Everything You Need to Know About Exercising After a Knee Replacement

Knee replacement surgery can help reduce pain and improve function in those with arthritis. You may need to change up your fitness routine, however — especially while you're doing physical therapy. But you can still hit the gym as long as you get permission from your doctor.

"You always want to work with a skilled physical therapist after your knee replacement surgery to ensure you have full knee range of motion, stability, strength and mobility in all of the muscles around your knee," says Grayson Wickham, DPT, CSCS, a certified strength and conditioning specialist, physical therapist and founder of the Movement Vault.

Once you get the OK from your doctor, you can continue your fitness routine at home and in the gym with any modifications they recommend. Generally, the best gym exercises for knee replacement rehabilitation are those that improve range of motion and strength.

For example, a stationary bike is a great cardio option, as it improves mobility and lower-body strength without putting too much impact on your knee. But before getting started, make sure you know the best and the worst exercises after a knee replacement.

Your range of motion after knee replacement will be limited. Your doctor will require you to be able to bend your knee to a 90-degree angle and straighten it before you're discharged. In addition to improving your knee's range of motion, you'll also need to work on strengthening it.

"You want to focus on all of the muscles that surround your knee, including your quadriceps and hamstring muscles," Wickham says. "You will also want to focus on your hip and ankle muscles, which will help keep your knee in a good position while performing exercises and/or your day-to-day activities."

Your physical therapist will teach you exercises to do at home that will help you move your knee more easily and help decrease pain, but there are some simple exercises you can do in addition that can help you progress more quickly.

"Knowing when to perform a specific exercise is key during your rehab process and is why you should always work with a skilled physical therapist after you have a knee replacement," Wickham says.

In general, these exercises can be done three to six weeks after your surgery, per UW Health, but always check with your doctor first.

Step-ups are a functional exercise that strengthen the muscles that support your knee, including the quads, hamstrings and calves. Start with a lower step, around 4 or 6 inches, then progress to taller steps as your strength increases.

Wall squats are another functional exercise that strengthen the muscles that support your knee and hip. Using the wall helps to provide you with some support as your knee heals.

Single-leg balance exercises are important after a knee replacement. You should start this exercise four to six weeks after surgery (pending doctor approval). This will help strengthen the muscles supporting your knee, improve your balance and proprioception (your body's awareness of your leg).

Some people may feel like their new knee is longer than the other. But balancing exercises can help your body become accustomed to your new knee so it doesn't feel quite as foreign.

Strengthening your calf muscle is an important part in helping your walk normally, as well as doing activities like going up and down the stairs.

In addition to the muscles that support your knee, you must also strengthen your hip muscles. This exercise requires you to lie down with your knees bent. If your range of motion isn't at the point where you can do this, continue to work on improving your movement before you do this exercise.

There are also a few other exercises you can do to help your mobility.

Early exercise focus on flexing the joint and coordinating the supportive muscles. Slowly bending your knee while lying in a bed or siting in a chair gets the joint used to movement. Hold the bend for a few seconds and make the entire movement fluid.

Practice walking and climbing stairs with the help of a walker or crutches. It's helpful to have someone with you in the early stages in case you fall. Support your weight evenly and use the walker or crutches until you're no longer putting weight on them.

At this stage, you can switch to using a single crutch or cane on the opposite side from the replaced knee, but stand up straight and try not to favor the new knee. Once you are no longer putting weight on the crutch or cane, you can begin walking unassisted.

Once you're able to walk short distances unassisted, it's important to regain the strength in your leg muscles with resistance exercises. You can do the early rehab exercises with light ankle weights or resistance bands, and you can ride a stationary bike at varying degrees of resistance to strengthen your muscles and work on your range of motion at the same time.

The best exercise machine for knee rehabilitation after surgery will increase range of motion and improve strength. The American Academy of Orthopedic Surgeons (AAOS) recommends exercising for 20 to 30 minutes, two to three times a day, and walking for 30 minutes to regain your strength and mobility after surgery.

