Articular cartilage is a firm rubbery protein material covering the end of a bone. It acts as a cushion or shock absorber between the bones. When articular cartilage breaks down, this cushion is lost, and the bones will grind together. This causes the development of symptoms such as pain, swelling, bone spur formation and decreased motion. Osteoarthritis commonly affects weight bearing joints such as the knee, but it may affect any joint.
Osteoarthritis of the knee (OA Knee) is one of the five leading causes of disability among elderly men and women. The risk for disability from OA Knee is as great as that from cardiovascular disease. Here are some frequently asked questions about OA Knee. OA Knee usually occurs in knees that have experienced trauma, infection or injury. A smooth, slippery, fibrous connective tissue called articular cartilage acts as a protective cushion between bones. Arthritis develops as the cartilage begins to deteriorate or is lost. As the articular cartilage is lost, the joint space between the bones narrows. This is an early symptom of OA Knee and is easily seen on X-rays. As the disease progresses, the cartilage thins, becoming grooved and fragmented. The surrounding bones react by becoming thicker. They start to grow outward and form spurs. The synovium (a membrane that produces a thick fluid that helps nourish the cartilage and keep it slippery) becomes inflamed and thickened. It may produce extra fluid, often known as "water on the knee," that causes additional swelling.
Over a period of years, the joint slowly changes. In severe cases, when the articular cartilage is gone, the thickened bone ends rub against each other and wear away. This results in a deformity of the joint. Normal activity becomes painful and difficult. Several factors may increase the risk of developing osteoarthritis of the knee.
- Heredity: There is some evidence that genetic mutations may make an individual more likely to develop OA.
- Weight: Weight increases pressure on joints such as the knee.
- Age: The ability of cartilage to heal itself decreases as people age.
- Gender: Women who are older than 50 years of age are more likely to develop OA Knee than men.
- Trauma: Previous injury to the knee, including sports injuries, can lead to OA Knee.
- Repetitive stress injuries: These are usually associated with certain occupations, particularly those that involve kneeling or squatting, walking more than two miles a day, or lifting at least 55 pounds regularly. In addition, occupations such as assembly line worker, computer keyboard operator, performing artist, shipyard or dock worker, miner and carpet or floor layer have shown higher incidence of OA Knee.
- High impact sports: Elite players in soccer, long-distance running and tennis have an increased risk of developing OA Knee.
- Other illnesses: Repeated episodes of gout or septic arthritis, metabolic disorders and some congenital conditions can also increase your risk of developing OA Knee.
- Other risk factors are being investigated, including the impact of vitamins C and D, poor posture or bone alignment, poor aerobic fitness and muscle weakness.
OA Knee can be diagnosed in two ways: patient-reported symptoms such as pain or disability or actual physical signs, such as the changes in the joint seen on X-rays. In most cases, both pathology and patient-reported symptoms are present. An evaluation of OA Knee includes a complete history and physical examination. The examination should cover:
- The involved limb
- The spine
- The blood and nervous system
- The joints on either side of the knee, particularly the hip joint, which can also cause knee pain
Initial treatment is generally directed at pain management. OA Knee pain may have different causes, depending on the individual and the stage of the disease. Thus, treatment is tailored to the individual.
A wide range of treatment options is available. You and your doctor should decide together on the course of treatment that's right for you. In general, treatment options fall into five major groups:
- Health and behavior modifications, such as patient education, physical therapy, exercise, weight loss, and bracing
- Drug therapies, including simple pain relievers such as aspirin or nonsteroidal anti-inflammatory drugs, COX-2 specific inhibitors, opiates and stronger drugs for patients who do not respond to other drugs or treatments, and glucosamine and/or chondroitin sulfate
- Intra-articular treatments, including corticosteroid injections or injections of hyaluronic acid (viscosupplementation)
- Surgery, including arthroscopy, osteotomy, and arthroplasty (joint replacement)
- Experimental/alternative treatments such as acupuncture, magnetic pulse therapy, vitamin regimes and topical pain relievers
Osteonecrosis of the knee
Knee pain has many causes. A relatively common cause of knee pain in older women occurs when a segment of bone loses its blood supply and begins to die. This condition is called osteonecrosis, which literally means "bone death."
In the knee, the knobby portion of the thighbone on the inside of the knee (the medial femoral condyle) is most often affected. However, osteonecrosis of the knee may also occur on the outside of the knee (the lateral femoral condyle) or on the flat top of the lower leg bone (tibial plateau). The exact cause of the disease is not yet known. One theory is that a stress fracture, combined with a specific activity or trauma, results in an altered blood supply to the bone. Another theory supposes that a build-up of fluid within the bone puts pressure on blood vessels and diminishes circulation. More than 3 times as many women as men are affected; most are over 60 years of age.
