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Biology 103
2005 Final Paper
On Serendip

The biology of a sprain

Stephanie Hunt

I have recently had the frustrating experience of spraining my ankle. I understood the ideas of R.I.C.E.—rest, ice, compression, elevation—and I understood that my ankle hurt, was swollen for weeks, had bruises in places that had not made direct contact with the rock that I slipped on and worst of all, I understood that my ankle was weak and kept causing me to fall unexpectedly on it. But I did not understand why R.I.C.E. was supposed to help my ankle get better, what was causing the prolonged swelling and bruising or what specifically was weakened and causing me to fall and re-injure it every week. Researching this topic was moderately frustrating: there are a lot of medical website that "dumb down" the information to a point where I probably could have written based on my own first aid knowledge and there are a few, more helpful, medical websites that sent me on dictionary treasure hunts every word. I hope to be able to shed some light on the physiological processes that occur during a sprain.

There are two types of common ankle injuries that can lead to sprains. One is when the ankle rolls outward and the foot rolls inward, called an inversion injury. This is an injury to the lateral ligaments, which are the anterior talo-fibular ligament, the calcaneo-fibular ligament and the posterior talo-fibular ligament (2). The other, which is far less common, is when the ankle rolls inward and the foot outward, called an eversion injury, an injury to the medial ligaments (1) or the deltoid ligament complex (2). Ligaments are made up of collagen tissue (3), which is also the type of tissue that makes up skin and bones (10). Sprains result when the ligaments are stretched farther than they normally would. This overstretching may result in tearing the ligament partially or completely (2).

Ankle sprains are divided into three categories, depending on their severity. A Grade I sprain is the least severe; no instability results and although there might be microscopic damage to the ligament, no tearing occurs. In a Grade II sprain, the ligaments may be partially torn, but no significant instability results from the sprain. A Grade III sprain is the most severe; the ligament is torn and there is significant resulting instability. The most severely damaged (and most commonly damaged) ligament is the anterior talo-fibular ligament, while the least common and least severely damaged ligament is the posterior talo-fibular ligament (2). In order to test to see if the ligaments are completely torn, doctors may perform a stress test in which they put posteriorly-directed force on the tibia. If the anterior talo-fibular ligament is torn completely, the tibia will visibly shift backward at the ankle and will snap back when force is removed (2). A complete tear may result in the need for surgery, but surgery is not recommended or useful in most cases of sprained ankles (3). There is controversy over whether or not a person with a sprained ankle should have surgery. Studies show that surgery should only be done if there is evidence of a complete tear of a ligament (8). It is also possible for the ligament to be torn from away from the bone. This is known as avulsion. Walking would be impossible with this type of injury (6).

Not long after the injury, the ankle begins to swell up. Bruising may be more prolonged and may not occur in minor injuries at all (3). Bruising can be caused by damaged blood vessels from the impact, but can also indicate that a ligament is torn (5). I think that there could be other reasons that there is bruising as well. Perhaps blood rushes to the area in order to help with healing and then is stuck there. Fibrosis also tends to occur following a sprain (3). Fibrosis is the formation of excessive fibrous tissue as a reparative or reactive process. This causes swelling in the area of the injury. Also contributing to the swelling around the area of the injury is serous fluid released from the torn tissues of the ligament (4). I had to look up what "serous fluid" was in the dictionary and found that serum can either refer to watery fluid that is found in animal tissue or to a yellowish fluid found upon separating clotted blood. I could not find information about which serum accumulates following an ankle sprain. It would make sense for it to be related to blood clotting as there is typically bruising with an ankle injury, but the type in edema is the watery type of serum. This swelling could be constricting the blood flow as well, which may contribute to the bruising.