The stationary bike is a great post-knee-replacement exercise machine, as it improves range of motion, flexibility and blood flow. The AAOS says to raise the seat of the bike so the bottom of your foot just touches the pedal.

Pedal backward at first, doing partial revolutions, then progress to full revolutions. Once you can pedal backward easily, start pedaling forward. Then add resistance four to six weeks post-surgery. Aim for 10 to 15 minutes twice a day and build your way up to 20 to 30 minutes, three to four times a week, on the bike.

The leg press after knee replacements is another exercise machine that can help you regain strength and function. UW Health recommends the supine leg press with minimal weight (20 to 40 pounds), progressing to more weight as tolerated.

This machine helps strengthen your entire lower leg, which is an important part of recovery. When you're at home, you can replicate this machine with half squats.

Walking is one of the best exercises you can do after surgery. The AAOS recommends initially using a walker and progressing gradually to a cane two to three weeks after surgery. You can stop using a cane once you can walk without a limp.

Once you can move around without a cane, the treadmill is a good post-knee-replacement exercise machine. Keep the incline level low and the speed slow initially, progressing it as your strength and endurance improve. Don't run on the treadmill, though, as this puts too much stress on your new knee.

After your doctor gives you the all-clear to exercise, consider taking yoga or tai chi classes. Both are recommended by the Arthritis Foundation as effective range-of-motion exercises. And both focus on slow, controlled movements and single-leg balance — all important components of post-op recovery.

Yoga poses have variations to accommodate injuries or skill level, and tai chi can help reduce pain and impairment in people with knee problems. When starting yoga after knee surgery, opt for upper-body chair yoga, then gradually transition to restorative or Yin yoga. They're slower and gentler on your joints and incorporate lots of props for support.

Once you're cleared by your doctor, you're free to do any form of yoga — with modifications — that doesn't cause pain. But it's important to learn from a professional, as injury can result from improper form.

It's important to stay active to keep your muscles strong and to maintain a healthy weight, as weight gain can stress your new knee. But there are some exercises that should be avoided or done with precaution after a knee replacement.

The Mayo Clinic states that excessive activity can wear out your artificial knee and cause the replacement to become loose and painful. Therefore, it's safer to avoid high-impact activities, such as running and jumping, or activities that require sudden stops or changes in direction.

Avoid the following activities or do them with caution after talking to your doctor:

• ​Stair step machine:​ Avoid the stair stepper machine immediately after knee replacement surgery, as you may injure yourself until you build up your strength and coordination. The AAOS suggests finding a flight of stairs and using the handrail to go up the stairs with your good knee and down the stairs on your recovering knee.
• ​Leg press with heavy weight:​ Don't lift more than 50 pounds, per UW Health.
• ​Jumping: rope, jacks or box jumps​
• ​Jogging or running​
• ​Sports:​ basketball, tennis, soccer, hockey, skiing, etc.
• ​Driving​: You won't be able to drive right after surgery. You will be cleared to drive around four to six weeks after surgery.
• Exercises that require ​kneeling down​, especially if this is uncomfortable

For best results, stick to low-impact activities and sports including golf, swimming and cycling.

Knee replacement surgery, also known as knee arthroplasty, is an option for people who have severe pain due to osteoarthritis, per the Mayo Clinic. These people have difficulty doing things like walking, climbing stairs and standing up out of a chair.

The procedure involves removing the damaged bone and cartilage from your kneecap, shinbone and thigh bone and replacing it with an artificial joint that's made of special metal alloys, as well as polymers and high-grade plastics.

The surgery has an excellent recovery rate, with more than 90 percent of patients saying they have a big reduction in pain and improved ability to do activities, reports the AAOS.

Plus, you may be able to start moving and exercising your new knee the day after surgery, per the AAOS. Once you're released from the hospital, listen to your physical therapist or doctor, as they can help you choose the best exercise machine for knee rehabilitation.

If you do your prescribed exercises, you can expect to resume your normal activities within three to six weeks and be able to drive four to six weeks after surgery.