Weak knees: causes, exercises, and tips

You may have gone “weak in the knees” when you first saw your high school crush or before giving a presentation to a large audience. But if your knees feel unstable or give out during everyday activities, it's more than just feeling nervous — it could be a sign of knee weakness. 

“Knee weakness is one of the most common reasons I see patients,” says Aashini Govani, PT, DPT, a physical therapist at Hinge Health. Weak knees themselves aren’t a cause for alarm, Dr. Govani adds. But, left unaddressed and without strengthening, knee weakness can gradually lead to knee pain and stiffness. This can limit your ability to stay active.

Here, we'll take a closer look at weak knees — what they are, how they feel, common causes, and treatment options. You'll also find exercises recommended by Hinge Health physical therapists to help strengthen and support your knees.

What are weak knees?

“Weak knees” isn’t a formal medical diagnosis. Instead, it describes a feeling of instability and lack of strength in your knee joints that can make everyday movements challenging and uncomfortable. 

“Everyone experiences knee weakness differently,” explains Dr. Govani. “Some people might have mild knee pain after a challenging workout. Others may feel like their knees will give out when they stand up from a chair or go down the stairs.”

Although weak knees can be concerning, they’re usually not serious and often improve with exercise and lifestyle changes. Building up the muscles around your knees can treat knee weakness, make everyday movements easier, and help relieve knee pain.

Why do my knees feel weak? 6 causes

Anyone can experience weak knees, regardless of age or activity level. Causes range from past injuries to natural age-related muscle loss. Even trying new activities or repetitive movements can temporarily make your knees feel weak as they adapt. Strengthening the surrounding muscles and incorporating a variety of movements can help your knees feel stronger and support an active lifestyle. Here are some of the most common reasons you might develop weak knees:

• Lack of muscle strength. “This is one of the most common contributors to weak knees that I see,” says Dr. Govani. “Several muscles surround your knees: your quads, hamstrings, and calves,” she explains. “These muscles work together to help your knees move properly. If any of them are weak, it can affect how your entire knee joint moves.” 

• Ligament injuries. There are four major ligaments in each knee: anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL). “Injury to any of these ligaments can cause knee weakness,” explains Dr. Govani, “because the ligaments aren’t able to support your knee as well during movement.”

• Meniscus injuries. The meniscus is the cartilage that cushions your knee joint between the thighbone and shinbone. It can be affected by injuries such as strains or tears. These issues may develop from sudden twisting movements during sports or simply as a part of aging. If the meniscus becomes injured, you might notice knee weakness, sometimes due to discomfort or favoring your other leg, which can lead to temporary muscle loss.

• Repetitive activities. Even if you don’t have knee issues all the time, you may notice knee weakness when you try a new activity. “Your knees can become accustomed to certain movements — for example, the forward and backward motion of running — but may not be as prepared for sudden direction changes required in sports like pickleball,” explains Dr. Govani. “That’s why cross-training is so important. Incorporating a variety of movements into your routine helps build knee strength and reduces the risk of weakness.”

• Sarcopenia. This is a fancy term for normal age-related muscle loss. On average, adults lose about 3 to 8% of their muscle mass per decade after age 30, and this accelerates after age 60. “Your knees are built to handle a lot of weight and stress, but changes in surrounding muscles can still make them feel weaker,” explains Dr. Govani. 

• Osteoarthritis. This common joint condition can make your knees feel achy, stiff, or unsteady. With osteoarthritis, changes in the knee joint may cause irritation and decrease flexibility, which can contribute to weakness or difficulty moving around. Discomfort sometimes leads people to favor the opposite leg or limit activity, which can gradually result in even more weakness in the knee over time.

Symptoms of weak knees

While weak knees can cause pain, symptoms are often more subtle, says Dr. Govani. Common signs of knee weakness include feelings of instability or wobbliness, difficulty rising from a seated position, stiffness, muscle fatigue after activity or standing, and ongoing achiness. Here's what you may notice:

• Your knees feel unstable or wobbly. You might feel as though your knees could give out, even if you’re standing still.

• Difficulty rising from a seated position. “Patients often tell me it’s challenging to get up from the toilet or out of the car,” says Dr. Govani.

• Knee stiffness. Bending and straightening your knee may become more difficult.

• Muscle fatigue. Your knees might feel tired after physical activity or even after standing for long periods.

• Achiness. “Weak knees don’t usually cause sharp pain,” explains Dr. Govani. “It’s more of a persistent discomfort that can make everyday activities challenging.”

These exercises, recommended by Hinge Health physical therapists, are designed to strengthen the muscles that support your knees. You can do them anywhere, anytime, making it easy to fit movement into your day. Dr. Govani suggests aiming to add these exercises to your routine at least three times a week if you have weak knees. “Movement is medicine when it comes to keeping your knees healthy and strong,” she notes. 

The information contained in these videos is intended to be used for educational purposes only and does not constitute medical advice or treatment for any specific condition. Hinge Health is not your healthcare provider and is not responsible for any injury sustained or exacerbated by your use of or participation in these exercises. Please consult with your healthcare provider with any questions you may have about your medical condition or treatment.

