The knee joint is such a cool structure. I especially admire it for it's intricate design.
Let's start with some anatomy. If this doesn't interest you, skip this paragraph. The femur (thigh bone) is connected to the tibia (shin bone) with two rings of cartilage in between to act as buffers, called the medial and lateral meniscus. The menisci move as our knee bends and straightens to ensure a smooth transition. The knee joint is reinforced by various scaffolding including a ton of muscles and a few ligaments. Ligaments that support the inside of the joint are the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL). Ligaments that give support to the outside of the joint are the medial collateral ligament (MCL) and the lateral collateral ligament (LCL). The knee cap in front is called the patella and it helps create a pulley system between the quadruped muscles and the tibia. There is another lower leg bone neighboring the tibia called the fibula, which helps support the knee by being an anchoring point for the LCL and Iliotibial Band (IT Band). It also allows our lower leg and ankle more options for movement. Although considered a "hinge" joint, when the knee bends and straightens, the femur and tibia (with the fibula) actually rotate very slightly, an action that is called the Screw Home mechanism. This is made possible because the two menisci are shaped slightly differently from one another. The knee is lubricated by synovial fluid, which bathes the joint during movement, and is protected from friction by bursa sacs and plica.
Okay, phew, that was a brief anatomy lesson that only brushes the surface of what's involved in this joint! That's because I wanted to get to the most interesting thing about the knee: it's the monkey in the middle between two other very mobile joints, the hip and the ankle. Yes, we could take this more globally to include anything else in the body that potentially affects the knee, like the pelvis, ribcage, neck, and shoulders, oh my! But let's keep this discussion relatively local for now. Ah...the poor knee. It tries to do its very best only to be thwarted by dysfunction from above and/or below.
With the hip and ankle nearby and their potential for error, the knee is often just another domino in line of consequences. With overuse of some muscles while underuse of others, the knee can receive asymmetrical stress and strain. Above the knee, we have the hip. The hip is a ball-and-socket joint so there are many more options of movement than the knee's hinge joint. If there is not enough movement in the hip or if there is hip weakness, the effect can trickle down the appendage chain. There are many research articles showing that when we strengthen the hip, we improve patellofemoral pain syndrome (1,2). Below the knee, we have the ankle and foot. The ankle joint has a little bone called the talus that tracks between the medial and lateral malleolus (those knobs we have on either side of the ankle). The foot has many tiny bones with tiny joints between them. Because of both of their anatomy, there are great opportunities for movement or lack thereof. If there has been an ankle sprain or a good jam of the big toe, the ankle and foot start moving differently. Each step walking forward introduces a different strategy of movement throughout the leg than what was used before the injury.
The knee itself could be dysfunctional on its own but I find that clinically, this is a rare scenario. If there has been trauma to the knee, or there is general hypermobility throughout the body, or if the knee joint demonstrates disease states such as significant osteoarthritis (OA) or rheumatoid arthritis (RA), the integrity of the knee can certainly be compromised. With OA and RA, the lifestyle choices of the individual should be the first line of defense. Chronic inflammatory states that come with a poor diet (such as sugar, alcohol, smoking), poor sleep quality, chronic stress, and minimal exercise lead to all sorts of signs and symptoms. This can create a systemic cascade of reactions, including knee joint issues. For these folks, knee pain can be only one item on the list of many bodily systems that are suffering.
What makes me cringe is when people go to the doctor for knee pain and the only area observed is...the knee! But what about all these other nearby areas that feed into the knee? I don't blame the doctors that have 10 minutes to make a clinical decision. I blame the medical model of stuffing as many patients as possible into their workday. Usually, the doctor will first offer an x-ray. If insurance will cover it, which they most likely won't, I propose to request that both knees are x-rayed to compare the two. If you are any age above your mid-twenties, you will have OA in both of your knees. Is this the worst news ever? Absolutely not! Just as our hair and our skin change as we age, our insides change too. It would be un-human to have no OA in your knees. Be curious if you are diagnosed with OA in one knee (without ever seeing the other) and don't be convinced that this is the sole cause of your pain since this is typical aging. The orthopedist may even offer a corticosteroid injection for pain relief. Please do your research with this, starting here! Mind you, this article was written in 2017, so this is something that the medical community is well-aware of but continues to offer to patients. Who wants to speed up cartilage degeneration?! It's the fast track to a knee replacement. Sure, you might have short-term relief but the long-term risk is frightening and NOT WORTH IT.
So what are you to do if you or someone you know suffers from knee pain? Go somewhere that looks at the forest for the trees. The knee is rarely acting alone unless there is a systemic disease state. How are neighboring areas moving? Where are areas that are working overtime and others that are taking a snooze? What are your movement strategies for things you do every day like walking, going up/down the stairs, and squatting? Advocate for physical therapy with your doctor and go to a therapist who will find out what YOU need, not what general-patients-with-knee-pain need. If you're not having luck with relief, the driver of your symptoms may not have been addressed just yet. Keep asking why.