The knee joint is a hinge-type of a joint. The thigh bone (femur) attaches to the shin bone (tibia) with the oval kneecap in the front. The joint may be thought of has having three compartments; the inner, outer and front compartments. There also normally is a thin, smooth covering of cartilage over the bones in the joint that allows normal, smooth and painless motion. There are two larger cushion-like oval cartilages in the knee, which help to stabilize the knee joint; each is called a meniscus the one on the inside is the medial meniscus, and the one on the outside is the lateral meniscus. In addition to these meniscus cartilages, four strap-like ligaments also support and stabilize the knee joint. The ACL and PCL ligaments stabilize the knee against forward and backward pressures. On each side of the joint (medial and lateral) are the collateral ligaments and provide side-to-side stability. The kneecap protects the front of the joint, and also acts as a pulley for the large thigh muscles (quadriceps) which straighten the leg at the knee joint.
Osteoarthritis is sometimes called ‘wear and tear’ arthritis. It may be caused by previous overuse or abnormal use, or due to an injury in the past which damaged the cartilage. Over months or years the damage to the cartilage worsens, and symptoms start. In the case of knee osteoarthritis, the smooth cartilage covering the bones of the joint becomes damaged, rough, torn or thin. The medial meniscus may wear down, often before the lateral meniscus. Injury or abnormal pressure on the joint compartments over time may lead to osteoarthritis. If the kneecap is not in alignment osteoarthritis in the front of the knee can develop. The muscles around the knee support and protect the joint, and injuries or weakness in these may increase the chance of osteoarthritis developing.
Usually the pain is worse with standing and walking. When the knee is at rest there is less pain, but it usually will feel stiffer after a period of rest or inactivity. When moved again, it is more painful. In advanced knee osteoarthritis there may be grinding or creaking noises when the knee is moved. It may lock or give way if the ligaments are not intact, or if there is a tear in a meniscus. The increasing pain and stiffness of osteoarthritis is usually a gradual process.
Along with a history about knee symptoms, a thorough knee examination often suggests osteoarthritis is the diagnosis when pain is felt as the knee is moved and rotated. The normal knee range of motion may be reduced. X-rays are helpful in showing osteoarthritis. An x-ray often shows narrowing of the space between the bones in the joint.
The treatment of knee osteoarthritis depends upon the severity of the pain. Efforts to rebuild joint cartilage are still in the early research stages. Initial treatment to reduce pain often consists of weight loss (if necessary) and exercises to strengthen the knee muscles and reduce the stiffness in the joint. Water exercise classes may be especially helpful. For more severe pain, medications may be recommended. These may include over the counter medications such as Tylenol (generic = acetaminophen) Aleve (generic = naproxen), Motrin (generic = ibuprofen) or aspirin. Various prescription medications which belong to a group of medications called ‘non-steroidal anti-inflammatory medications (or ‘NSAIDs’ for short) are commonly recommended. Some of the more commonly prescribed of these include medications such as Celebrex, Motrin, Naprosyn, Mobic, Voltaren, Relafen and Lodine. (a complete list is available at the reference below). More recently, a medication of a different class called Cymbalta has been approved to treat the pain from osteoarthritis.
More severe pain may be treated with injections of either cortisone-like medications, or lubricating fluids called viscosupplements (such as Hyalgan, Orthovisc, Supartz, or Synvisc) into the joint. If the arthritis is severe, the knee joint may be partially or entirely replaced with surgery.