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Weak In The Knees

The idiom getting weak in the knees means to experience a strong emotion after something startles an individual. The thesaurus even shows its synonyms to include getting dizzy or lightheaded; however, this may not mean the same in medical terms. In medical terms, getting weak in the knees means feeling weakness in the knees and legs due to an underlying cause. This weakness may last for minutes, hours, and even days.

Experts believe the individuals should consult a health professional regarding these symptoms, as they may be indicative of fundamental problems with the knees and their surrounding tissues and musculature. If these conditions are not diagnosed and treated at the right time, it may lead to complications for the individual in the long term and affect their quality of life.

What is the cause of being weak in the knees?

The knees are the largest joints in the human body. It is a hinge joint made by joining three bones known as the Shinbone or tibia, the Thighbone or Femur, and the Kneecap bone or Patella. Healthy individuals have functional supporting tissues if the knee joints like cartilages and ligaments, which help maintain joint stability. However, these structures may deteriorate over time due to aging and overuse, leading to knee weakness. The most common causes of Knee Weakness include Osteoarthritis, Quadriceps weakness, and overuse injury. (1)


Studies show that osteoarthritis may be responsible for the deterioration of knee functions and knee weakness in 11% to 56% of individuals compared to healthy individuals. (2)

The difference in knee strength in individuals with and without osteoarthritis maybe even more during eccentric strength tests focused on the knees. Data shows that individuals with osteoarthritis may show 76% deficits in their quadriceps strength tests, which have been conducted at 90 degrees per second and 180 degrees per second. (3)

Osteoarthritis may cause the deterioration of internal structures of the knee joint, leading to its weakness and may also affect the surrounding musculature. Studies have shown that individuals with osteoarthritis may have a 12 percent reduction in the cross-section of their quadriceps, which is linked to a loss of their strength. (4)

Quadriceps Weakness

The quadriceps are responsible for providing functional stability to the knee joint and may also act as shock absorbers preventing trauma to its inner structures. (5) The strength of these quadriceps is directly associated with the load-bearing rates. (6)

Quadriceps are important for protecting the knee from trauma. These muscles provide a cushioning effect and help decelerate the leg movement as an individual starts to walk. This prevents a sudden load on the knee joint and causes potential damage to the internal knee structures. Moreover, strengthening of quadriceps is also proven to prevent knee pain, cartilage loss, and narrowing of the tibiofemoral joint space. (7)

Studies have shown that weakness of the quadriceps and diagnosis of osteoarthritis is often associated with impaired knee stability and knee weakness. It is also associated with the overall deterioration of the physical functions of the surrounding structures.

Although the persistent weakness of the quadriceps is often associated with osteoarthritis, it is not the only cause of its weakness. These may include injuries to the knees, injuries to the hip, Lyme disease, and Poliomyelitis. (8)

Another common cause of quadriceps weakness may be Atherogenic muscle inhibition. This is a condition characterized by a neural inhibition of the muscles that prevent their complete activation. It may be caused by alteration of the discharge of sensory receptors, as seen in a damaged knee. The damaged knee may include inflammation, effusion, laxity, and degeneration of the internal structures. This may lead to muscle weakness and gradual atrophy of the muscle, which in turn will affect its overall strength and the balance of the knee joint. (9)

Overuse injury as a cause of being weak in the knees

Overuse injuries are another common cause of knee weakness and may be commonly seen in athletes and fitness professionals. These injuries are caused by microtraumas in the knee that occur repeatedly and may lead to abnormal joint alignment. They are commonly seen in individuals who undergo poor training techniques and don’t allow their tissues adequate healing time. These overuse injuries affect the knee joint and surrounding tissues due to the close association of the knee joint with surrounding tendons and muscles through numerous attachment points. Overuse injuries may also include tearing ligaments due to sudden trauma or heavy exercise, without giving the body enough time to heal these tears and causing knee weakness. The weakness of these ligaments is what eventually leads to the alteration of functions and stability of the knees. The sprains, internal derangements, and symptoms of a limited range of motion may be further investigated using Magnetic Resonance Imaging Tools. (10)

Diagnosis of Weak Knees

Weakness in the knees may be diagnosed through the major signs and symptoms associated with the condition; however, this is not as accurate as undergoing a proper physical examination and imaging tests. Therefore, an Orthopedic Physician should only diagnose knee problems, which allows them to further determine the cause and design an appropriate treatment. Since the sudden weakness of the knees may indicate underlying medical conditions in the body, it is important to out these root causes and treats them in due time.

