What Causes Inner and Outer Knee Pain?

Soreness on the inside or outside part of the knee is common, and several different conditions may be to blame. Read more about the many potential causes of pain on the side of your knee and about the treatments available for your symptoms.  

Causes of Inner Knee Pain

The inside or medial part of the knee contains a wide variety of bones, ligaments, and soft tissue structures, all contained within a relatively small area. Because of this, pain in this area of the joint can be tough to diagnose.

Several of the most common conditions that cause medial knee symptoms are listed below.

Osteoarthritis

Osteoarthritis (OA) in the knee occurs when the smooth, slippery cartilage that coats the end of your thigh bone (femur) and lower leg bone (tibia) begins to thin and deteriorate. As this happens, friction increases in the joint and the normal movement of your knee is altered. This increased friction can also cause new bone to develop within the joint, further limiting your range of motion.

OA frequently affects the medial portion (called the medial tibiofemoral compartment) of the knee, leading to pain on the inside of the joint.

Soreness and stiffness are also common complaints with OA, particularly in the morning and after sitting for an extended period of time. Other symptoms include:

• Swelling
• Weakness
• Popping and grinding
• Giving way of the knee

Medial Meniscus Tear

The meniscus is actually two firm pieces of cartilage that are located between the femur and tibia bones in your knee joint. This tough structure helps absorb the forces placed on your knee and functions like a cushion for the area.

Occasionally, the medial portion of your meniscus can tear and lead to pain on the inside of the knee. Sometimes this type of injury occurs suddenly after the leg is twisted while playing sports or exercising. In other cases, a medial meniscus tear occurs in older individuals as a result of cartilage wear and tear over time.

In addition to inside knee pain, a medial meniscus tear can also cause:

• Catching or locking of the knee joint
• Swelling and stiffness
• Being unable to fully straighten or bend your knee

To add to this, this condition can make your knee feel unstable and actually cause it to give way while you are walking.

MCL sprain

The medial collateral ligament or MCL is a firm band of tissue that runs from the femur to the tibia on the inside of your knee. This ligament provides stability to this area and helps prevent the knee from buckling inwards. Occasionally, this structure can be overstretched (called a sprain) or even torn (either partially or completely).

An MCL tear commonly occurs as a result of a sudden twist, bend, or change of direction. Because of this, it is frequently injured while playing sports like soccer, football, or basketball. It can also be sprained or torn as the result of a direct blow to the outside of the knee joint.

Aside from inner knee pain, this condition typically results in:

• Sudden swelling that develops shortly after the initial injury
• Popping on the outside of the joint
• Knee stiffness and bruising
• Overall feelings of instability

Pes Anserine Bursitis

One less common cause of inner knee pain is pes anserine bursitis. This condition occurs when a bursa (a fluid-filled sac that helps reduce friction between bones and tendons) located near the inner knee becomes inflamed. This bursa separates the tibia bone from three muscle tendons (the gracilis, the sartorius, and the semitendinosus) that insert near it.

Pes anserine bursitis is particularly common in individuals who participate in repetitive sports, like running or biking, as they can cause increased friction on the bursa. The pain from this condition is usually located about two to three inches below the inner knee joint. Typically, the soreness increases with exercise or when climbing stairs, and reduces or resolves with rest.

Causes of Outer Knee Pain

Like the inside of your knee, the outside or lateral portion of the joint is a crossroads of many different anatomical structures. This can make getting to the bottom of pain in this area equally frustrating. If you have soreness near the lateral part of your knee, the most frequently seen causes are listed below. 

Osteoarthritis

Along with the inside compartment of the knee and the back of the knee cap, osteoarthritis (OA) can also affect the lateral portion (called the lateral tibiofemoral compartment). OA in this area is a common reason for pain and soreness on the outside of your knee.

This condition’s symptoms closely mirror those described for medial knee osteoarthritis. The most typical lateral OA symptoms include:

• Morning stiffness
• Restricted range of motion
• Noise (called crepitus) with movement
• Weakness
• Occasional giving way of the leg

Lateral Meniscus Tear

The outside portion of your meniscus is also prone to tearing, either suddenly after a twisting injury or as a result of degeneration over time. Lateral meniscal tears are another frequently seen reason for focal pain on the outside of the knee joint.

Other symptoms associated with this type of cartilage damage include:

• Swelling
• Stiffness
• Locking
• Giving way at the joint

Range of motion may also be limited, making it hard to extend or flex your knee.

LCL sprain

The lateral collateral ligament or LCL is a thinner band of tissue that spans from the femur bone to the fibula (a smaller bone on the outside of the lower leg). This structure provides stability to the knee joint by preventing it from bowing outwards.

