Why Do My Knees Hurt? Understanding the Common Causes of Knee Pain

Knee pain is a very common problem, affecting people of all ages and activity levels. Whether it’s a sharp, sudden pain after a twist or a chronic ache that’s been bothering you for months, understanding why your knees hurt is the first step to finding relief. Knee pain can arise from a multitude of factors, ranging from sudden injuries like ligament tears or cartilage damage to underlying medical conditions such as arthritis and infections.

Fortunately, many instances of minor knee pain can be effectively managed with self-care strategies. Physical therapy and supportive devices like knee braces can also play a significant role in alleviating discomfort. However, in some situations, surgical intervention may be necessary to address the root cause of the knee pain and restore function.

Common Symptoms of Knee Pain

The way your knee pain feels and where it’s located can vary greatly depending on what’s causing it. Along with pain, you might experience other symptoms in your knee, such as:

Swelling and Stiffness: Your knee might feel puffy, tight, and less flexible, especially in the morning or after periods of rest.
Redness and Warmth to the Touch: The skin around your knee might be red and feel warm, indicating inflammation or infection.
Weakness or Instability: Your knee may feel like it’s giving way or unable to support your weight, making it difficult to walk or stand.
Popping or Crunching Noises: You might hear or feel popping, clicking, or grinding sounds in your knee when you move it.
Inability to Fully Straighten the Knee: You may find it difficult to fully extend your leg or straighten your knee.

When Should You See a Doctor for Knee Pain?

While many cases of knee pain can be managed at home, it’s important to know when to seek professional medical advice. Consult your doctor if you experience any of the following:

Inability to bear weight on your knee: If you can’t stand or put weight on your affected knee, or if it feels unstable or buckles.
Significant knee swelling: Noticeable and rapid swelling in your knee joint.
Inability to fully extend or flex your knee: Limited range of motion, unable to straighten or bend your knee completely.
Obvious deformity in your leg or knee: Visible changes in the shape or alignment of your knee or leg.
Fever, redness, pain, and swelling in your knee: These could be signs of an infection.
Severe knee pain associated with an injury: Intense pain immediately following an injury.

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What Causes Knee Pain? Exploring the Reasons

Knee pain can stem from a variety of sources, broadly categorized into injuries, mechanical issues, different types of arthritis, and other medical conditions.

Knee Injuries

Knee injuries are a frequent cause of sudden knee pain, often related to sports or accidents. These injuries can affect various structures in the knee joint.

ACL Injury

The anterior cruciate ligament (ACL) is a crucial ligament in your knee that provides stability. An ACL injury often occurs during sports that involve sudden changes in direction and stops, like soccer and basketball.

An ACL injury involves a tear in the anterior cruciate ligament (ACL), one of the four main ligaments that stabilize your knee joint by connecting your thighbone (femur) to your shinbone (tibia). ACL tears are particularly prevalent in sports with high-impact movements, sudden stops, and changes in direction, such as basketball, soccer, tennis, and volleyball.

Torn Meniscus

A torn meniscus refers to a tear in the C-shaped meniscal cartilage in the knee. Meniscal cartilage acts as a cushion between the shinbone and thighbone. Twisting your knee forcefully while bearing weight can cause a meniscus tear.

The meniscus is a tough, rubbery, C-shaped piece of cartilage that acts as a shock absorber between your shinbone and thighbone. A torn meniscus often happens when you forcefully twist or rotate your knee, especially when putting weight on it.

Other common knee injuries include:

Fractures: Bones around the knee, including the kneecap (patella), can break due to falls, accidents, or even from stepping awkwardly, particularly in individuals with weakened bones from osteoporosis.
Knee Bursitis: Bursae are small fluid-filled sacs that cushion the knee joint. Inflammation of these bursae, known as bursitis, can be caused by direct injury or overuse, leading to knee pain.
Patellar Tendinitis: Also known as jumper’s knee, patellar tendinitis is the inflammation of the patellar tendon, which connects the kneecap to the shinbone. It’s common in athletes who jump frequently, such as basketball and volleyball players, runners, and skiers.

Mechanical Problems

Sometimes, knee pain isn’t from a sudden injury, but from mechanical issues within the knee joint.