The clinician may start by first assessing the nature and severity of the weakness experienced by the patient. The physician may also evaluate the knee’s range of motion during the physical examination. X-ray is an essential diagnostic tool that is often used for the diagnosis of osteoarthritis of the knee – which is a common cause of knee weakness. In income cases, the doctor may also require MRI findings in addition to the X-ray, as they are more clear and allow a better diagnosis.

Treatment Of Weak Knees

As mentioned earlier, the identification of the underlying cause is essential for the treatment of Weak Knees. The factors which are often a focus of interest for the treatment of this condition include reduction of knee pain, discomfort and disability, and improvement of physical functions.

Weight Reduction

Weight reduction is the safest and most unproblematic treatment measure that can be taken for being weak in the knees. This is particularly true for overweight and obese individuals, who are recommended to reach their recommended BMI. This is because it will improve the overall knee instability and protect them from other health issues like hypertension and diabetes mellites type 2. Moreover, studies have also shown that individual who are overweight are more likely to be diagnosed with disorders like osteoarthritis, which increase knee weakness and discomfort. This is because as an individual gains weight, the force on their knees increases by 3 to 6 times. This causes an accelerated deterioration of the knee structures and functional abnormalities in the surrounding supporting structures. (11)

Strengthening Exercise

Strengthening exercises help strengthen the quadriceps muscles, which provide a cushioning effect to the knee joint and are also considered an essential part of the treatment of osteoarthritis. Treatment plans for knee weakness designed by experts all over the world include strengthening exercises, as they not only strengthen the knee joint but also prevent it from getting re-injured.

Physical therapy as a solution for being weak in the knees

Physical therapy and rehabilitation programs are found to be effective in the treatment of knee disorders. Regular physical therapy can help reduce the overall pain intensity and discomfort associated with knee weakness and improve the range of motion and strength of the quadricep muscles. This may be particularly recommended for individuals with moderate levels of pain and knee weakness, as they may benefit the most. The physiotherapist may also recommend some exercises to be practiced at home in accordance with proper footwear. They may also evaluate the patient’s posture and encourage them to correct their posture to lower the load on the knee.


RICE stands for Rest, Ice Compression of the Knee, and Elevation of the leg. This is usually recommended for injuries affecting the knee and lower extremities. As the name suggests, the individual must go on complete rests to allow the knee joint and supporting tissues to heal after knee injuries. In addition, ice therapy helps with inflammation and any swelling affecting the area. Elevating the knee to a level above the heart will also help with the swelling and throbbing in the knee and allow a less painful healing period for the patient.

Knee Braces for being weak in the knees

Knee Brace may be recommended for the stabilization of the knee joint during the application of rotational and anteroposterior forces. These knee braces allow adequate healing of the ligaments and tissue injuries in the knee that may be causing the knee weakness. (12)


In recent years, Prolotherapy has built its reputation within the medical community for its clinically proven ability to treat the root cause of weak knees. Published research has proven its strengthening and stabilising effect on knees.

Prolotherapy involves injecting a natural regenerative solution with small needles, which has been shown to stimulate the production of collagen cells, which the body uses to strengthen structures in and around the knee.

As prolotherapy is helping to treat the root cause of weak knees, it is deemed to be a permanent fix, preventing the weakness from returning.

Frequently Asked Questions:

What to do when you feel weak in the knees?

If you are feeling weak in the knees, you should first opt for finding the leading cause of knee weakness. So, you should consult your doctor for a treatment plan if you have persistent knee weakness or pain. Moreover, you can try:

  • Physical therapy, i.e., knee restoration exercises
  • Nonsteroidal anti-inflammatory medications to relieve pain
  • Knee braces
  • Health supplements
  • Corticosteroid injections

What makes a woman weak in the knees?

The anatomy of the hips makes women weak in the knees. Women have broader hips and weak muscle support than men, and so women have an angled arrangement from the hip to the knees. This angled alignment in women places more pressure on the knee joint than men. So, women feel more weakness in their knees.

How can I rebuild my knee strength?

The best way to rebuild your knee’s strength is through exercise. Don’t worry; you don’t have to do a lot of tough exercises; you just need to focus on such moves that work your lower limb’s muscles, including quadriceps, hamstrings, and gluteus muscles. Just stay consistent with some simple but effective exercises, and you’ll be able to rebuild your knee strength.