Osteonecrosis of the knee is also associated with certain conditions and treatments, such as obesity, sickle cell anemia, lupus, kidney transplants, and steroid therapy. Steroid-induced osteonecrosis frequently affects multiple joints and is usually seen in young patients. Regardless of the cause, if the disease is not identified and treated early, it can develop into severe osteoarthritis.
Signs and symptoms
- Sudden pain on the inside of the knee, perhaps triggered by a specific activity or minor injury
- Increased pain at night and with activity
- Swelling over the front and inside of the knee
- Heightened sensitivity to touch in the area
- Limited motion due to pain
Osteonecrosis of the knee develops through four stages, which can be identified by symptoms and X-rays.
Stage I: Symptoms are most intense in the earliest stage. Symptoms may continue for 6 to 8 weeks and then subside. Because X-rays are normal, a positive magnetic resonance is needed to make the diagnosis. Treatment at this point is nonoperative and conservative, focusing on pain relief and protected weight-bearing, and in some cases core decompression (see later).
Stage II: It may take several months for the disease to progress to Stage II. At this point, X-rays will show that the rounded edge of the thighbone is starting to flatten out. An MRI or bone scan can be used to diagnose the disease. A CT scan may also be used to measure the affected area of bone area.
Stage III: By the time the disease reaches stage III (3 to 6 months after onset), it is clearly visible on X-rays and no other diagnostic tests are needed. The articular cartilage covering the bone begins to loosen as the bone itself begins to die. Operative treatments may be considered at this point.
Stage IV: At this point, the bone begins to collapse. The articular cartilage is destroyed, the joint space narrows, and bone spurs may form. Severe osteoarthritis results and joint replacement surgery may be necessary.
In the early stages of the disease, treatment is nonoperative. If the affected area is small, this treatment may be all that is needed. Options include:
- Medications to reduce the pain
- A brace to relieve pressure on the joint surface
- A conditioning program with exercises to increase the strengthen of the muscles in your thighs
- Activity modifications to reduce knee pain
If more than half of the bone surface is affected, you may need surgical treatment. Several different procedures may be used to treat osteonecrosis of the knee. Among the surgical options are:
- Arthroscopic cleansing (debridement) of the joint
- Drilling to reduce pressure on the bone surface (core decompression)
- Procedures to shift weight-bearing away from the affected area
- Replacement of one or both joint surfaces
Clinical: Clinical presentation is summarized in the following table.
Table 1. Clinical Presentation of SPONK and Secondary Osteonecrosis
||Typically >55 y
|Associated risk factors
||Corticosteroids, alcohol, SLE, sickle-cell disease, caisson disease, Gaucher disease, fat emboli, thrombi formation
|Other joint involvement
||Approximately 80% bilateral
||One (usually medial femoral condyle or either tibial plateau)
||Epiphyseal to the subchondral surface
||Diaphyseal, metaphyseal, epiphyseal
||Commonly sudden onset of pain and increased pain with weightbearing, stair climbing, and at night
||Usually long-standing insidious pain; patient may have symptoms and signs of an underlying disorder, such as SLE
||Pain localized to affected area; small synovitis or effusion may occur; ligaments are stable; range of motion may be limited by pain or effusion
||Pain is difficult to localize; ligaments are stable; range of motion is grossly intact but may be limited by pain
One of the most commonly injured parts of the knee, the meniscus is a wedge-like rubbery cushion where the major bones of your leg connect. Meniscal cartilage curves like the letter "C" at the inside and outside of each knee. A strong stabilizing tissue, the meniscus helps the knee joint carry weight, glide and turn in many directions. It also keeps your femur (thighbone) and tibia (shinbone) from grinding against each other.
Football players and others in contact sports may tear the meniscus by twisting the knee, pivoting, cutting or decelerating. In athletes, meniscal tears often happen in combination with other injuries such as a torn ACL (anterior cruciate ligament). Older people can injure the meniscus without any trauma as the cartilage weakens and wears thin over time, setting the stage for a degenerative tear.
Signs and symptoms
You might experience a "popping" sensation when you tear the meniscus. Most people can still walk on the injured knee and many athletes keep playing. When symptoms of inflammation set in, your knee feels painful and tight. For several days you have:
- Stiffness and swelling.
