The knee is the joint between the bones of the upper and lower leg. It allows the leg to bend and provides stability to support the weight of the body. The knee supports motions such as walking, running, crouching, jumping, and turning.
Several parts help the knee to do its job, including:
Any of these parts are susceptible to disease and injury, which can lead to severe knee pain.
This article breaks down the common causes of severe knee pain into five categories: Trauma, infection, metabolic, degenerative disorders, and connective tissue disorders.
Either direct or gradual trauma can cause knee pain.
The Arthritis Foundation lists the knee as one of the most injury-prone joints.
The overall structure and components of the knee increase the risk for certain types of injury, which can cause pain and prevent full function.
Common knee injuries occur because of tears in one of the three main ligaments of the knee.
- the anterior cruciate ligament (ACL)
- the medial collateral ligament (MCL)
- the posterior cruciate ligament (PCL)
Injuries to these ligaments are common in athletes.
A sudden twisting motion or change in direction can injure the ACL. This is one of the most common knee injuries.
People tend to injure the PCL with direct impact to the area, such as a car crash or football tackle. A direct blow to the knee can lead to MCL damage.
Ligament injuries often require surgery.
Knee trauma can also lead to injuries as a result of overworking or overstretching a tendon. Inflammation, tendinitis, or ruptures can cause knee pain. Engaging in activities that involve the tendons can cause tendon injuries, such as running, jumping, and lifting heavy items.
Patellar tendinitis is the term that describes irritation and inflammation of the patellar tendon in the knee. A severely ruptured tendon usually requires surgical repair.
Less severe cases can be treated with a rigid support called a splint that keeps the knee in a fixed position during the healing process.
An injury that inflames the bursae can lead to bursitis. The bursae are small, fluid-filled sacs that cushion the outside of the knee joint and make it possible for tendons and ligaments to glide easily over the joints.
A sudden blow to the front of the knee can injure the bursae. Alternatively, damage can occur if people spend a lot of time on their knees without protection. Bursitis can lead to swelling, warmth, pain, and stiffness in the knee.
Most people can resolve the symptoms of bursitis with therapy and oral medications, such as non-steroidal anti-inflammatory drugs (NSAIDs). Therapy can include rest, ice, elevation of the limb, and splinting.
People with serious bursitis might require steroid injections. Individuals will not normally need surgery to make a full recovery and will normally achieve full function with proper management and treatment.
Trauma from a fall or collision can cause fractures in the bones of the knee.
The knee contains several bones that can break, including the kneecap, also known as the patella.
Individuals with osteoporosis or other degenerative disorders that weaken bones can fracture their knee simply by stepping off a curb in the wrong way. Serious fractures require surgery, but some people with a knee fracture need only physical therapy.
Some injuries can cause the kneecap to move out of place.
Often, a doctor can replace the kneecap without issue. An X-ray can identify any accompanying fractures in the area. The individual may have to use a splint to allow the soft tissue around the patella to heal and regain strength. Occasionally, a person will require surgery to prevent further dislocations.
A dislocated knee is a rare but dangerous injury and differs from a dislocated kneecap. It takes a highly powerful blow to cause this type of damage. Though reversible, dislocation of the knee is extremely painful.
The doctor must reduce the dislocation and ensure that there are no further injuries. Injuries to the blood vessels and nerves around the knee are common with this injury, and it can be limb-threatening and life-threatening.
A doctor will almost always recommend surgery to repair the damaged structures in a knee dislocation. It can take about 6 weeks to heal from a dislocated kneecap.
This a medical emergency and requires immediate clinical attention.
Degenerative tissue disorders
Degenerative tissue disorders are a common knee complaint.
Osteoarthritis causes degeneration in the cartilage and surrounding tissues of the knee. It can produce pain, stiffness, and joint dysfunction.
The degenerative condition occurs most commonly as a result of aging. It occurs in 10 percent of men and 13 percent of women over the age of 60 years in the United States.
Although there is no cure for this degenerative disease, people can manage the symptoms with gentle exercise and pain relief medications.
Severe damage may lead to joint replacement or other forms of surgery. A doctor will initially order an X-ray to assess the extent of the damage and decide on the best course of treatment.
Connective tissue disorders
Rheumatoid arthritis can be a cause of knee pain.
Rheumatoid arthritis (RA) is an inflammatory autoimmune disorder that affects the joints.
The immune system attacks the joint tissues instead of harmful elements in the body.
Unlike degenerative tissue disorders, RA and other connective tissue disorders affect the lining of the joints. The result is a painful swelling in the knee joints. If a person does not receive treatment, RA can lead to bone erosion and even joint deformity.
Even though the pain might only occur in the knee area, RA can damage other parts of the body. Discuss treatment options with a doctor.
There is no cure for RA, but medication and treatment options are available. NSAIDs, corticosteroids, and biological agents are a few of the possible treatments, as well as disease-modifying anti-rheumatic drugs (DMARDs).
Metabolic causes of knee pain often occur alongside a disease that affects several parts of the body, such as gout.
A build-up of uric acid crystals in the joints can cause gout, one of the most common metabolic complaints that can affect the knee.
A doctor will often recommend anti-inflammatory medications or other treatments that help break down the chemicals in gout crystals.
Pseudogout is a similar condition. People commonly mistake this for gout, and it causes calcium-containing crystals to develop in the joint fluid, leading to swelling in the knee.
Treatment for gout and pseudogout are often similar.
Infection can even occur after a simple scrape on the knee if a person does not receive treatment for cellulitis. Symptoms often include redness in the infected area and skin that feels hot and extremely tender to the touch.
Infection can occur in the knee, but ice packs are a helpful way to soothe the discomfort.
The infection can spread to other areas of the body, including the lymph nodes and bloodstream. Cellulitis can be life-threatening if there are delays in treatment.
Pay close attention to any scrapes or bruises, especially if they do not seem to be healing.
In most cases, an individual can treat cellulitis by taking antibiotics. Signs and symptoms normally disappear within a few days of treatment.
Treatment is simple and effective if a person quickly receives care for septic arthritis, but leaving the infection untreated can lead to permanent damage to the cartilage of the knee.
Talk to a doctor
A trained medical professional should perform tests to determine the direct cause of any knee pain.
They may reach a diagnosis by asking the following questions:
- When and how did the pain start?
- Is the pain linked to an injury?
- How severe is the pain?
- How has the pain changed over time?
- What makes the pain worse and what makes it feel better?
- What treatment has taken place so far?
- Has this ever happened before?
The doctor will be able to recommend a course of treatment appropriate for the cause of the pain.
What is the best way to identify the cause of my knee pain?
The best way to manage knee pain is to identify the cause, as follows:
- Metabolic causes: Is there a history of gout or symptoms including dehydration that could precipitate a gout attack? If you have a diagnosis of gout, are you managing the condition with medication? Keeping up your regimen could reduce knee pain.
- Trauma: You will normally be aware of what causes a trauma, unless it is a repetitive type of trauma, such as a sudden and drastic increase in running distance.
- Infection: Is the joint red, hot, or swollen? Does the patient have a history of infections elsewhere or a compromised immune system? An elevated temperature is also a sign of infection in the knee.
- Osteoarthritis: Was the onset gradual or sudden? With OA, the pain usually develops gradually. Excessive body weight is one of the more common findings in people with osteoarthritis of the knee, so if you are overweight, this could be contributing to knee pain.
- Connective tissue disorders: Do you have a pre-existing diagnosis of a connective tissue disorder? If so, have you been taking medications to control it? Are there other joints involved, as with rheumatoid arthritis? If one knee is involved, a connective tissue disorder will likely affect the other knee.