Knee problems are the second most common acute injury in sports (ankles are the first) and the most common overuse/chronic injury. Knee issues come in three general categories: traumatic, acute overload and chronic overuse. I will discuss each one in detail, including what you can do to help prevent knee injuries.
Traumatic
These result from either a direct blow (tackle, direct fall onto the knee) or a sudden twist of the knee (landing incorrectly after a jump or sudden change in direction). The athlete usually is unable to return to play, and swelling can be immediate. The following is a summary of common injuries:

• Fracture (broken bone): Usually from a direct blow
• Dislocation (usually the patella or knee cap): From either a direct blow or a sudden knee twist
• Ligament Tear: Usually from a sudden knee twist. This includes the anterior cruciate ligament, which stabilizes forward knee motion; and the medial or lateral collateral ligaments, located on the either side of the knee, which provide side-to-side stability
• Meniscus (medial or lateral): Usually from a sudden knee twist. The meniscus acts as a cushion between the femur (thigh bone) and tibia (leg bone)
• Bursitis: Usually from a direct blow. The bursas are small fluid-filled sacs that protect tendons from rubbing against underlying bone

The first treatment involves immobilizing the knee and applying ice. If a fracture or dislocation is possible, the athlete should be taken to a hospital emergency room. Prolonged immobility or surgery is often needed for these conditions.
Acute Overload
This occurs when the tissue—bone, tendon or muscle—is suddenly overused, such as by an increase in training intensity over days or weeks. Or it could be a single intense activity—e.g., a 15-mile run as part of marathon preparation. The tissue is not given adequate time to heal before the next training session, leading to pain and inflammation. Common symptoms are a sudden onset of pain along the bone or soft tissue, but without a clear traumatic event. The pain may or may not prevent continual training, but eventually the athlete is unable to train. The following describes common problems:

• Stress Fracture: The bone is unable to heal, which could lead to a complete fracture. Treatment is to stop the activity, perform physical therapy and gradually work back into training, usually over six to eight weeks
• Tendonitis: The tendon is inflamed. The condition includes patella, hamstring, quadricep tendonitis and iliotibial band syndrome
• Bursitis: Rather than suffering a direct blow, the bursa is gradually overworked and then becomes inflamed. Treatment is the same as tendonitis

Treatment for acute overload includes reduction of activity, anti-inflammatory medication and evaluation by a physician or physical therapist as to why the overload happened. Problems could be excessive training, muscle imbalance or poor-fitting equipment. Prevention measures include increasing your training by 10 percent every week to allow tissue healing.
Chronic Overuse
This is most common source of knee pain. Though the causes are similar to those of acute overload, it develops over a longer period of time, so inflammation plays a minimal role. Biomechanical stressors of the knee include improper foot wear, leg length difference, poor core strength and being overweight. Examples of this type of injury include:

• Patella-Femoral Syndrome: Pain under or around the knee cap
• Patella Tendonosis: Knee cap tendon pain without inflammation
• Hamstring Tendonosis: Tendon pain without inflammation
• Degenerative Joint Disease: Also called osteoarthritis
• Anterior Knee Pain
• Medial or Lateral Knee Pain

Treatment is to correct the biomechanical reason for the excess tissue stress. Similar to acute overload, a biomechanical assessment and muscle balance evaluation are critical to identifying causes.
Other strategies to prevent acute overload and chronic overuse of the knee are to ensure good core stability and adequate ankle motion. When the hips and the ankles work better, the knees work better. Included are several lower extremity exercises to reduce knee injuries.
Photo:  sport-africa.net
Dr. Robert Truax is a board-certified doctor in sports medicine, family medicine and osteopathic manipulative treatment at University Hospitals in Cleveland and an assistant professor at Case Western Reserve University’s School of Medicine. Visit uhhospitals.org/SportsMedVideos to watch sports injury videos.