Running is a very high impact activity. Landing with each step is equivalent to jumping, even though you may not feel like you are jumping. Up to 3x your body weight is coming down in impactful force on your lower extremities. This is definitely a recipe for knee discomfort.
If you love running and want to continue on a regular basis, it’s important that you strengthen your hips. Your hips help propel you forward and also aid in decelerating as you come back to the ground. Strong hips will keep your knee in an optimal position to reduce stress to the inside of the knee joint. If your knees jut inward as you land, this is an indication of poor hip strength.
Here are some great hip exercises to do 2-3 x per week for increased strength:
Beginners: Start without the ball and place feet on the ground under your knees. Flex your glutes and push upward, lowering slowly and repeating. Advance to using one leg at a time and then to a ball. 20 repetitions.
There are many ways to work the outside of the hip. The simplest is to lie on the ground on your side and raise your leg directly up. Pictured is a slightly more advanced version. Raise and lower slowly for 20 repetitions.
This exercise stabilizes the hip and lower leg, which is great for trail runners. Start with one foot off the ground, tip forward keeping your core tight and the top leg reaching in a straight line. Stand up and try to balance-keeping the foot off the ground for 15 repetitions.
If you don’t have a 6 inch and 12 inch box available, use a first and second stair. Keep all your weight on the stair and step down to tap your heel. Don’t put any weight on the heel. Make sure you are sitting back through your hips and keep your foot firmly planted on the stair. 15 reps each side.