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.