As the largest joint in the body, the knee is essential for competing in almost every sport, but it is also the most common site for injury in young athletes. Overall, knee injuries make up about 55% of all sports injuries.
An injury to the knee can cause an athlete to experience pain in many areas of the knee joint. The knee is formed by the convergence of three bones: the femur (upper leg bone), the tibia (lower leg bone) and the patella (kneecap). Two cartilage discs called menisci allow the bones to glide smoothly against each other, absorb shock and act as a cushion between the femur and the tibia. Fluid-filled sacs called bursa surround the outside of the knee. The knee joint is stabilized by muscles, tendons and four critical ligaments: the anterior cruciate ligament (ACL), the posterior cruciate ligament (PCL), the medial collateral ligament (MCL), and the lateral collateral ligament (LCL).
The two major types of knee injuries that an athlete may face are acute injuries and overuse injuries.
How do athletes get knee injuries?
Acute injuries occur suddenly during an activity. In athletes, the most common acute injuries are ACL and MCL sprains. A sprain is the stretching or tearing of a ligament. An ACL injury can occur when an athlete changes direction quickly, stops suddenly, or lands from a jump. MCL injuries often occur in contact sports when the outside of the knee joint is struck.
Overuse injuries are caused by a repeated action or continuous pressure on the knee. Common overuse injuries include:
- Bursitis — inflammation of the bursa
- Patellar Tendinitis (jumper's knee) — inflammation of the patellar tendon, the tendon that connects the patella to the quadriceps muscle
- Patellofemoral Pain Syndrome (runner's knee) — muscle weakness or minor softening of the cartilage under the kneecap that may cause an abnormality in the movement of the patella over the femur
- Osgood-Schlatter disease — inflammation of the patellar tendon where it attaches to the tibia that occurs in growing adolescents
What types of athletes are more prone to knee injuries?
Knee injuries are common in most sports. Often, when a ligament is torn, other tears and strains accompany it. Athletes who play soccer, field hockey, gymnastics, lacrosse, skiing, snowboarding and volleyball are most susceptible to ACL injuries, while MCL injuries are commonly seen in hockey and wrestling. Other sports such as cycling, rugby, running, swimming and water polo are generally more affected by overuse injuries.
What are the common symptoms of knee injuries?
Depending on the location and severity of the injury, symptoms of a knee injury may vary. Symptoms that often coincide with knee pain include:
- Swelling and stiffness
- Warmth and redness
- Limping or instability
- Inability to fully straighten the knee
- "Locking" of the knee
Symptoms of an ACL injury:
- Loud popping sound and immediate pain when the ligament tears
- Swelling occurs within an hour or two
- Knee feels unstable and it is difficult to walk
Symptoms of an MCL injury:
- Grade 1: Partial tear of the MCL. The symptoms are minimal, but athletes may feel pain when pressure is put on the MCL.
- Grade 2: Incomplete tear of the MCL. Athletes may feel that their knee is unstable when they try to change direction or turn quickly. There is pain when pressure is put on the MCL.
- Grade 3: Complete tear of the MCL. Patients are often unable to fully straighten their knee and there is substantial pain and swelling. The knee feels very unstable and may give out.
Symptoms of Bursitis:
- Swelling in the front of the kneecap
- Warmth and tenderness
- Redness in the overlying area of the knee
- Pain during activity
Symptoms of Patellar Tendinitis:
- Pain and swelling around the patellar tendon
- Pain with certain activities such as kneeling or jumping
Symptoms of Patellofemoral Syndrome:
- Aching and discomfort in the front of the knee
- Discomfort is worse going up or down stairs If symptoms are ignored, the quadriceps may lose strength, causing the knee to give out
Symptoms of Osgood-Schlatter disease:
- Pain and swelling where the tibia attaches to the patellar tendon
- Bony growth protruding in the front of the knee at the top of the tibia
What are the common recommended treatments for knee injuries?
ACL injury: Frequently, ACL tears require surgery to replace the ligament. Physical therapy is necessary to rehabilitate the knee and it is usually at least six to nine months before athletes can return to their normal activity level.
Learn about our new Functional Sports Assessment (FSA) for treating ACL injuries.
MCL injury: Fortunately, MCL tears do not usually require surgery. Treatment usually includes rest, anti-inflammatory pain medications and sometimes a brace is necessary to keep the knee from moving from side to side.
Patellar Tendinitis and Bursitis: Treatment for patellar tendinitis and bursitis normally includes rest, icing, and anti-inflammatory pain medications. However, physicians at Midwest Orthopaedics at Rush often treat bursitis with cortisone injections to the inflamed bursa, which is not recommended for patellar tendinitis.
Osgood-Schlatter disease: Osgood-Schlatter disease subsides when the patient is done growing and may be treated with ice and anti-inflammatory medications.