Exercises for an Unstable Knee: A Physical Therapist's Starter Program

Before you start

• Know the cause. The right program for a torn ACL, a meniscus tear, or arthritis differs in the details, so an evaluation is worth it.
• Mild discomfort that settles within a day is generally OK. Sharp pain is not.
• Stop and get checked if the knee swells more the next day, locks, or gives way during the exercises.
• For standing exercises, keep a counter or sturdy chair within reach, and wear your brace if your knee gives way while standing.

The starter program

• Quad sets. Sit or lie with your leg straight. Tighten the front of your thigh, pressing the back of your knee toward the floor. Hold 5 seconds. Do 10 to 15.
• Straight-leg raise. Lie on your back with the other knee bent. Tighten your thigh, lift the straight leg to the height of the bent knee, and lower it slowly. Do 2 to 3 sets of 10.
• Bridges. Lie on your back with both knees bent. Squeeze your buttocks and lift your hips until your body is straight from shoulders to knees. Do 2 to 3 sets of 10 to 12.
• Side-lying leg raise. Lie on your side, bottom knee bent. Lift the top leg, kept straight and slightly behind you, then lower it slowly. Do 2 to 3 sets of 10 on each side.
• Sit-to-stand. Stand up from a chair without using your hands if you can, keeping your knees in line with your toes, then sit back down slowly. Do 2 to 3 sets of 8 to 12.
• Step-ups. Step onto a 4- to 6-inch step, keeping your knee over the middle of your foot rather than letting it cave inward. Do 2 to 3 sets of 8 to 10 on each leg.
• Standing hamstring curl. Holding a counter, bend your knee to bring your heel toward your buttocks, then lower it slowly. Do 2 to 3 sets of 10.
• Single-leg balance. Stand on one leg near a counter for 30 seconds. Do 3 on each leg.

How to progress

When 3 sets of an exercise feel easy, make it harder: add an ankle weight, lower more slowly, use a lower chair, or use a higher step. Turn step-ups into slow step-downs, which train the same control you need on stairs, where knees often give way. For balance, try closing your eyes, standing on a pillow, or reaching in different directions.

As the exercises get harder, 2 to 3 strength sessions a week with rest days in between work well. Consistency matters more than intensity: meaningful strength gains usually take 6 to 12 weeks.

Using a brace while you get stronger

Strength takes weeks to build, and your knee still has to get you through work, errands, and the activities you enjoy in the meantime. A brace can support the knee during those activities so you can stay active while the muscles catch up. It doesn't replace the exercises, and the exercises don't replace a brace on the days your knee is least reliable.

Common questions

How long before exercises make my knee feel more stable?

Some people notice better control within a few weeks, because balance and muscle activation improve quickly. Real strength gains usually take 6 to 12 weeks of consistent work.

Should I avoid squats if my knee is unstable?

Partial squats and sit-to-stands are usually safe and useful. Hold off on deep, heavily loaded squats, jumping, and pivoting until your strength and control improve.

Is walking good for an unstable knee?

Generally yes. Start on flat, even ground, build up gradually, and consider a brace for uneven ground or longer distances where your knee tends to give way.

Sources

• AAOS OrthoInfo: Knee Conditioning Program
• AAOS OrthoInfo: Knee Exercises
• AAOS OrthoInfo: Arthritis of the Knee