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Knee Pain
Continuation of the series “Aches and
Pains We Can Afford to Live Without”
By Dr. Achutha Menon, MD, M.Ch.Orth., F.R.C.S., F.R.C.S.Ed

Although the knee joint may look like a simple joint, it is one of the most complex in the human musculo-skeletal system. Moreover, the knee is more likely to be injured than is any other joint in the body. We tend to ignore our knees until something happens to them that causes pain. As the saying goes, however, “an ounce of prevention is worth a pound of cure.”
            If we take good care of our knees now, before there is a problem, we can really help ourselves. In addition, if some problems with the knees develop, an exercise program can be extremely beneficial.
            The knee joint is made up of four bones, attached to one another by four main ligaments for stability, and supported and surrounded by four muscles for mobility. Movements at the knee are often thought of only as “bending” (flexing) and “straightening” (extending). However, that is not the whole truth. A very important component of knee motion is “rotation,” referred to as “the screw home” movement. Interference or interruption of this rotary component is one of the main causes for knee injury that often goes unrecognized.
            Any joint is so structured as to provide mobility as well as stability, and depending on the location of the joint, mobility or stability may be the dominant functionality of that joint. Generally speaking, joints of the upper limbs have more mobility than stability, whereas joints in the lower limbs have more stability than mobility; the purpose of such a provision is apparent in that the upper limbs are used for non-weight-bearing movements, whereas the lower limbs are used for weight-bearing movements. The knee joint, for a joint in the lower extremities, shows a surprisingly wide range and variety of motion, and this makes it vulnerable to injury and insult, much more than any other single joint. To illustrate with an example – one can use one’s hands “to give” (in the prone position of the forearm with the back of the hands up) or “to take” (in the supine position of the forearm with the palms facing up). The prone position of the forearm is more comfortable and functional, than the supine position, because … “Life is to Give and not to Take.” Similarly, the foot can be used for standing and walking (to take body weight and to progress) or for kicking (to throw body weight around – as in kick-boxing for example) and running; running can injure the knee joint, whereas kicking will add insult to injury.
            The four bones that constitute the knee joint are (1) the Femur (thighbone), (2) the Patella (kneecap), (3) the Tibia (the shin bone) and (4) the Fibula (a thin bone that runs parallel to the shin bone on its outside). The Fibula does not actually participate in the articulation, but offers important and substantial perch to some of the ligaments and muscles of the joint, so that its upper end is expanded; compared to its slim shaft, it has a big head. So, essentially the knee joint is the articulation or meeting point between the lower end of the thigh bone (Femur) and the upper end of the leg bone (Tibia), with the Kneecap (Patella), as it were, holding a cloud of protection over the articulation, to contain the congruity during movement. Congruity of the articular or contacting components, in the case of the knee joint the lower end of the Femur and the upper end of the Tibia, or in other words, how well the two ends are suited to each other to form a joint (as in a ball and socket joint) is as important for joint stability and safety as for a nuptial couple. And the lower end of the Femur and the upper end of the Tibia are least suited to each other; the lower end of the Femur is rounded and irregularly ovoid, whereas the upper end of the Tibia is flat! This is an instance where stability has been compromised for mobility because of all the joints in the lower limbs it is at the knee that maximum movements take place while walking, running or kicking. There are, of course, a couple of structures called the “cartilages” or “Menisci”, which add some depth and shape to the flat upper surface of the tibia, but at best such arrangement is only a pretension for perfection.
            The one guardian of this incongruous joint is the Patella (Kneecap), with the powerful Quadriceps Muscle, attached above extensively to the shaft of the Femur and the tough Patellar Ligament attached below to the Tibial Tubercle (a knob-like prominence on a bone.) This attachment from the Femur to the Tibia, with the Patella inside it (and described as a Sesamoid Bone in the Tendon of the Quadriceps) not only keeps the two bones nested against each other, but also enables controlled movement, as if with reins. It is impossible to overstate the ability of this mechanism to obtain stability during mobility. No wonder the Quadriceps (the muscle group in front of the thigh, four in number,) is called “The Guardian” of the Knee joint; they subscribe heavily to the shape, size, strength, stability, and style of movement of the whole lower limb.
            The Muscles behind the knee (also four in number), i.e. the three Hamstrings and the lateral head of the Gastrocnemius (Calf Muscle) actively bend the knee, and passively “pay out rope” or allow slack to the Quadriceps during straightening of the knee. These muscles extend from the hip bone to the heel bone and play an important roll in the co-ordination of the movements of the foot, knee, and hip, in such activities as walking, running and jumping.
            It is even more prodigious to contemplate how this “Quadriceps Mechanism” functions during daily activities. A muscle, Quadriceps in the present instance, is said to have an “origin” (for Quadriceps it is the shaft of Femur, or thigh bone), and an “insertion” (the Tibial Tubercle for Quadriceps), and the muscle is supposed to act from its “origin” to its “insertion”; the ‘origin’ is the “fixed” point and the “insertion” is the “moving” point.
            Let us consider for a moment what happens during normal walking. There are moments when the Tibia moves under the Femur, as in the “Swing Phase” of walking, and there are moments when the Femur moves over the Tibia, as in the “Stance Phase” of walking. The “Swing Phase” of walking is that phase during which the foot moves from one step to the next, whilst the other foot remains fixed to the ground, and the “Stance Phase” is when the foot remains fixed to the ground and the upper leg (thigh – Femur) moves forward on the fixed lower leg (Tibia), whilst the other foot moves forward from one step to the next. It is worth noting that during the “Swing Phase,” the Quadriceps acts from its Origin (the Femur,) to its insertion (Tibia), and during the “Stance Phase” the Quadriceps acts from its Insertion (Tibia) to its Origin (Femur) Apart from these hinged motions during the two “Phases” of walking there is also a rotary motion of the Tibia under the femur and the Femur over the Tibia, the so-called “Screw Home Movements,” so named because the movement “screws the knee joint tight” in its straight position (Extension), so that the leg can act as a strong straight prop for weight bearing, and “unscrews the knee joint” for the movement of propulsion.   And for this anterior (Quadriceps) mechanism to function properly, it has to have the supple support and service of the posterior (Hamstrings) mechanism, as well the stabilizing strength of the joint capsule and ligaments, and the friction free state of the articular and intra-articular cartilages. The Ilio-Tibial Band (a muscle connecting the pelvis to the tibia) with the Tensor (another muscle) pulling it tight while walking, substantially helps maintain the medio-lateral (side-to-side) stability of the joint. The complexity (or perhaps the perplexity) of these movers as well as the movements demands a coordination, the Philharmonic Orchestra may well envy.   It is, then, small surprise how vulnerable the whole mechanism is to injury, inappropriate use, and indigent infirmities.
“Knee Pain” is more often discussed from a ‘causal’ (etiological) approach, i.e. based on what causes it, so that the discussion affords access to the management or treatment. In the following paragraphs, ‘Knee Pain’ is discussed from the ‘age and activity’ perspective, based on the hope that, although one has little or no control over one’s age, one has a tremendous amount of control over one’s activity, and the prime purpose of this article is to discuss prevention rather than cure. So, “Knee Pain” may be classified as occurring in
1.            “The young and the Restless”
2.            “The Adolescent and the Athletic”
3.            “The Adult and the Working”
4.            “The Aging and the Infirm”

This is the first of a multi-part article on Knee Pain. Part II will appear next month.

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