The Knee
Knee problems include overuse injuries, acute injuries, arthritis, metabolic processes (diabetes or lupus), and inflammation such as infection. The most common presentation to the doctor is a knee that hurts, or one that feels insecure doing certain activities. Knee afflictions can be treated with exercise programs, medications, and modification of the workplace, as well as with operations.

Anatomy
The knee is comprised of 3 bones that connect with each other: The distal femur (thigh), proximal tibia (upper leg), and the patella (kneecap). The ends of the 2 long bones are coated with a layer of articular cartilage which provides the slippery surfaces. The upper bone is round. The lower bone is flat. There are 2 coupling structures called the menisci between the bones which allow the round femur to fit, or articulate, with the flat tibia. One is on the inner and one is on the outer side of the knee. Ligaments are the strong straps and cords that join the bones and prevent excessive motion, working with the menisci, they maintain knee stability. The entire unit is encased in a capsule, which acts much as a sack or balloon to contain the lubricating joint fluid.

Common Types of Problems
A. Injury: Knee injuries are by far the most common presentation of a patient to an orthopedic surgeon. Any or all of the structures described in the anatomy section can be injured.

Meniscus or Cartilage Tears: There are two types of cartilage that exist at the connecting joints of the knee. The cartilage that coats the end of the tibia and the femur is called articular cartilage. The spacer between the two bones is referred to as the meniscus or fibrocartilage. It is a common injury in sports mishaps. The cartilage can tear due to long-term wear and tear without evidence of trauma. People typically present with complaints of pain that occurs on either side of the knee. Symptoms can include locking or the sensation of the leg giving out.

Anterior Cruciate Ligament Injuries: Anterior cruciate ligament (ACL) injuries have become more prevalent with greater participation in sports. The anterior cruciate ligament plays an important role in pivoting sports. Injuries usually occur as the result of twisting stress. Patients will typically have some episodes of the leg giving out or collapsing immediately afterwards.

Posterior Cruciate Ligament Injuries: These uncommon injuries are difficult to diagnose and unfortunately commonly missed by the primary care provider. They occur with forced straightening of the knee, or backward force on the upper shin with the leg bent. They are often combined with other ligament injuries, adding to the difficulty in diagnosis.

Medial Collateral Ligament Pains: The medial collateral ligament is frequently injured when the lower part of the leg is forced outward with the knee remaining in one position such as in a skiing or basketball injury. A common complaint is that "someone fell on the outer side of my knee", resulting in a pain on the inner side.

Lateral Collateral Ligament Injuries: These are rare, caused by a blow to the inner side on the knee, resulting in a stress on the outer side of the knee.

Patellar Tendon and Quadriceps Tendon Injuries: Those injuries occur most typically through trauma. The patellar tendon and quadriceps ligaments can rupture. These will invariably require some form of surgical intervention.

Fractures: Fractures in the knee region are usually the result of trauma or pathological weakening of the bone and subsequent collapse, such as would happen with osteoporosis or tumor.

B. Arthritis: Arthritis of the knee comes in various forms. The mildest form of arthritis of the knee is referred to as chondromalacia. Chondromalacia is a Latin word meaning softening of the cartilage. In very simplistic terms it represents some very mild arthritis of the knee.

Chondromalacia: The most common presentation is pain with activities involving kneeling or squatting. Getting up and down stairs can be quite difficult. Even sitting for long periods of time with the knees bent, car rides, theaters, etc. can be difficult.
Osteoarthritis: Osteoarthritis, or degenerative arthritis, is part of the normal aging process. The treatment ranges from an exercise program and medications all the way to surgical intervention. For more details regarding surgery.

C. Overuse Injuries: Overuse injuries are prevalent. Various types of inflammatory changes occur when the joint is overused. Some common afflictions are chondromalacia or anterior knee pain, patellar tendinitis, and muscular strains such as those of the hamstrings or quadriceps. These are treated and managed by the orthopedic physician.