by
Chris Linson, PT
Your foot bone’s connected to your ankle bone.
Your ankle bone’s connected to your leg bone.
Your leg bone’s connected to your thigh bone.
Your thigh bone’s connected to your hip bone.
Your hip bone’s connected to your back bone.
Your back bone’s connected to your shoulder bone.
Your shoulder bone’s connected to your neck bone.
Your neck bone’s connected to your head bone.
This children’s rhyme has significant clinical relevance for the field of physical therapy. Yes, of course all your body parts are connected to one another. More importantly, however, movement at any single joint will affect (for better or for worse), the joints above and below it. Indeed, such effects can travel far up and down the body, on the same side, or even to the opposite side. This interconnectivity is why a stiff big toe can give you hip pain; it is why an injured shoulder can give you back pain when you run; it is why knee pain may ultimately have very little to do with your knee joint or the associated muscles, tendons, and ligaments.
The goal of this article is to convey a sense of the biomechanical complexity of the lower extremity (which includes the pelvis, hip, knee, ankle, and foot). A detailed discussion of the entire lower extremity would span several textbooks. After reading this article, however, hopefully the reader will begin to grasp the difficulties in evaluating and treating injuries, but importantly you will start to “think outside the box” in relationship to your own body, how you respond to injuries, and how you think about preventing them.
In physical therapy, we treat a wide variety of musculoskeletal problems, including sprains, fractures, recovery from orthopedic surgery, congenital mal-alignments (e.g., scoliosis), postural tendencies, muscle imbalances, neurological conditions, etc. Note that most of these conditions can be both causes and effects of one another. For example, a muscle imbalance in your calf can make you more prone to ankle sprains; conversely, chronic ankle sprains can alter your gait pattern and set you up for a host of other problems, including low back pain.
For each of these conditions, and the countless others that physical therapists address, we must look how far up and down the kinetic chain to address both underlying causes and resulting effects.
The Kinetic Chain
What is a “kinetic chain”? Simply put, it refers to a series of connected movements that work together. For example, although the foot can theoretically operate independently of the segments above it, in most cases, the hip and knee are essential to facilitating (or controlling) its motion. Similarly, the motion, alignment, and control of the knee is largely driven by the foot/ankle and hip joints. Note that this “chain” continues up the body, for spinal movements can have a significant effect on the lower extremities, and vice versa.
The lower extremity contains a series of very different joints, each of which has profoundly different capabilities as compared to the ones above and below it. At the top, the hip is a ball and socket joint, with many directions of motion. You can move your hip forward and back, you can swing it inward and out to the side, and you can rotate it in and out. Moving down the chain, the knee is a hinge joint that moves primarily forward and back (technically, the joint does move in/out and rotate it, but you generally cannot control these motions). The ankle mostly bends up and down. The foot joints (and there are many of them) move in a wide variety of directions. The toes generally move up and down.
Importantly, each of these joints can (and must) affect all of the other joints of the lower extremity.
Let’s see how this works. Take your shoes and socks off. Stand comfortably and look at the arch of your right foot. Now tightly clench your buttocks together. See how the arch rises a bit, and your foot rolls out slightly. Now try to flatten your arch. See how your knee tries to bend inward—which it cannot do, which in turn should make your
upper thigh roll inward. Now try walking with your arms tightly crossed—see how it affects your hip and leg motions as compared to normal walking.
Why is this relevant?
So the leg is quite complicated. Who cares?
Simply put, this complexity drives the physical therapist’s examination, the subsequent treatment/rehabilitation, and how we approach injury prevention. It’s why just doing knee exercises may not be sufficient to treat knee pain; it is why you might be given lumbar/abdominal exercises for an ankle problem.
Examination and the Kinetic Chain
When we examine a patient with any lower extremity problem, we look at the entire limb. We assess each segment, looking at range of motion and flexibility, muscle strength, motor control and stability. We look at all the systems involved: the muscles, the joints, the connective tissues (tendons, ligaments, fascia), the motor nerves that control the muscles, the sensory nerves that provide critical input to the brain (which in turn controls the muscles).
Then we look more globally. What is the more distant effect of any soft tissue or joint limitations? If hip rotation is limited, does this help explain why the ankle is not moving properly during walking? If the quadriceps (the front thigh muscles) are weak, does this relate to the ankle pain during running?
How does the limb work as a unit? When the patient stands and does a single leg squat, are each of the segments working normally and in synchrony? As the patient walks, how do each of the segments work in relation to the other? If the ankle is stiff, is the hip compensating in a way that explains why the low back hurts?
Often, this portion of the examination is quite difficult, for with a long-standing problem, the initial, underlying injury may have caused other compensatory problems, which in turn may have induced other segments to be involved. In some cases, the original injury has long since healed, and all we see is resulting compensations and/or secondary injuries.
The results of this integrated assessment will help us determine the appropriate treatment approach. It is not uncommon, for example, for us to provide hip stretches and ankle strengthening programs for chronic knee pain.
Yes, we will still provide symptomatic relief for the knee pain. But our goal will be to address the underlying biomechanical factors that caused the knee pain (as well as any other compensatory problems that may have stemmed from how your pain may have altered how you move). Simply stretching the knee, using ultrasound, or icing the sore tissues may all help to briefly alleviate your discomfort, but what provides long-term relief (and what sets apart the better physical therapists) is understanding and addressing how the entire limb functions to contribute to the condition that is being treated.
Injury Prevention and the Kinetic Chain
How will this information help you in the long run? Long after you have recovered from your injury (and more so if your injury leaves you with some level of disability), you will have to treat the entire limb as a unit, instead of solely thinking about the injured portion. This means that to avoid re-injury, you will need to continue to focus on the strength, flexibility, and control of each of the segments of the chain.
When you are developing your post-injury exercise program (which we will help you to do), you will need to think about each of the portions of the lower extremity kinetic chain. For example, if you have a history of knee pain, you will need to exercise your hip and ankle along with your knee.
Regardless of the injury, you will need to keep the entire limb stretched out and limber. You need to incorporate balance and coordination exercises that challenge the entire limb, that force it to work as an integrated unit. You will need to strengthen all of the muscles of the limb.
At SOL PT, we work hard with you to provide an in-depth understanding of how your body works. The holistic, multi-system approach we use will help you to recover more quickly and completely, and more importantly will help you to get better in tune with your body.