Treatments for weak knees 

You don’t have to let weak knees keep you from doing the activities you love. There’s a lot you can do to improve your knee strength, says Dr. Govani. Here’s what Hinge Health physical therapists recommend:

• Physical therapy and targeted exercises. Targeted exercises strengthen the muscles surrounding your knees and help reduce discomfort. The exercises listed above are a great place to start, but you can also do exercise therapy at home or work with a physical therapist who can guide you through movements tailored to your needs. You can see a physical therapist in person or use a program like Hinge Health, where you may access a PT via telehealth/video visit.

• Gentle movement. "People often hesitate to bear weight on weak knees, but in most cases, that is precisely what's needed," says Dr. Govani. You can start with low-impact exercises like swimming or cycling to build confidence and gently strengthen your knees. This helps activate and build the muscles that support the knee joint and makes it easier to progress to higher-impact activities such as running or jumping as your strength improves. 

• Over-the-counter (OTC) medication. Pain relievers such as ibuprofen (Advil, Motrin), naproxen (Aleve), and acetaminophen (Tylenol) can help ease pain associated with knee weakness so you can perform your targeted exercises and stay active. Other options include topical NSAIDs or pain relief creams. If you have a medical condition or take other medications, check in with your provider to make sure these OTC options are ‌safe to take.

• Massage. Massage can improve pain and function in people with knee weakness. Research shows it can be especially helpful for those with knee osteoarthritis, a common cause of knee weakness. Dr. Govani explains that weak knees can lead to tension in the surrounding muscles, tendons, and ligaments as they respond to strain. Massage helps relax these tissues and relieve pain related to weakness. 

• Knee brace. If weak knees make certain activities difficult, wearing a knee brace during those activities can provide some much-needed support, says Dr. Govani. But you don’t want to wear a brace all the time. Bracing should be a short-term tool that helps you stay active while you work on building up the muscles around your knees. "If worn too often, braces can actually weaken your knees because the brace prevents your knees from being challenged — and therefore, getting stronger — during everyday movements.” 

When to see a doctor 

Knee weakness often improves on its own with conservative treatments. But if it’s getting worse or causes difficulty with daily activities, see a healthcare provider. It’s also a good idea to get care if you have:

• Repetitive falls 

• Knee instability or feeling like your knee will give out when you walk 

• Worsening knee pain or swelling 

• Redness and warmth over the area

• Radiating pain that doesn't get better

PT tip: Strengthen as you sit

“You don’t need to go to the gym or do only squats and lunges to build knee strength,” says Dr. Govani. "Strengthening exercises can be just as effective when done right from your chair." Try simple moves like seated marches, seated leg raises, or glute squeezes while you’re at your desk or relaxing on the couch. These take just a few moments, but doing them regularly can add up to healthier, stronger knees. 

How Hinge Health can help you

If you have joint or muscle pain that makes it hard to move, you can get the relief you’ve been looking for with Hinge Health’s online exercise therapy program.

The best part: You don’t have to leave your home because our program is digital. That means you can easily get the care you need through our app when and where it works for you.

Through our program, you’ll have access to therapeutic exercises and stretches for your condition. Additionally, you’ll have a personal care team to guide, support, and tailor our program to you.

See if you qualify for Hinge Health and confirm free coverage through your employer or benefit plan here.

This article and its contents are provided for educational and informational purposes only and do not constitute medical advice or professional services specific to you or your medical condition.

References 

1. Volpi, E., Nazemi, R., & Fujita, S. (2004). Muscle tissue changes with aging. Current Opinion in Clinical Nutrition and Metabolic Care, 7(4), 405–410. doi:10.1097/01.mco.0000134362.76653.b2

2. Perlman, A., Fogerite, S. G., Glass, O., Bechard, E., Ali, A., Njike, V. Y., Pieper, C., Dmitrieva, N. O., Luciano, A., Rosenberger, L., Keever, T., Milak, C., Finkelstein, E. A., Mahon, G., Campanile, G., Cotter, A., & Katz, D. L. (2018). Efficacy and Safety of Massage for Osteoarthritis of the Knee: a Randomized Clinical Trial. Journal of General Internal Medicine, 34(3). doi:10.1007/s11606-018-4763-5

3. Veronese, N., Koyanagi, A., Stubbs, B., Cooper, C., Guglielmi, G., Rizzoli, R., Punzi, L., Rogoli, D., Caruso, M. G., Rotolo, O., Notarnicola, M., Al-Daghri, N., Smith, L., Reginster, J.-Y., & Maggi, S. (2019). Mediterranean diet and knee osteoarthritis outcomes: A longitudinal cohort study. Clinical Nutrition, 38(6), 2735–2739. doi:10.1016/j.clnu.2018.11.032

4. Mulcahey, M. K. (2022, February). Common Knee Injuries. Ortho Info — American Academy of Orthopaedic Surgeons. Retrived from https://orthoinfo.aaos.org/en/diseases--conditions/common-knee-injuries/

5. Wittstein, J. R. (2025, May). Meniscus Tears. Ortho Info — American Academy of Orthopaedic Surgeons. Retrived from https://orthoinfo.aaos.org/en/diseases--conditions/meniscus-tears/