Sometimes patients are rightly concerned about pain on just one side of the knee. In this blog, I will try to sort out the most common causes of pain on the side of your knee.
We can start by talking about which side of the knee is painful. In order to do this, we have to understand a common language so we can accurately describe the location. It is very similar to your smart phone gives you directions. Instead of using North, South, East and West to locate where you are in the world, doctors use the anatomic position to describe where your symptoms are located. The anatomic position is you facing forward with both arms extended and palms up. The front of the body is known as Anterior. The Back part of the body is known as Posterior. If you move up the body toward the head, this is called Proximal. If you move down the body, this is called Distal. Now, the most important location descriptor for your knee will be either the inside or outside of the knee. The inside part of the knee which is the part of the knee closest to your other knee is called Medial. The outer portion of your knee closest to your outstretched hand is calledLateral.
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Lateral (outside of the knee) pain can be caused by: Nerves– Sometimes, the portions of your nerves exiting your spine can be irritated and end up causing pain down your sciatic nerve to the outer portion of your knee. You may say “hey how can this be since my back does not hurt?” and I would say…”Hey, this is a great question.” There are two branches of the nerves coming out of your back. The smaller branch exits the spine and enters into the joints and muscles around your back. When this branch is pinched, you will have “back pain.” However, a majority of the time, just the larger branch of the nerve exiting into your leg, buttock or thigh is pinched giving you the feeling of pain in the area where the nerve innervates (which means ends up). This is known as referred pain and is confusing for some patients to understand. If you have nerve pain, it is usually burning and radiating meaning it seems to move up or down the leg. It is normally worse with positions such as prolonged sitting in your car or even when you lay down at night since this seems to place more stress on the discs in your back. Most people with nerve problems can remember other events where they may have had “sciatica” or “lumbago” since this is a chronic problem which seems to worsen with time and age.
Tendons– The outer part of your knee has some very important tendons which help stabilize your knee and even your pelvis. The most common tendon to be inflamed is the Illio-tibial band otherwise known as the IT band. This becomes irritated with repetitive motions such as running and thus as the nickname “Runners Knee“. This tendon runs up the outer portion of your knee all the way to your pelvis. People sometimes complain of a dull ache which is occasionally sharp after activities such as running or cross country skiing. However, you do not need to be a runner or skier to experience this problem. Again, if you have a nerve problem, this can cause chronic weakness of the muscles in your leg leading to overloading of the tendons. Muscles– If some specific muscles around your knee are affected, you may experience pain. The mot common is actually weakness to a muscle on the inside (medial) part of your knee called the vastus medialis oblique muscle which attaches to the medial side of your knee cap. When this becomes weak, it will cause the knee cap to start to move lateral and rub over the outer part of the knee cap. The knee cap can even tilt and rub more causing scaring and a chronic condition sometimes referred to as lateral patellar compression syndrome. This pain is normally dull but can have periods of sharp pain when the knee cap tries to move out of it’s normal groove. The symptoms are worsened when there is excessive and prolonged pressure on the knee cap such as sitting with the knee bent for long periods (theater knee) or with squatting, kneeling or lunges. Bursae- A bursa is a sack of fluid which is designed to allow tendons to glide over bones, muscles or other tendons. Sometimes, these sacks become inflamed and we add the ending “itis” to the bursa to give it the name bursitis. Patients with bursitis normally talk about a dull ache over the side of their knee which is worse with activity and better with rest. Some patients report a rubbing feeling.
Joint- Inflammation of your knee joint is technically known as arthritis. When this joint becomes inflamed, it can cause pain all over the entire joint or sometimes, just where the arthritis is most advanced. This is especially true if you are knock kneed meaning your knee makes an angle outward from the center of your body. Arthritis pain is again a dull ache and occasionally sharp with activity and better with rest. Meniscus – When the stabilizing and shock absorbing rings of your knee are torn, they can cause pain and most importantly instability of the knee. A meniscus is a simple “c” shaped cartilage type washer in your knee desinged to help stabilize the knee during motion. There are two of these. The one on your outside is called the lateral and the one on the inside is called the medial. You do not need to have trauma to your knee to cause a meniscus tear. In fact, most tears are due to aging of the meniscus. When the meniscus tears, it becomes caught between the two bones of your knee especially during twisting motions of the knee and a sharp pain happens sometimes causing your knee to buckle or catch. Most patients with a meniscus tear will have a sharp pain to the knee usually when descending stairs or a downhill slope.Sometimes, these symptoms are followed by some mild to moderate swelling and continued dull ache. In some patients, the symptoms will subside for weeks and months at a time but most return to become a chronic problem.
Medial (Inside) knee problems include mainly some of the same problems as lateral with the following exceptions. Ligaments– The medial collateral ligament (MCL) is more commonly sprained than the lateral collateral. This can be caused by a simple strain to the knee such as when stepping too harshly from a ladder or stool. However, it can also be associated with repetitive stress to the ligament such as walking sideways on an incline or even simple sports such as bowling. The pain is usually acute and can sometimes be associated with a pop to the knee. The pain is usually sharp and radiates a short distance to the upper (proximal) part of your shin bone (tibia). The pain is worse with weight bearing especially with side to side movements. This pain can also be present for months at a time because it is difficult to heal due to constant stress across this ligament with normal activity. Unfortunately, the medial collateral ligament has an attachment to the medial meniscus and it is very common to find both a ligament and medial meniscus problem together. Bursae– The most common bursitis of the knee in maturing patients seems to be on the medial side of the knee over an area called the pes anserine bursitis. This is a literal Latin translation of a duck’s foot bursitis because the three tendons attaching to a common complex over the medial side of your knee resembles a small duck’s foot under your skin. Don’t worry, this will not quack like a duck but, it will hurt like a duck pecking at the inside part of your knee. The pain is normally a dull ache, sometimes sharp. It is worse when the two knees touch together such as when you are sleeping on your side at night. Many patients sleep with a pillow between their knees to prevent this pain. Nerve pain– Nerves from your hip joint and your back as well as through a tunnel of muscles near the inside part of your thigh can also cause pain to the medial side of the knee. Referred pain from an arthritic hip joint is the most common. A branch of the obturator nerve from your pelvis runs over near the top of your hip joint near your groin. When this is irritated, you will notice pain to the anterior and medial part of your knee. This is normally worse with activities which irritate the hip joint such as placing on your shoes or socks or getting out of a chair or car. Joint– Arthritis pain on the medial side of the knee is a very common cause of pain especially if you are bow legged (where your knee angles away from the middle). Again, this pain is dull and aching, occasionally sharp. It is worse with activity such as walking and better with some rest.
Now that you understand the most common causes of pain to the side of your knees, you can help your doctor make an accurate diagnosis so the both of you can come up with an appropriate treatment plan. Hopefully, this blog has helped you understand the language barrier between patients and physicians. Our goal is to work with you in obtaining good health and understanding the language is the first step in this process.