The knee is the largest joint in the body, one of the most complex, and one of the joints that suffer the greatest load. The risk of knee injuries and degenerative diseases is high, and few can say they have never experienced knee pain.
In most chronic diseases, the pain is persistent and dull. On the other hand, injuries are characterized by a strong, sudden onset of pain. However, certain conditions can be followed by knee pain, usually sharp, that comes and goes. These attacks and recurrences of pain are activity limiting and may significantly affect the quality of life, especially when one does not know when to expect them.
Keep reading to find out what can cause such pain and what to do to relieve it before seeing a doctor.
What are the potential causes of recurrent sharp knee pain?
Bursitis is inflammation of a bursa – a small, fluid-filled sac that amortizes the friction between two surfaces, usually between muscles and bones, and thus prevents injuries and sprains. Bursae can be found all over the body, especially near large joints, such as the knee.
Any of the knee’s several bursae can get inflamed, but some inflammations are more common than others:
- Prepatellar bursitis, or the housemaid’s knee, is the inflammation of the prepatellar bursa. It is followed by pain and swelling on the front side of the knee and typically occurs in people who spend a lot of time kneeling.
- Pes anserinus bursitis is the inflammation of the bursa lying below the pes anserinus, a shared tendon of several shin muscles. It is associated with overuse and typically occurs in runners. The pain and swelling are located on the inner side of the knee and below it.
Baker’s cyst is a fluid-filled sac that bulges behind the knee. It usually develops in those who already have chronic knee inflammation, usually osteoarthritis, followed by excessive production of synovial fluid. Baker’s cyst forms when this fluid drains towards the popliteal bursa (the bursa behind the knee), which swells and grows, limiting knee mobility and causing pain. As the underlying condition is permanent, Baker’s cyst frequently returns.
Baker’s cyst can develop by the same mechanism after an injury too.
Tendinitis is inflammation of one or more tendons – thick bands of fibrous tissue which connect the muscles and the bones. The patellar tendon usually gets inflamed - a condition also known as jumper’s knee, as it is commonly related to sports that include jumping on hard surfaces. Like bursitis, this is an overuse injury that develops due to repeated stress and worsens over time – even leading to tendon tear! The sharp pain during jumping is common, but it may also be present during running, walking, bending, or straightening the leg.
A gout is a common form of joint inflammation caused by a disorder of uric acid metabolism. Several conditions can lead to either excessive production or insufficient elimination of the uric acid, causing an increase in its blood levels, known as hyperuricemia. This excess uric acid tends to form crystals in joints and soft tissues, and these crystals are a foreign body for the immune system, so – it attacks them, leading to inflammation.
Although the big toe is the most commonly affected by gout arthritis, the knee can be affected too. The inflammation develops suddenly, with sharp pain and swelling, tenderness, warmness, and redness of the affected knee. Arthritis recedes on its own after several days, and, if not treated, it keeps coming and going and becomes chronic over time.
Pseudogout develops through the exact mechanism as gout, only that the crystals in question are not made of uric acid but of calcium pyrophosphate. Unlike gout, pseudogout is not associated with high calcium levels, and the underlying causes for the condition remain unclear.
The knee is the most commonly affected joint. Sharp pain and swelling develop out of nowhere and last for days or weeks. Such episodes repeat and can eventually cause permanent joint damage.
Patellar instability is a condition in which the kneecap tends to partially or completely move from its normal position. This may come as a result of a trauma or be associated with anatomical features of the knee or extreme joint flexibility.
The patients experience pain, swelling, and difficulty moving the affected knee. Most can also recognize that their kneecap has fallen out of place.
Often, the kneecap returns to its place on its own. Sometimes, however, a surgical reposition is necessary.
Sometimes, during a degenerative joint disease, or following an injury, a small piece of bone or cartilage breaks off to find itself floating within the knee joint. Sharp, stabbing knee pain can happen when such a small piece of bone or cartilage gets stuck between the surfaces of the knee joint. This pain comes and goes and can’t be associated with a certain movement or activity. When the fragment moves away, the pain spontaneously disappears.
What can I do to ease the pain?
The first and the easiest thing to do to relieve pain and swelling is the famous RICE:
- Rest– Avoid any activity that would put additional stress on the knee in pain. If possible, try to stay in bed for a day or two.
- Ice– Wrap an ice pack in a towel or a cloth, and apply it to the injured area to reduce bruising, swelling, and pain. Hold for about 15 minutes, and repeat 2-3 times a day for the first day or two.
- Compression – Wrap the painful knee with a compressive bandage to prevent further swelling. Wearing knee stabilizers is also recommended, especially when walking.
- Elevation – While resting, make sure that the injured knee is raised above heart level to reduce swelling.
Non-steroidal anti-inflammatory drugs (NSAIDs) can also be used to diminish pain and inflammation. Apart from pills, which are usually bought over the counter, there are many gels and creams that can be applied directly to the affected area. However, these drugs should be taken with caution. It is best to always consult a doctor or a pharmacist first, especially if one has never taken this type of drug before.
When to see a doctor?
In some cases, the pain will go away spontaneously. However, recurrent pain always demands paying a visit to a doctor and getting proper treatment.
Further, do not hesitate to see a doctor if you experience some of the following:
- The knee is unstable, or you cannot lean on your leg
- You can’t bend, or straighten your knee
- The knee is very swollen, very hot, or very painful
- The pain developed after an injury
- The pain is constant.
- Farha N, Spencer A, McGervey M. Outpatient Evaluation of Knee Pain. Med Clin North Am. 2021;105(1):117-136.
- Saavedra MÁ, Navarro-Zarza JE, et al. Clinical anatomy of the knee. ReumatolClin. 2012-2013; 8 Suppl2:39-45.
- Patel DR, Villalobos A. Evaluation and management of knee pain in young athletes: overuse injuries of the knee. TranslPediatr. 2017;6(3):190-198.
- Abhishek A, Doherty M. Update on calcium pyrophosphate deposition. ClinExpRheumatol. 2016;34(4 Suppl 98):32-8.
- Falkowski AL, Jacobson JA, Kalia V, et al. Cartilage icing and chondrocalcinosis on knee radiographs in the differentiation between gout and calcium pyrophosphate deposition. PLoS One. 2020;15(4):e0231508.
- Demange MK. Baker's cyst. Rev Bras Ortop. 2015;46(6):630-3.