Because of its complex range of motion and the weight that’s often distributed through the joint, the knee is vulnerable to injury.
The knee is one of the most complex joints in your body. It can flex, extend, and twist from side to side. Your knees make it possible for you to walk, run, jump, and bend.
Although it can hit you at any age, knee pain becomes more of an issue as we get older. As we age, the tissues become less pliable, brittle, weaker, and more prone to injury.
Wear and tear from daily activities and injuries are some of the most common causes of knee pain, but long-term knee pain can indicate an underlying health issue.
In this article, we group the most common conditions affecting the knee based on their location.
Paying attention to the precise location of your pain can help you narrow down its causes. Use this chart as a guide to possible reasons for your pain.
Pain above your knee can be caused by:
- Quadricep or hamstring tendinitis: Tendinitis happens when the tendons that attach muscles to your bones (quadriceps and hamstrings) become inflamed.
- Arthritis: Knee arthritis happens when the cartilage supporting your knee joint wears out.
- Bursitis: Knee bursitis is the inflammation of sacs of fluid (bursae) located between your knee muscles, bones, and tendons.
The kneecap, or patella, is a bone that covers your knee joint. Pain in this area is sometimes called “runner’s knee.” It’s most commonly caused due to the following:
- Patellofemoral syndrome: Patellofemoral syndrome is the excessive use of the knee joint that can happen if you abruptly start putting strain on your knee, for example, through a new workout routine.
- Chondromalacia patellae: Chondromalacia is the deterioration of the cartilage that covers your kneecap.
- Patellar tracking disorder: Also known as patellar maltracking, this condition occurs when your kneecap isn’t properly aligned.
- Patellar instability: Also known as patellar subluxation, this is a partial dislocation of your kneecap.
- Hoffa’s fat pad impingement: This condition affects a layer of fatty soft tissue just under your kneecap.
- Patella stress fracture: This is a hairline break, which remains in place, of the patella.
- Patellofemoral osteoarthritis: This type of arthritis affects the underside of the patella and the groove in the femur in which the patella sits.
Inner knee pain is typically caused by cartilage deterioration due to injuries. Common conditions related to inner knee pain are:
- Medial collateral ligament (MCL) injury: The MCL runs along the outside of your inner knee to stabilize the joint. An MCL sprain or tear happens if it becomes overstretched.
- Meniscus injury: The meniscus is cartilage that provides a cushion between bones in a joint. A meniscus tear happens if your knee is rotated or put under excessive pressure.
- Pes anserine bursitis: This is an inflammation of the bursa located between the shinbone and three tendons of the hamstring at the inside of the knee.
- Plica syndrome: The plica is a fold in the membrane surrounding your knee joint. Its injury and inflammation can cause plica syndrome. You may notice a snapping in your knee.
- Knee contusion: A knee contusion is a bruise that results from a direct blow to your knee.
Certain underlying conditions can also cause pain in this area:
- Osteoarthritis: Osteoarthritis is a degenerative disease that damages cartilage, causing the bones in your joints to grind together.
- Rheumatoid arthritis: Rheumatoid arthritis (RA) is an autoimmune condition that also breaks down your cartilage.
Many causes of lateral knee pain are similar to those of inner knee pain:
- meniscus tear
- knee contusion
Other causes include:
- Iliotibial band syndrome (ITBS): The iliotibial band is a strip of connective tissue that connects the outer hip to the shinbone. ITBS can happen if you put strain on your iliotibial band by repetitively bending and straightening it. You may notice a snapping in your knee.
- Lateral collateral ligament (LCL) injury: The LCL is located in the knee joint, and it can become strained, sprained, and torn.
- Lateral tibial plateau fracture: A tibial plateau fracture happens when you break or crack the top of the shinbone at the knee.
Pain below the knee can be caused by:
- Patellar tendinitis: Also known as “jumper’s knee,” this condition is caused by injury to the tendon that connects your kneecap to your shinbone.
- Osgood-Schlatter disease: This condition usually happens during growth spurts in children. It causes inflammation in the area where the tendon from the kneecap attaches to the shinbone.
- Osteochondritis dissecans (OCD): OCD happens when bone dies due to avascular necrosis and leads to bone collapse and cartilage damage.
- Sinding-Larsen-Johansson syndrome: Common in children, this condition is caused by inflammation due to excessive use of the patellar tendon.
Pain behind the knee can be caused by some of the conditions discussed below:
- patellar tendinitis
- hamstring tendinitis
- meniscus injury
Other conditions include:
- Baker’s cyst: A Baker’s cyst is a fluid-filled sac that occurs when there’s an excess of fluid between the joints that builds up in your knee, usually due to osteoarthritis.
- Gastrocnemius tendinitis: This condition causes inflammation or degeneration of the tendon of the calf muscle.
- Cruciate ligament injuries: Anterior and posterior cruciate ligament tears happen due to a direct hit to your knee, usually while playing contact sports.
Be sure to talk with a doctor if your knee pain is accompanied by major swelling, significant pain, or fever. In addition, any long-term knee pain should be checked out by a doctor, since it can be a symptom of an underlying health issue.
Get immediate medical attention by calling 911 or local emergency services in the following circumstances:
- Your knee joint looks misshapen or damaged.
- You hear a popping noise during an injury.
- You can’t bear weight on your knee.
- Your pain is intense.
- Your knee swells suddenly and significantly.
To diagnose your knee pain, a medical professional will perform a physical exam and order imaging tests, for example, X-rays or an MRI scan.
Let’s go over some of the questions that people with knee pain often ask doctors.
How can you tell what kind of knee pain you have?
Pay attention to the pain location, its type (sharp or dull), intensity, if it’s accompanied by any other symptoms, and whether you have it all the time or only during a specific activity (for example, bending).
Can you diagnose the cause of your own knee pain at home?
If your pain isn’t significant, you can try to diagnose and treat it at home by paying attention to the specific symptoms you have. However, if home treatments don’t seem to work, make sure to consult with a medical professional.
How do you know if your knee pain is serious?
If you have significant pain and swelling, fever, or other alarming or long lasting symptoms, your pain should be evaluated by a medical professional.
The precise location of your knee pain can help you narrow down the potential cause. In addition to its location, paying attention to its intensity, type, and other symptoms can help you figure out the cause.
However, regardless of the cause, any of the following types of pain should be evaluated by a medical professional:
- not improving
- accompanied by swelling or fever
- makes you unable to bear weight
- impacts your daily activities