Some simple knee exercises are:

  • Knee flexion
  • Knee extension
  • Swimming
  • Wall squats

What foods strengthen knees?

One of the best possible ways to keep your knees healthy and strong is to eat healthy food. To improve your knee health and reduce inflammation, you should eat beans, lentils, omega three fatty acids, olive oil, nuts, seeds, brassica vegetables, whole grains, and fruits.

Why are my knees weak and shaky?

Your knees may be weak or shaky due to inflammatory conditions, systemic disease, or other vascular issues (blood clots or deep vein thrombosis). Your knees may also feel weak due to poor blood circulation. Some other causes are:

  • Infection in knees
  • Knee muscle strain
  • Torn ligament
  • Arthritis
  • Not enough physical activity

Does walking strengthen Knees?

Yes, definitely! Walking is a very simple, easy, and healthy activity that does not stress your knees, builds your knee muscles, and allows them to handle your body weight properly.


  1. Slemenda, C., Brandt, K. D., Heilman, D. K., Mazzuca, S., Braunstein, E. M., Katz, B. P., & Wolinsky, F. D. (1997). Quadriceps weakness and osteoarthritis of the knee. Annals of internal medicine, 127(2), 97–104. https://doi.org/10.7326/0003-4819-127-2-199707150-00001
  2. Diraçoglu, D., Baskent, A., Yagci, I., Ozçakar, L., & Aydin, R. (2009). Isokinetic strength measurements in early knee osteoarthritis. Acta reumatologica portuguesa, 34(1), 72–77.
  3. Hortobágyi, T., Garry, J., Holbert, D., & Devita, P. (2004). Aberrations in the control of quadriceps muscle force in patients with knee osteoarthritis. Arthritis and rheumatism, 51(4), 562–569. https://doi.org/10.1002/art.20545
  4. Ikeda, S., Tsumura, H., & Torisu, T. (2005). Age-related quadriceps-dominant muscle atrophy and incident radiographic knee osteoarthritis. Journal of orthopaedic science : official journal of the Japanese Orthopaedic Association, 10(2), 121–126. https://doi.org/10.1007/s00776-004-0876-2
  5. Hurley M. V. (1999). The role of muscle weakness in the pathogenesis of osteoarthritis. Rheumatic diseases clinics of North America, 25(2), 283–vi. https://doi.org/10.1016/s0889-857x(05)70068-5
  6. Mikesky, A. E., Meyer, A., & Thompson, K. L. (2000). Relationship between quadriceps strength and rate of loading during gait in women. Journal of orthopaedic research : official publication of the Orthopaedic Research Society, 18(2), 171–175. https://doi.org/10.1002/jor.1100180202
  7. Segal, N. A., Glass, N. A., Torner, J., Yang, M., Felson, D. T., Sharma, L., Nevitt, M., & Lewis, C. E. (2010). Quadriceps weakness predicts risk for knee joint space narrowing in women in the MOST cohort. Osteoarthritis and cartilage, 18(6), 769–775. https://doi.org/10.1016/j.joca.2010.02.002
  8. Felson, D. T., Niu, J., McClennan, C., Sack, B., Aliabadi, P., Hunter, D. J., Guermazi, A., & Englund, M. (2007). Knee buckling: prevalence, risk factors, and associated limitations in function. Annals of internal medicine, 147(8), 534–540. https://doi.org/10.7326/0003-4819-147-8-200710160-00005
  9. Young A. (1993). Current issues in arthrogenous inhibition. Annals of the rheumatic diseases, 52(11), 829–834. https://doi.org/10.1136/ard.52.11.829
  10. O’Keeffe, S. A., Hogan, B. A., Eustace, S. J., & Kavanagh, E. C. (2009). Overuse injuries of the knee. Magnetic resonance imaging clinics of North America, 17(4), 725–vii. https://doi.org/10.1016/j.mric.2009.06.010
  11. Huang, M. H., Chen, C. H., Chen, T. W., Weng, M. C., Wang, W. T., & Wang, Y. L. (2000). The effects of weight reduction on the rehabilitation of patients with knee osteoarthritis and obesity. Arthritis care and research : the official journal of the Arthritis Health Professions Association, 13(6), 398–405. https://doi.org/10.1002/1529-0131(200012)13:6<398::aid-art10>3.0.co;2-e
  12. Paluska, S. A., & McKeag, D. B. (2000). Knee braces: current evidence and clinical recommendations for their use. American family physician, 61(2), 411–424.

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