The location of the knee pain can vary depending on which structure is involved. With infection or an inflammatory process, the whole knee might be swollen and painful, while a torn meniscus or fracture of a bone gives symptoms only in one specific location. A Baker cyst will usually cause pain in the back of the knee.

The severity of the joint pain can vary, from a minor ache to a severe and disabling pain.

Some of the other signs and symptoms that accompany knee pain are

• Difficulty weight bearing or walking due to instability of the knee,
• Limping due to discomfort,
• Difficulty walking up or down steps due to ligament damage (sprain),
• Locking of the knee (unable to bend the knee),
• Redness and swelling,
• Inability to extend the knee, and
• Shifting weight to the opposite knee and foot.

What causes knee pain?

Knee pain can be divided into three major categories:

• Acute injury: such as a broken bone, torn ligament, or meniscal tear
• Medical conditions: rheumatoid arthritis, osteoarthritis, infections
• Chronic use/overuse conditions: osteoarthritis, chondromalacia, IT band syndrome, patellar syndromes, tendinitis, and bursitis
• Below is a list of some of the more common causes of knee pain. This is not an all-inclusive list but rather highlights a few common causes of knee pain in each of the above categories.

Acute knee injuries

Fractures: A direct blow to the bony structure can cause one of the bones in the knee to break. This is usually a very obvious and painful knee injury. Most knee fractures are not only painful but will also interfere with the proper functioning of the knee (such as kneecap fracture) or make it very painful to bear weight (such as tibial plateau fracture). All fractures need immediate medical attention. Many fractures require significant force, and a thorough examination is performed to detect other injuries.

Ligament injuries

The most common injury is the ACL (anterior cruciate ligament) injury. An ACL injury is often a sports-related injury due to a sudden stop and change in directions. The remaining ligaments (posterior cruciate ligament, lateral collateral ligament, and medial collateral ligament) are injured less frequently.

Meniscus injuries

The menisci (medial and lateral) are made of cartilage and act as shock absorbers between bones in the knee. Twisting the knee can injure the meniscus.

Dislocation

The knee joint can be dislocated, which is a medical emergency that requires immediate attention. Knee dislocation can compromise blood flow to the leg and have other related problems. This injury often occurs during a motor-vehicle accident when the knee hits the dashboard.

What medical conditions cause knee pain?

Medical conditions

• Rheumatoid arthritis is an autoimmune condition that can affect any joint in the body. It can cause severe pain and disability, as well as swelling.
• Gout is a form of arthritis that is most commonly found in the big toe, though it can also affect the knee. Gout tends to flare up and is extremely painful during the acute episodes. When there is no flare-up, the knee can be pain free.
• With septic arthritis (infectious arthritis), the knee joint can become infected; this leads to pain, swelling, and fever. This condition requires antibiotics and drainage treatments as soon as possible.

Chronic use/overuse conditions

• Patellar tendinitis is an inflammation of the tendons connecting the kneecap (patella) to the shinbone (the bone of the lower leg). Patellar tendinitis is a chronic condition often found in individuals repeating the same motion during exercise (such as runners and cyclists).
• Patellofemoral pain syndrome is caused by degeneration or stress under the kneecap (patella) where it meets the thighbone (femur). Patellofemoral pain syndrome occurs in runners and cyclists.
• Osteoarthritis: a wearing down of cartilage of the joint due to use and age
• Prepatellar bursitis: Inflammation to the bursa (fluid-filled sac) in front of the kneecap may cause anterior knee pain.