Know the Knee, Fix the Knee
There is a ton of great resources out there about knee pain and how to fix it, but what about how we think about the knee? In my opinion, we have to see the knee differently in order to get at the cause of knee pain before we start talking about how to fix it. This article takes a stab at how modern Physical Therapists see nagging knee pain before making a plan to treat the knee.
I start with the type or nature of knee pain, cover the anatomy and function of the joint, then give my take on the knee as the “dumb” joint, and how the hip and ankle are where we see the knee issues.
Types of Knee Pain
Knee Pain comes in many forms, namely: trauma, post-operatively, acute (sudden), and chronic. The causes of knee pain are diverse and vary dramatically based on personal characteristics such as age, activity level, and history.
However, one thing is for certain, everybody with nagging knee pain is sick of it! It impacts your performance, is a constant reminder that something is wrong, and can be difficult to diagnose. So here we provide an outline for finding the cause of recurrent and nagging knee pain, how to develop a plan of attack to relieve it, and what to do to keep it away.
A surface review of anatomy tells the 4 things we need to know about the knee:
It is connected to the “hip bone” - the femur is the connection between the knee and hip.
It is connected to the “ankle bone” - the tibia is the connection between the knee and ankle.
The knee moves primarily in a single plane of motion. Another way to say this is that, while it does rotate and tilt, more than 90% of it’s motion comes from bending and straightening (flexing and extending).
10 muscles cross the knee (11 if you count the gluteus maximus attachment to the ITBand). 7 (or 8) of these cross another joint - namely the hip and ankle.
Function of the Knee
The Knee is more complex than it seems. It plays a significant role in shock absorption and force control, as well as generating force to move - like waking, running, or jumping. It is designed to bend and straighten quickly and without limitation. It is supported by 4 ligaments as the “scaffolding” that give the joint it’s structure since it is not completely surrounded by bone like the hip joint. The ACL is one of the 4 ligaments that is intended to assist in controlling or stopping force from disrupting the knee.
The Knee is the “Dumb” Joint
I like to say this to patients a lot. Sometimes it makes sense and other times, it sounds like a punch-line to a bad joke. Here is what I mean - the knee moves primarily in 1 plane of motion and is forced to take the stress from the joint above (hip) and below (ankle). It sits there and takes a beating without having a mind of its own to control it’s fate. I don’t mean that the knee is not important - it’s very important. However, recognize that control is about force production - and the knee has limited resources when it comes to control, because most of the muscles that cross the knee are in combination with another joint. Also, the knee is surrounded by ligaments, which I like to think of as scaffolding. It gets caught in the crossfire of the ankle and hip, while trying it’s best to absorb force coming from all directions.
Knee Injury is usually not caused by the knee
Huh? I know what you’re thinking - this article is now making less sense that ever. Stick with me and maybe there will be a few points in here that resonate. And trust me - any good Physical Therapist, Doctor, Chiropractor, Massage Therapist, Acupunturist, etc are taking this same approach.
When treating chronic or nagging knee pain, it is critical to turn your focus away from the knee. (Of course, trauma and post-operative knee pain is a whole different story.) If we consider the knee as “the dumb joint” that doesn’t control it’s own fate, it seems obvious that we have to look elsewhere for a culprit, right? So where do we go?
Up the Chain
The hip is a multi-directional ball and socket joint that generates a lot of force and is the point in our body where two becomes one (two legs to one pelvis/core). Here, the potential issues that are causing knee pain that the physical therapist is looking for are:
Mobility deficits in rotation - primarily internal rotation. If you lack internal rotation of the femur at the hip, you may experience more torsion at the knee. When the foot its the ground during running/jumping/etc, it collapses and the shin rotates in. If the femur stays out, we’ve got problems.
Lack of hip extension - if the hip can’t get behind you, the knee either has to hyperextend during gait or it never gets straight. Both of these are problems for different reasons. Hip flexor tightness or over-activity of the hip flexors will often impede your ability to gain full hip extension.
Hip backside weakness - we call this posterior chain weakness and we are talking about the glutes and hamstrings. These muscles need to be the primary generators of force and stabilizers of rotation when you move. Try and argue that.
Down the Chain
The ankle, also multi-directional, is extremely complex. The intricacies of the ankle are too much for this article, so we will have a few follow-ups on this. For now, know that the ankle must take a shape that ensures good balance while also being the first line of defense in controlling force. The ankle issues that can lead to knee pain are typically:
Poor heel control - most people call it a “pronated” foot and that is mostly right. Usually, the heel is tilting too far and the arch falls too far - resulting in shin rotation in that is too fast to handle when we use force - like running. This can either be just the foot god gave you, or a strength issue that needs correcting.
Limited ankle dorsiflexion - the shin has to move forward for the knee to bend with your weight over your foot. If the knee bends and the ankle doesn’t bend, that’s bad mechanics and issues happen. Could be calf tightness, joint restriction, or abnormal motor patterning.