Knee pain is an extremely common complaint, and there are many causes. It is important to make an accurate diagnosis of the cause of your symptoms so that appropriate treatment can be directed at the cause. If you have knee pain, some common causes include:

Knee Osteoarthritis

Osteoarthritis is the most common type of knee arthritis. Also called wear-and-tear arthritis or degenerative joint disease, osteoarthritis is characterized by progressive wearing away of the cartilage of the joint. As the protective cartilage is worn away by knee arthritis, bare bone is exposed within the joint. Knee arthritis typically affects patients over 50 years of age. It is more common in patients who are overweight, and weight loss tends to reduce the symptoms associated with knee arthritis.

Meniscal Tear

There are two menisci in your knee; each rests between the thigh bone (femur) and shin bone (tibia). The menisci are made of tough cartilage and conform to the surfaces of the bones upon which they rest. One meniscus is on the inside of your knee; this is the medial meniscus. The other meniscus rests on the outside of your knee, the lateral meniscus. These meniscus functions to distribute your body weight across the knee joint. Without the meniscus present, the weight of your body would be unevenly applied to the bones in your legs (the femur and tibia). This uneven weight distribution would cause excessive forces in specific areas of bone leading to early arthritis of knee joint. Therefore, the function of the meniscus is critical to the health of your knee. The two most common causes of a meniscus tear are due to traumatic injury (often seen in athletes) and degenerative processes (seen in older patients who have more brittle cartilage). The most common mechanism of a traumatic meniscus tear occurs when the knee joint is bent and the knee is then twisted.

Anterior Cruciate Ligament

The anterior cruciate ligament, or ACL, is one of four major knee ligaments. The ACL is critical to knee stability, and people who injure their ACL often complain of symptoms of their knee giving-out from under them. Therefore, many patients who sustain an ACL tear opt to have surgical treatment of this injury. The diagnosis of an ACL tear is made by several methods. Patients who have an ACL tear often have sustained an injury to the knee. The injury is often sports-related. They may have felt a "pop" in their knee, and the knee usually gives-out from under them


Posterior Cruciate Ligament

The posterior cruciate ligament, or PCL, is one of four ligaments important to the stability of the knee joint. The anterior cruciate ligament, or ACL, sits just in front of the PCL. The ACL is much better known, in part because injuries to the ACL are much more commonly diagnosed than injuries to the PCL. Interestingly, it is thought that PCL injuries account for about 20 of knee ligament injuries, however, the PCL is seldom talked about because these injuries are often left undiagnosed.

Patellar Tendinitis

The patellar tendon connects the kneecap (the patella) to the shin bone. This is part of the 'extensor mechanism' of the knee, and together with the quadriceps muscle and the quadriceps tendon, these structures allow your knee to straighten out, and provide strength for this motion. The patellar tendon, like other tendons, is made of tough string-like bands. These bands are surrounded by a vascular tissue lining that provides nutrition to the tendon. Patellar tendonitis usually causes pain directly over the patellar tendon.

Chondromalacia Patella

Chondromalacia patella is a common cause of kneecap pain or anterior knee pain. Often called "Runner's Knee," this condition often affects young, otherwise healthy athletes.

Chondromalacia is due to an irritation of the undersurface of the kneecap. The undersurface of the kneecap, or patella, is covered with a layer of smooth cartilage. This cartilage normally glides effortlessly across the knee during bending of the joint. However, in some individuals, the kneecap tends to rub against one side of the knee joint, and the cartilage surface become irritated, and knee pain is the result. The treatment in physical therapy program should emphasize strengthening and flexibility of the muscles of the hips and thighs. Use of nonsteroidal anti-inflammatory medication is also helpful to minimize the pain associated with chondromalacia.

Prepatellar Bursitis

Prepatellar bursitis, also known as housemaid's knee, is a common cause of swelling and pain on top of the kneecap. The name "housemaid's knee" comes from the association of this condition with individuals whose work necessitates kneeling for extended periods of time. Prepatellar bursitis is common in professions such as carpet layers and gardeners. A bursa is a thin sack filled with the body's own natural lubricating fluid. This slippery sack allows different tissues such as muscle, tendon, and skin slide over bony surfaces without catching. These bursa are normally very thin (like a plastic bag with the air sucked out of it), but they do present a potential space that can become inflamed and irritated. This is what is known as bursitis

Patellar Subluxation

The kneecap slides up and down a groove on the end of the thigh bone as the knee bends. This groove is called the trochlea. The kneecap is designed to fit in the center of this groove, and slide evenly within the groove. In some people, the kneecap is pulled towards the outside of the knee. As this happens, the kneecap does not slide centrally within its groove.