Knee injuries

Knee injuries

What is Knee Injuries and Definition

Knee injuries - Sprains, strains, CARTILAGE tears, and fractures involving the structures of the knee. The knee is a hinge JOINT that allows the leg to flex (bend back) and straighten, essential actions of walking. Unique among hinge joints in the body, the knee also allows a small amount of rotation. The knee is vulnerable to both traumatic and repetition injuries. Knee injury is the leading reason for visits to orthopedic surgeons in the United States.

The knee primarily joins the femur (thigh BONE) to the tibia (shin bone) and the fibula (small long bone behind the tibia). It also contains the patella (kneecap), a small bone that provides added leverage for movement of the lower leg. A C-shaped thick pad of cartilage, the meniscus, cushions the ends of the bones from each other. Each knee contains two menisci: the medial meniscus, which wraps around the inside of tibia, and the lateral meniscus, which wraps around the outside of the tibia. Strong ligaments bind the knee from each side and the center, holding the bones in place.

The most damaging traumatic injuries to the knee are those that result from a blow or fall that rapidly stretches the ligaments and causes them to tear (ligament sprain). Sudden twisting motions in which the foot plants but the rest of the leg continues to move also expose the knee to such injury. The knee takes considerable pounding in the course of everyday activities that subject it to repeated impact (such as occurs with walking, running, and jumping). Repetition or “wear and tear” injuries of the knee include OSTEOARTHRITIS and PATELLOFEMORAL SYNDROME.

Symptoms of Knee Injuries and Diagnostic Path

PAIN and swelling are symptoms common to many kinds of knee injuries. Damage to ligaments and menisci often result in an unstable knee that feels “loose” or may not bear the person’s weight. With a moderate to severe injury the person hears and feels a substantial “pop” from the knee, which is the LIGAMENT tearing. Depending on which ligament the injury damages, the knee may feel it wants to bend too far back, extend too far forward, or slip to one side or the other. A significant blow to the side of the knee can cause multiple injuries within the knee, rendering the knee useless. Hyperextension and dislocated patella present characteristic appearances that make the diagnosis obvious. A fractured patella can cause excruciating pain and complete inability to use the knee or leg.

The diagnostic path begins with a detailed accounting of the nature of the pain and description of any precipitating trauma. The doctor will thoroughly examine both knees. Diagnostic procedures may include X-RAY, especially if the doctor suspects a FRACTURE, though COMPUTED TOMOGRAPHY (CT) SCAN or MAGNETIC RESONANCE IMAGING (MRI) typically yield more information about the nature and extent of soft tissue injuries such as are most common in the knee. Diagnostic ARTHROSCOPY, a MINIMALLY INVASIVE SURGERY, may be necessary to fully assess the damage and has the advantage of allowing the surgeon to immediately repair the injury.

InjuryCommon CausesKey Symptoms
anterior cruciate LIGAMENT (ACL) sprain sudden twisting of the knee or blow to the front of the knee pop or snap felt and heard
mild PAIN
“loose” feeling to knee
inability to bear weight on the leg
hyperextension direct blow to the front of the knee pain with hyperextension
soreness after knee returns to normal extension
lateral collateral ligament (LCL) sprain impact to the inside of the knee pain
pop or snap felt and heard
knee buckles to the outside
medial collateral ligament (MCL) sprain impact to the outside of the knee pain
pop or snap felt and heard
knee buckles to the inside
meniscus tear sudden rotation of the upper body with the foot planted pain
clicking or locking within the knee
instability of the knee
patella DISLOCATION impact to the side of the patella
fall that jars the side of the patella
patella obviously out of position, usually to the side of the knee
inability to bend the knee
patella FRACTURE sharp blow to the patella severe pain and swelling
inability to move the knee or bear weight on the leg
patellar TENDON rupture stumbling in an attempt to avoid a fall
landing after a jump from considerable height
tenderness to touch at point of rupture
difficulty bending or extending the lower leg
displaced patella
PATELLOFEMORAL SYNDROME long-term repetitious movement of the knees such as with running and bicycling
poor conditioning
pain with bending or extending the knee
posterior cruciate ligament (PCL) sprain impact or blow to the front of the knee pop or snap felt and heard
mild pain
“loose” feeling to knee
inability to bear weight on the leg


GradeExtent of Injury or DamageSymptoms
grade 1 or first degree minor stretching of LIGAMENT fibers though knee remains stable mild PAIN with pressure to the knee
mild swelling
grade 2 or second degree moderate tear of the ligament with some instability of the knee moderate pain with pressure to the knee
moderate swelling
grade 3 or third degree complete tear of the ligament and its nerves; unstable knee little if any pain with pressure to the knee
pronounced pop felt and heard at time of injury
inability to bear weight or use the knee

Knee Injuries Treatment Options and Outlook

Ice to the knee and restricting movement are the most effective immediate treatments for traumatic injury. Prompt icing can reduce INFLAMMATION and swelling to minimize the severity of the injury. Suspected patella fracture or severe sprain requires immobilization to prevent further damage. Many knee injuries heal with conservative, nonsurgical treatment approaches. The doctor may recommend a knee wrap or brace, depending on the injury. NONSTEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS) relieve inflammation and pain for both traumatic and overuse injuries. Gentle stretching and exercise such as walking help keep the knee flexible and facilitate HEALING.

Mild to moderate ligament sprains often heal without surgery in four to six weeks. Severe ligament sprains and meniscal tears often require surgery to repair. Orthopedic surgeons can perform nearly all such operations arthroscopically, which allows minimal recovery time. PHYSICAL THERAPY facilitates rehabilitation after surgery and most people able to return to regular activities in about six months. Return to sports may require more time, especially for activities of high vulnerability for knee injury such as football, soccer, downhill skiing, and basketball.

Knee Injuries - Risk Factors and Preventive Measures

Contact sports (such as football) and other sports that involve running, twisting, and jumping (such as soccer, basketball, and tennis) expose the knee to direct blows with great risk for injury. Any sport that uses cleats to improve traction (such as track, soccer, and football) has increased risk for knee injury resulting from excessive torsion (twisting under pressure). Sports and athletic activities account for the majority of knee injuries in people under age 25. By midlife, repetitive trauma (such as results from running) begins to take its toll and overuse injuries become more common. Excessive body weight further stresses the knees.

Strong thigh muscles-the quadriceps in the front and the hamstrings in the back-improve stability of the knee. Weight-lifting or RESISTANCE EXERCISE can strengthen these muscles. YOGA is excellent for improving FLEXIBILITY as well as stability of the knees. Knee supports, braces, and protective pads reduce the risk of knee injury in some sports. Proper technique and adequate physical conditioning are crucial elements of injury prevention for any athletic activity. Other preventive measures include stretching and WARM-UP before and after participating in vigorous exercise or sports events.


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