Immediately after an ankle injury, it is necessary to keep moving the ankle. The reason for this is that edema tends to stiffen into a slightly flexed, inverted position (4). I tried to find information about why it stiffens into a particular position, but had no luck. I assume that it is because of the position of the ligaments when they are loose. If this stiffening of the edema occurs, then rehabilitation will have to be put off until a better range of motion is regained (4). Most children are taught in elementary school health class that injuries require rest, ice, compression and elevation. Rest in the case of an ankle injury helps to prevent further injury from direct contact with the ground while walking. Icing is important because it helps to reduce the swelling of the injured area. The optimal temperature for cooling the ankle is about 55 degrees Fahrenheit and should be done every few hours until the swelling and edema, or excessive accumulation of serous fluid, have stabilized (4). (I discovered while looking up "edema" that plants can also have edema, accumulation of water in their organs, as well as people. This makes me wonder if plants can be "injured" in a similar way to humans.) Compression helps to milk edema fluid away from the injured tissue, reducing swelling (4). Also, reducing the edema will prevent it from stiffening and causing a delay in rehabilitiation. A compression wrap can help to milk away the edema while also holding the ankle in place to prevent further injuries (1). Elevation of six to ten inches above the heart aids in venous and lymphatic drainage (4). This implies to me that the elevation is not actually reducing the swelling so much as aiding circulation while the swelling is constricting the blood flow through the veins.

In addition to the common treatment of R.I.C.E, there are some alternative treatments that may be effective for a sprained ankle. If the sprain is very severe, it might be helpful to raise calorie and protein intake to accommodate for the needs of the healing processes, but this is not recommended for most sprains (6). Also, a person with a sprained ankle might take proteolytic enzymes in order to reduce in the inflammation as well as to promote tissue healing. There is controversy over whether or not this actually works, as some trials found that healing was faster in people taking these enzymes than in people who were not, while other trials found that there was no significant effect (9). Another alternative remedy is horse chestnut as it contains aescin, which is an anti-inflammatory that also helps to reduce edema (9).

About 25% of people that sprain their ankle have long-term joint pain and weakness. The joint will become unstable if it does not heal correctly and will be easily reinjured (1). A common medical mistake is to immobilize the ankle too much or for too long a period of time (4). This makes sense because immobilization does not allow for any strengthening of the ligaments that are injured. The collagen fibers heal the fastest and orientate along the lines of force when supported mobility occurs (3). This is why doctors suggest using a brace that allows mobility after a sprain.

Complications other than the usual symptoms may also arise from ankle sprains. The meniscoid body is a small capsule that can get pinched between bones in the ankle, resulting in synovitis. Synovitis is the swelling of the membrane around this capsule and causes persistent swelling and pain. Eventually, this can become permanent, but it can be treated with injected corticosteroids. Inversion injuries can result in damage to the superficial peroneal nerve that crosses over the anterior talo-fibular ligament. Another complication of an ankle sprain may be reflex sympathetic dystrophy, which is painful swelling related to osteoporosis or a sudden constriction of blood vessels (angiospasm) secondary to the initial sprain. The edema is different from that of the torn ligaments and the relevant symptom is pain with multiple trigger points from one site to another. There may also be changes in skin moisture and coloration. A more mysterious complication is sinus tarsi syndrome, which is simply chronic pain in the area of the sinus tarsi. People are often misdiagnosed as having this because the anterior talo-fibular ligament crosses over the sinus tarsi and it is difficult to distinguish the exact point of pain. Thus, it is important for the doctor to examine both ankles in order to compare tenderness. Sinus tarsi syndrome can be treated with an injection (7). Another, seemingly newer finding is that anterolateral impingement lesions coexist with chronic lateral ankle sprain. It is believed that recurrent inversion stress is the cause of both the chronic instability as well as the lesions (8).

I can now make sense of the healing process that is occurring in my ankle and why it was so important for me to apply ice and compression to my ankle in the days after I sprained my ankle. I was surprised to find little in the way of concise biological information about sprains, torn ligaments or even R.I.C.E. on the internet. As I said before, websites seemed to be either too simplified, including little information regarding the underlying biological aspects of a sprain, or they were too difficult for an ordinary reader (like myself) to understand. Hopefully, in sharing my findings with the world, someone will be able to benefit from have biological and medical information integrated in a way that is understandable.

Web Sources
(1)Applying a compression wrap for a sprained ankle.
(2)Ankle sprains.
(3)Acute ankle sprains.
(4)Management of ankle sprains.
(5)AllRefer Health: Ankle Sprain Swelling.
(6) Sprains and Strains
(7)The Merck Manual: Common foot and ankle disorders
(8)Lateral Ankle Instability.
(9)Numark Pharmacists: Sprains and Strains
(10)Extracellular Matrix.

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