I had knee problems for a while and, while it didn’t slow down my workouts, I would be in a great deal of pain after. Then I discovered pre-workout squats and everything changed. What worked for me may not necessarily work for everyone though.
It’s easy to come up with excuses when you don’t want to exercise. “I have bad knees” is one of many. However, reducing your activity level may weaken your muscles and make the problem worse. Don’t let knee problems get in the way of your health; there are plenty of exercises that put very little strain on your knees. Managing your knee health with exercises such as stretching, and physical therapy is required to avoiding costly surgeries or pain medications overuse.

Dos and Don’ts
Keep this list in mind whenever you’re doing something physical to avoid aggravating the condition of your knees or worsening a recent injury.

DON’T: participate in sports that require sudden stopping and starting, jumping, and twisting. These movements put undue pressure on your knee joints.
DO: try activities such as swimming and low-impact cycling that will strengthen your leg muscles and improve your cardiovascular health, while being gentle on your knees.

DON’T: do high-impact exercises.
DO: consider joining a yoga or Pilates class. These classes offer full body workouts that focus on core strength, breathing, and stretching. A qualified instructor will be able to guide you into poses that support knee health. You can apply these lessons to everyday activities, such as walking up stairs and lifting heavy objects. You may find more pain-free patterns of movement by correcting bad habits and mobilizing the knee joint properly.

Helpful Stretching Exercise
Here are a few stretching exercises you can try at home, regardless of the cause of your knee pain. Remember to warm up your muscles gently before stretching.

Quadriceps Stretch
Your quadriceps (quads) are a group of muscles located on the front of your thighs. One of their functions is to extend your knee joint.
Stand facing a wall. Place your left fingertips on the wall for balance. Bend your right knee and reach back for your right ankle with your free hand. Gently pull your foot towards your buttocks until you feel a stretch. Hold for 30 seconds then repeat on the other side. If this is too challenging, wrap a belt or a tie around your ankle and grab the belt with your free hand for more slack.

Hamstring Stretch
Your hamstrings are located on the backs of your thighs and knees. They flex your knee joint. If you sit down for much of the day, you probably have tight hamstrings.

Lie on your back. Bend your left knee and place the foot on the floor. Raise your right leg. Take a strap (a belt, or a tie) and loop it around the ball of your foot. Grab the strap with your hands and pull your foot towards your face. Stop when you feel a stretch in the back of your thigh. Keep just a slight bend in the right knee as you do this. Hold for 30 seconds then repeat on the other side.

Iliotibial Band Stretch
Your iliotibial band, the IT band, is a thick band of tissue located on your outer thighs. It crosses both hip and knee joints and is responsible for stabilizing your knee joint.
Stand up straight and cross your left foot over your right foot. Place your left hand on your hip and lean your upper body to the left, pushing your right hip to the right. Your inner thighs will press strongly against each other. Pause when you feel a stretch in your outer right hip or thigh. Hold for 30 seconds then repeat on the other side.
Only certain knee workouts are safe and effective for bad knees. Your capabilities will depend on your injury, but the following knee exercises can often be done with ease, even with bad knees. Check with your doctor or physical therapist before beginning any “bad-knee” workout.

Works: Gluteus, hamstrings, quads.

-Standing in front of a staircase, place one foot flat on the bottom step. (You also can use a step bench.)
-Make sure your entire foot is on the step and your knee is directly above your ankle.
-Putting your weight on the heel of your elevated foot, step onto the foot, lift the opposite foot and tap the step and the floor.
-Switch when you’ve completed at least 10 reps.
-To make this bad-knee workout even more effective, do curls with light weights each time you step up.

Partial squats
Works: Knees, quads
Although full squats are among the worst bad-knee exercises (though they work for me), partial squats are actually one of the best.

-Start by positioning your feet shoulder-width apart, toes pointed forward.
-Flex your abs while lowering your upper body as low as comfort will allow. Your knees should remain behind your toes throughout the exercise.
-Find a good knee support product before attempting this exercise, and never workout alone.

Calf raises
Works: Lower-leg muscles.

-Stand up straight with the front of your feet on a flat surface.
-Keep your ankles, hips and shoulders in perfect alignment, toes pointed forward.
-Lift your heels very slowly, then lower them at the same speed.
-The slower you raise and lower your body, the better the workout. Start with 25 reps.

Scissor kick
Works: Abs, hip flexors, thighs.

-Lie flat on your back with your legs together and arms by your sides.
-With your forearms on the ground, lift your legs six inches and your shoulders one inch.
-Holding that position, spread your legs apart, bring them back toward each other, then cross one leg over the other.
-This is one rep. Start by doing sets of 50 reps. Don’t let your legs or shoulders rest on the floor during the set.

Works: Upper, mid and lower body muscles.

Swimming is one of the best exercises for people with bad knees. It’s low-impact and versatile, and it burns calories fast. Proper form is crucial, especially in kicking. The knees should not be tensed. Techniques that put stress on the knees (e.g., the frog kick) should be avoided. Also, avoid the traditional pre-lap push off the wall.

Speed walking
Works: Upper, mid and lower body muscles.
Running and jogging put stress on bad knees, but speed walking is low-impact and great exercise for the whole body. Beginners should stick to flat, smooth surfaces. After your walking muscles are strengthened, you may even be able to take low-impact hikes.
Cardio exercise for bad knees doesn’t have to cause even more knee pain.

Low-impact cardio ideas
While cardio is important to achieve your fitness goals, it can be hard on your body. Over time, high-impact cardio, like running, can give way to muscle and joint injuries. To minimize the risk of injuring yourself, try different methods of low-impact cardio. Here are five low-impact cardio activities that will give you the results you want, while taking it easy on your body.

Take a dance class
Whether it is ballet, tap, salsa or modern, dance classes are wonderful low-impact cardio activities that keep your heart rate up for long periods of time. By requiring you to warm up first and stretch your muscles throughout the class, dance classes are also good for your body.

Use the elliptical instead of the treadmill
You will burn roughly the same amount of calories using an elliptical trainer as you would in the same amount of time on a treadmill. Plus, your feet never leave the pedals, so there is less chance of injuring your knees, back, neck or hips. This is an exercise that your body will thank you for, as it is essentially running on air.

Dust off your bike
Grab your bike out of the garage or storage and go for a bike ride. If you don’t have one, you can use the stationary bike at your gym. Cycling will build your endurance and, depending on how fast you go, will burn between 250-500 calories in 30 minutes. If you are cycling indoors, using the traditional stationary bike instead of the sitting stationary bike will burn more calories, as it engages more of your muscles in the exercise.

Walk it out
Going for a good, old-fashioned walk has numerous health benefits and is a classic form of low-impact cardio. Make sure to stretch first, wear supportive footwear and keep your pace brisk to get the maximum results from this low-impact exercise.
Finding the right kind of cardio for you is important. You can be challenged and stimulated without hurting yourself or taking your body beyond the point it can handle. Try switching back and forth between these low-impact cardio exercises throughout the week to keep your muscles engaged and your workout routine challenging.