Knee disorders and injuries

The knee joint joins the thigh with the leg and consists of two articulations: one between the femur and tibia, and one between the femur and patella. It is the largest and most complicated joint in the human body. The knee is a mobile trocho-ginglymus (i.e. a pivotal hinge joint), which permits flexion and extension as well as a slight medial and lateral rotation. Since in humans the knee supports nearly the whole weight of the body, it is the joint most vulnerable both to acute injury and the development of osteoarthritis.

Disorders and injury

Knee pain is caused by trauma, misalignment, and degeneration as well as by conditions like arthritis. The most common knee disorder is generally known as patellofemoral syndrome.The majority of minor cases of knee pain can be treated at home with rest, ice but more serious injuries do require surgical care.

One form of patellofemoral syndrome involves a tissue-related problem that creates pressure and irritation in the knee between the patella and the trochlea (patellar compression syndrome), which causes pain. The second major class of knee disorder involves a tear, slippage, or dislocation that impairs the structural ability of the knee to balance the leg (patellofemoral instability syndrome). Patellofemoral instability syndrome may cause either pain, a sense of poor balance, or both.

Age also contributes to disorders of the knee. Particularly in older people, knee pain frequently arises due to osteoarthritis. In addition, weakening of tissues around the knee may contribute to the problem. Patellofemoral instability may relate to hip abnormalities or to tightness of surrounding ligaments.

Cartilage lesions can be caused by:

• Accidents( fractures)
• Injuries
• The removal of a meniscus
• Anterior cruciate ligament injury
• Posterior cruciate ligament injury
• Considerable strain on the knee.
• Any kind of work during which the knees undergo heavy stress may also be detrimental to cartilage. This is especially the case in professions in which people frequently have to walk, lift or squatting. Other causes of pain may be excessive on, and wear of, the knees, in combination with such things as muscle weakness and overweight.

Common complaints:

• A painful, blocked, locked or swollen knee.
• Sufferers sometimes feel as if their knees are about to give way, or may feel uncertain about their movement.

The pain felt by people with cartilage injury does not come from the cartilage itself, but from the irritated tissue surrounding the cartilage, or from pieces of cartilage that have come loose. If cartilage injury goes untreated, the layer of cartilage will continue to gradually wear away, causing arthrosis and gradual immobility.

Overall fitness and knee injury

Physical fitness is related integrally to the development of knee problems. The same activity such as climbing stairs may cause pain from patellofemoral compression for someone who is physically unfit, but not for someone else (or even for that person at a different time). Obesity is another major contributor to knee pain. For instance, a 30-year-old woman who weighed 120 lb at age 18 years, before her 3 pregnancies, and now weighs 285 lb, had added 660 lb of force across her patellofemoral joint with each step.

Common injuries due to physical activity
 
Model demonstrating parts of an artificial kneeIn sports that place great pressure on the knees, especially with twisting forces, it is common to tear one or more ligaments or cartilages.

Anterior cruciate ligament injury

ACL is the most commonly injured ligament of the knee. The injury is common during sports. Twisting of the knee is a common cause of over-stretching or tearing the ACL. When the ACL is injured one may hear a popping sound and the leg may suddenly give out. Besides swelling and pain, walking may be painful and the knee will feel unstable. Minor tears of the anterior cruciate ligament may heal over time, but a torn ACL requires surgery. After surgery, recovery is prolonged and low impact exercises are recommended to strengthen the joint.

Torn meniscus injury

The menisci act as shock absorbers and separate the two ends of bone in the knee joint. There are two menisci in the knee, the medial (inner) and the lateral (outer). When there is torn cartilage, it means that the meniscus has been injured. Meniscus tears occur during sports often when the knee is twisted. Menisci injury may be innocuous and one may be able to walk after a tear, but soon swelling and pain set in. Sometimes the knee will lock while bending. Pain often occurs when one squats. Small meniscus tears are treated conservatively but most large tears require surgery.

Fractures

Knee fractures are rare but do occur, especially after motor vehicle accidents. There is usually immediate pain; swelling and one may not be able to stand on the leg. The muscles go into spasm and even the slightest movements are painful. X-rays can easily confirm the injury and surgery depends on the degree of displacement and type of fracture.

Ruptured tendon

Tendons usually attach muscle to bone. In the knee the quadriceps and patellar tendon can sometimes tear. The injuries to these tendons occur when there is forceful contraction of the knee. If the tendon is completely torn, bending or extending the leg is impossible. A completely torn tendon requires surgery but a partially torn tendon can be treated with leg immobilization followed by physical therapy.

Overuse

Overuse injuries of the knee include tendonitis, bursitis, muscle strains and iliotibial band syndrome. These injuries often develop slowly over weeks or months. Activities that induce pain usually delay healing. Rest, ice and compression do help in most cases. Once the swelling has diminished, heat packs can increase blood supply and promote healing. Most overuse injuries subside with time but can flare up if the activities are quickly resumed. To prevent overuse injuries, warm up prior to exercise, limit high impact activities and keep your weight under control.

Surgical interventions

Before the advent of arthroscopy and arthroscopic surgery, patients having surgery for a torn ACL required at least nine months of rehabilitation, having initially spent several weeks in a full-length plaster cast. With current techniques, such patients may be walking without crutches in two weeks, and playing some sports in but a few months.

In addition to developing new surgical procedures, ongoing research is looking into underlying problems which may increase the likelihood of an athlete suffering a severe knee injury. These findings may lead to effective preventive measures, especially in female athletes, who have been shown to be especially vulnerable to ACL tears from relatively minor trauma.

Articular cartilage repair treatment:

• Arthroscopic debriment of the knee( arthroscopic lavage).
• Mosaïc-plasty.
• Microfracture( Ice-picking).
• Autologous Chondrocyte Implantation.
• Osteochondral Autograft and Allografts.

Diagnostics

The ideal diagnostic test for assessing knee pain is the standing (weight-bearing) x-ray. Magnetic resonance imaging is often used, but it can be overly sensitive; it sometimes detects tears and signs of inflammation in people who have no pain in their knees. Arthroscopy may be used to examine the knee and to remove debris that causes compression.

Several diagnostic maneuvers help clinicians diagnose an injured ACL. In the anterior drawer test, the examiner applies an anterior force on the proximal tibia with the knee in 90 degrees of flexion. The Lachman test is similar, but performed with the knee in only about twenty degrees of flexion, while the pivot-shift test adds a valgus (outside-in) force to the knee while it is moved from flexion to extension. Any abnormal motion in these maneuvers suggests a tear.

The diagnosis is usually confirmed by MRI, the availability of which has greatly lessened the number of purely diagnostic arthroscopies performed.