Loose Body: Fragments of bone or cartilage can break off due to injury or degeneration and float within the knee joint. These loose bodies may not cause pain unless they interfere with knee movement, acting like an obstruction in the joint.
Iliotibial (IT) Band Syndrome: The iliotibial band is a thick band of tissue running from your hip to the outside of your knee. When this band becomes too tight, it can rub against the outer part of your thighbone, causing pain, especially in long-distance runners and cyclists.
Dislocated Kneecap: A dislocated kneecap (patella) occurs when the triangular bone covering the front of your knee slips out of its normal position, usually to the outside of the knee.
Hip or Foot Pain: Pain in your hip or foot can alter your walking pattern (gait) to compensate for the discomfort. This altered gait can place additional stress on your knee joint, leading to secondary knee pain.

Types of Arthritis

Arthritis, a condition affecting the joints, is a major cause of chronic knee pain. There are over 100 types of arthritis, and several can affect the knees.

Osteoarthritis: Often referred to as degenerative arthritis, osteoarthritis is the most common type. It’s a wear-and-tear condition where the cartilage in the knee joint gradually breaks down over time and with use.
Rheumatoid Arthritis: This is an autoimmune form of arthritis where the body’s immune system attacks the joint lining. Rheumatoid arthritis can affect multiple joints, including the knees, and is known for its debilitating nature and fluctuating severity.
Gout: Gout is a type of arthritis caused by the buildup of uric acid crystals in a joint. While it most commonly affects the big toe, gout can also occur in the knee, causing sudden and severe pain.
Pseudogout: Often confused with gout, pseudogout is caused by calcium-containing crystals forming in the joint fluid. The knee is the most frequently affected joint in pseudogout.
Septic Arthritis: This is a serious condition where the knee joint becomes infected, leading to significant pain, swelling, and redness. Septic arthritis often presents with fever and requires immediate medical attention due to its potential to rapidly damage knee cartilage.

Risk Factors That Increase Knee Pain

Several factors can increase your likelihood of developing knee problems and pain:

Excess Weight: Being overweight or obese significantly increases the stress on your knee joints during everyday activities like walking and stair climbing. Excess weight also accelerates the breakdown of joint cartilage, increasing the risk of osteoarthritis.
Lack of Muscle Flexibility or Strength: Weak or inflexible muscles around the knee can increase the risk of injuries. Strong and flexible muscles support and stabilize the knee joint, helping to prevent pain and injury.
Certain Sports or Occupations: Sports that involve high impact, twisting, or repetitive knee stress, such as skiing, basketball, running, and jobs requiring repetitive kneeling or squatting (like construction or farming), increase the risk of knee problems.
Previous Injury: A past knee injury significantly increases the risk of future knee injuries and problems.

Potential Complications of Untreated Knee Pain

While not all knee pain is serious, ignoring certain types of knee pain can lead to complications. Untreated knee injuries and conditions like osteoarthritis can result in:

Chronic pain: Persistent and ongoing knee pain.
Joint damage: Progressive deterioration of the knee joint structures.
Disability: Reduced mobility and ability to perform daily activities.
Increased risk of future injuries: Weakened or damaged knees are more susceptible to re-injury.

How to Prevent Knee Pain

While preventing all knee pain isn’t always possible, you can take steps to reduce your risk of injuries and joint deterioration:

Maintain a Healthy Weight: Keeping a healthy weight is crucial for knee health. Every extra pound adds stress to your knee joints.
Condition for Sports: Prepare your muscles for sports activities through proper conditioning and warm-up routines.
Use Proper Technique: Ensure you use correct techniques and movement patterns in sports and activities to minimize stress on your knees. Professional guidance can be beneficial.
Strengthen and Stretch: Strengthening the muscles around your knees, especially the quadriceps and hamstrings, provides support and stability. Regular stretching improves flexibility and reduces injury risk. Balance and stability exercises are also beneficial.
Choose Smart Exercise: If you have existing knee pain or arthritis, opt for low-impact exercises like swimming, water aerobics, or cycling, or reduce high-impact activities to protect your knees.

By understanding the potential reasons behind “Why Do My Knees Hurt,” you can take proactive steps towards prevention and seek appropriate treatment when needed. Paying attention to your body and adopting healthy habits can contribute significantly to long-term knee health and pain-free movement.

By Mayo Clinic Staff