problems
If the cause is your weight and it happens frequently then you may want to consider an exercise that is not so high impact. Try an elliptical or swimming. Both of these stress the knees far less. You can then go back to the treadmill when an amount of weight loss has occurred and your knees won't have to deal with so much impact.
You should do a warm up before you do your main run and cool down. This allows the muscles and joints to prepare themselves for the run that's about to happen and cool down slowly after it has taken place. Rather than put full force on to the knee joints a warm up is mild and therefore prepares the joint. Some dynamic stretching can also help.
Dynamic stretching is different to static where static is holding a stretched pose for 15 to 60 seconds. Dynamic involves bouncing the stretch at it's peak like knee raises up and down. Doing this before and after running helps ease the muscles and joints. Static stretching is now frowned upon and can actually cause problems research has shown.
Strength training of the lower legs will help prevent knee problems a great deal. You can support the muscles around the knee like the hamstrings, calves and quadriceps. Good exercises squats, leg curls and leg extensions. These are all going to help deal with the force of the treadmill belt on the knees as you land.
Be very careful with your knees and if you have persistent pain then see an expert. Professional athletes like football and soccer players tend to have knee replacements when they get older. The knee can only take so much running. Consider exercises that have low impact and alternate these with your running routine.
I'm 44 and I've been running for many years. My left knee can't take a long frequent running routine. It needs rest now and then. Think about when your knee problem occurs. Are you building up the miles too quickly? Are you running a lot faster all of a sudden. Make any changes gradual especially if you're getting older like me.
Remember a knee replacement is never as good as the real thing. I'm probably getting a Peloton Bike and exercising on that so I never have to get a replacement, I haven't decided yet. Always rest if you need to and if it doesn't improve, rest some more or see a doctor who specializes in sports injuries. Go on the side of caution.