Knee

Knee Trauma: Knee Contusion

Normal Anatomy

The bones of the knee are the femur (thigh bone), tibia (shin bone) and patella (kneecap). The femur and tibia meet to form the knee joint which is a hinge with the knee cap(patella) in front of these two bones acting as a mobile shield to protect the joint. The patella slides up and down in a groove in the femur called the femoral groove as the knee is bent and straightened.

Ligaments hold the knee together and give it stability. The medial (inner) collateral ligament (MCL) and outer (lateral) collateral ligament (LCL) limit sideways motion of the knee. The posterior and anterior cruciate ligaments (PCL and ACL) limit forward and backward translational motion of the knee bones, keeping them stable and allowing the knee to function as a unit.

Two structures known as menisci sit between the femur and the tibia and act as cushions or shock absorbers for the knee. Menisci are one of two types of cartilage in the knee. The other type, articular cartilage, is a smooth and very slick material that covers the end of the femur, the femoral groove, the top of the tibia and the underside of the patella. This articular cartilage allows the bones to move smoothly without pain. If this layer wears away, it is called arthritis and then the motion becomes painful.

Tendons connect muscles to the bones of the knee. The quadriceps muscles on the front of the thigh are connected to the top of the patella by the quadriceps tendon, which covers the patella and becomes the patellar tendon. The patellar tendon then attaches to the front of the tibia. The hamstring muscles in the back of the leg attach to the leg bone (tibia) at the back of the knee. The quadriceps muscles straighten the knee and the hamstring muscles bend the knee both of which are required for walking, running or simply standing.

Pathology

Trauma is the term used to describe injury. Trauma is classified by its severity depending on the amount of force used to cause the injury. Trauma is also distinguished according to whether it is caused by a single major force or minor repetitive, smaller forces which are cumulative (additive) over time. This is referred to as Cumulative Trauma Disorder (CTD). An injury is also classified depending on if the skin was breached, called an open injury or the skin layer stays intact, referred to as a closed injury. When an injury is minor, it is called a contusion and in this instance, it implies that the injury was closed and only involves the soft tissues including the skin, subcutaneous tissue, muscles, tendons, ligaments, arteries and nerves, alone or in combination. In a contusion, the soft tissue is bruised or stretched, but not torn and requires only symptomatic treatment. The same force of trauma sustained by different patients will result in different injury severity because changes that occur in our body’s internal structure with aging. Specific changes occurring with aging is the amount and type of collagen in our body through metabolism is converted from Type I collagen which is the typical collagen most often found in the human body is converted into Type II collagen. Type II collagen is less resilient and is the type of collagen found in healing scar. The protein, elastin, which gives tissue its stretch properties, also decreases in content with aging. Finally, the water content in the cells of the body decrease with aging. Below is a graph that depicts an identical force sustained by individuals at different ages divided into 20-year increments and the time it takes for each group to heal and become symptom-free. The white section is when the patient is symptom-free and the yellow section is when the patient is having symptoms including pain, stiffness, weakness, and poor function. Note the curve does not come back to baseline and shifts to the right with aging.

Treatment

The most common symptomatic treatment used for all types of soft tissue injuries has three approaches:

1. R.I.C.E. treatment,
2. Anti-inflammatory treatment
3. Controlled early motion and therapy.

The acronym RICE stands for Rest, ice, compression and elevation. Rest is usually done for 24-48 hours, and can include the use of slings, splints or other types of immobilizers unless otherwise advised by a physician. Ice is used for no more than 20-30 minutes at a time, three to four times per day. Ice is best applied by using an ice slush which transmits the effects of the cold sensation best and can be made by crushing ice and mixing it with water and then placing it in a zip lock plastic bag. The ice bag should not be placed in direct contact with the skin but instead should have a layer between the skin and ice bag like a towel to prevent the skin from freezing. The ice should be applied for no more than 20-30 minutes to avoid skin freezing as can occur if you fall asleep with an ice pack on your limb. Ice functions by causing the arteries to narrow the size of their lumen which in turn decreases swelling and the pain from swelling.

Compression is the wrapping of a body part to further assist in minimizing swelling and is used in conjunction with elevation. The best way to do a compressive wrapping is by having the compression have multiple layers that provide a cushion effect. The compression should be wrapped without causing the constriction of the blood supply which is recognized by increasing pain to the body part wrapped. Other signs of a tight compressive dressing are the cold sensation of the wrapped limb, blue discoloration of the body part, or change in color from the natural skin color. Elevation of an injured body part is best done by elevating the limb to the level of the heart. If elevation is lower than this, the effects of gravity on the veins, will increase vein pressure and cause the blood in these veins to have difficulty traveling back to the heart and result in limb swelling.

The use of anti-inflammatory medication helps treat the pain, swelling, and inflammation that occurs after injury is imparted on a limb. Examples of anti-inflammatories includes aspirin products, Ibuprofen (Motrin® and Advil®), Naproxen (Aleve® and Naprosyn®), Mobic®, Indocin®, Arthrotec®, and Celebrex® to name a few. All of these medications have side effects and should be taken with this knowledge in mind. Prescriptions should be discussed with your pharmacist and physician.


Controlled early motion and therapy to the involved limb decreases the effects of prolonged immobilization which includes stiffness, muscle atrophy, weakness and a longer return to the pre-injury state. The type of therapy recommended will depend on the tissue type injured and the severity of this injury. Consult your surgeon for the best advice.