Similar to the MCL, this ligament is most frequently sprained or torn after a cut or change in direction. Start and stop movements or direct blows to the inside of the knee can also be to blame.

Following an LCL sprain or tear, you may feel:

• A pop
• Swelling
• Pain
• Unstable

Additionally, because the ligament is located close to a structure called the peroneal nerve, an LCL injury may also lead to numbness or tingling in your foot.

IT Band Syndrome

Iliotibial (IT) band syndrome is another cause of lateral knee pain that is particularly common in runners. The IT band is a long, thick strip of connective tissue that runs down the outside of your thigh from the pelvis to the knee.

This condition is thought to occur when the bottom portion of the band begins to rub or pinch against the end of your femur bone. This friction, which occurs repeatedly when running, eventually leads to soreness in this area.

Like pes anserine bursitis, the pain from IT band syndrome is typically worst as you are exercising or playing your sport and better when you are resting. This soreness may be accompanied by snapping or popping at the knee and occasionally by swelling.

Risk Factors

Depending on the condition, there are several different factors that can increase your likelihood of developing pain on the side of your knee. These include people with:

• A family history of OA
• Diabetes
• Systemic inflammatory disease
• Excess body weight

In addition, participation in sports or exercises that involve cutting, quick changes in direction or speed, or jumping can increase the risk of experiencing other conditions.

These include an acute meniscal tear or a sprain of your MCL or LCL. Likewise, endurance activities like running or cycling can increase your likelihood of experiencing IT band syndrome or pes anserine bursitis.  

Diagnosis

If you are feeling pain on the side of your knee, it is important to speak to your healthcare provider. This is especially true if it occurs after an acute injury or if the pain is not improving with at-home treatment. Typically, your practitioner will conduct a comprehensive evaluation to properly diagnose your condition.

This workup typically involves questions about activities that cause your pain and other symptoms you are experiencing. Issues like IT band syndrome and pes anserine bursitis are usually able to be identified with this process alone.

Treatment

Many of the symptoms that are associated with the knee conditions detailed above can be treated successfully, either at home or with treatments from a medical provider. Some of the most common options are detailed below.

At-Home Treatment

If you experience an acute injury, like a ligament sprain or a meniscal tear, it is important to seek medical attention before attempting to treat yourself. With most conditions, however, there are several initial steps you can take to address your symptoms. These include:

• Icing and elevating your knee: This can help reduce any pain, swelling, or inflammation that is present after an injury or flare-up of pain.
• Wearing a compression sleeve: This may be useful for controlling any swelling that is present.  
• Actively avoiding any pain-causing activities: This plays an important role in reducing your symptoms and is particularly important with overuse conditions, like IT band syndrome or pes anserine bursitis, which can be aggravated by excessive running or jumping.
• Over-the-counter (OTC) pain medications: These may be helpful, though it is best to ask your healthcare provider before you begin taking them.

Medical Treatment

Unfortunately, in some cases, your knee pain cannot be improved with at-home treatments. In these situations, your practitioner may recommend several different options. These can include:

• Physical therapy (PT): This can be useful for improving your leg strength and reducing the pressure placed on an arthritic knee or one with a meniscal tear. PT can also help improve joint stability after a ligament injury or reduce the pain associated with IT band syndrome or pes anserine bursitis by increasing your flexibility.
• Cortisone injection: This helps to reduce the inflammation in your knee.
• Surgery: In some situations, surgery is the only option. For osteoarthritis, this usually means a partial or total knee replacement. In the case of a meniscus injury, arthroscopic surgery is performed to repair the cartilage or to remove the torn portion. Surgeries may also be needed to repair an MCL or LCL tear or (in rare cases) to remove the pes anserine bursa if it is chronically bothersome.

Prevention

When it comes to preventing degenerative conditions like osteoarthritis or a meniscal tear, one of the most important factors is maintaining a healthy body weight.

Other more acute injuries like an MCL or LCL sprain can be more challenging to prevent, however, regularly strengthening your quad, hamstring, and hip muscles can help reduce the chances of one. Working with a physical therapist to improve your overall running and jumping mechanics can also be beneficial.

When trying to avoid IT band syndrome or pes anserine bursitis, focusing on maintaining flexibility in your hamstrings and quadriceps with regular stretching can be useful. It can also be helpful to speak with a physical therapist or personal trainer to help fine-tune your running or biking techniques and to design an appropriate training regimen.

A Word from Verywell

As you can see, there are a wide variety of issues that can cause pain on the inside or outside of your knee. Because of this, it is important to seek medical care for persistent soreness in your joint. Doing so can ensure that a proper diagnosis is made and appropriate treatments are provided. By working hand-in-hand with your healthcare provider, you can get back to the activities you love as quickly as possible!