- Tenderness in the joint line.
- Collection of fluid ("water on the knee").
Without treatment, a fragment of the meniscus may loosen and drift into the joint, causing it to slip, pop or lock-your knee gets stuck, often at a 45-degree angle, until you manually move or otherwise manipulate it. If you think you have a meniscal tear, see your doctor right away for diagnosis and individualized treatment.
Tell your doctor exactly what happened and when. He or she may conduct physical testing to evaluate the extent of your meniscal tear. You may need X-rays to rule out osteoarthritis or other possible causes of your knee pain. Sometimes your doctor may use a magnetic resonance imaging scan to get a better look at the soft tissues of your knee joint. Your doctor may also use a miniature telescope (arthroscope) to see into your knee joint, especially if your knee locks.
Menisci tear in a number of different ways:
- Young athletes often get longitudinal or "bucket handle" tears if the femur and tibia trap the meniscus when the knee turns.
- Less commonly, young athletes get a combination of tears called radial or "parrot beak" in which the meniscus splits in two directions due to repetitive stress activities such as running.
- In older people, cartilage degeneration that starts at the inner edge causes a horizontal tear as it works its way back.
Initial treatment of a meniscal tear follows the basic RICE formula: rest, ice, compression and elevation, combined with nonsteroidal anti-inflammatory medications for pain. If your knee is stable and does not lock, this conservative treatment may be all you need. Blood vessels feed the outer edges of the meniscus, giving that part the potential to heal on its own. Small tears on the outer edges often heal themselves with rest.
If your meniscal tear does not heal on its own and your knee becomes painful, stiff or locked, you may need surgical repair. Depending upon the type of tear, whether you also have an injured ACL, your age and other factors, your doctor may use an arthroscope to trim off damaged pieces of cartilage.
A cast or brace immobilizes your knee after surgery. You must complete a course of rehabilitation exercises before gradually resuming your activity.
Osteochondritis dissecans (OCD) is a disorder in which a fragment of cartilage and subchondral bone separates from an articular surface. The etiology is uncertain, although trauma and ischemia have been implicated. The knee is most commonly affected, but the elbow and ankle may also be involved. Patients typically present during their adolescent or early adult years with nonspecific knee pain and swelling that worsens with activity. The diagnosis is confirmed by radiographic findings. Management decisions are based on the patient's age and the stability, location, and size of the lesion.
The reported prevalence of OCD is 30 to 60 cases per 100,000 people. Patients usually present in their teenage years (those who have OCD of the patella usually present in their 20s and 30s), but the disorder may manifest later in life. It has been estimated that 4% of all cases of osteoarthritis of the knee diagnosed in men were the direct result of OCD. However, the lesion is not always symptomatic and is sometimes an incidental radiographic finding. Bilateral disease is present in 30% to 40% of patients. Males are affected three times more often than females.
If spontaneous healing doesn't occur, cartilage eventually separates from the diseased bone and a fragment breaks loose into the knee joint, causing locking of the joint, weakness, and sharp pain. An x ray, MRI, or arthroscopy can determine the condition of the cartilage and be used to diagnose osteochondritis dissecans.
If cartilage fragments have not broken loose, a surgeon may fix them in place with pins or screws that are sunk into the cartilage to stimulate a new blood supply. If fragments are loose, the surgeon may scrape down the cavity to reach fresh bone and add a bone graft and fix the fragments in position. Fragments that cannot be mended are removed, and the cavity is drilled or scraped to stimulate new growth of cartilage. Research is currently being done to assess the use of cartilage cell transplants and other tissues to treat this disorder.
Knee ligament treatment options
Ligaments connect one bone to another within a joint and help to provide stability and flexibility. There are four main ligaments in the knee. Injury to each one has slightly different symptoms and treatment. It is possible to damage more than one ligament in the same incident.
The medial collateral ligament is located on the inside of the knee and is taut when the leg is straightened. It is a strong ligament but can be sprained or completely torn (ruptured) when the straightened leg is twisted at the same time as being knocked sidewards. This can be during a contact sport, as with a football tackle, or without contact, as can happen in a fall while skiing. The injured knee is painful and swollen, especially on the medial (inner) side. By examining the knee and seeing how much the lower leg can be moved outwards, while the upper leg is held still, doctors can usually establish how badly the ligament is sprained. Grade I (a sprain) and grade II (partial tear) injuries of the ligament, are more painful than a complete (grade III) tear. Many grade I or II sprains will heal by themselves. A grade III tear usually requires surgery.
The anterior cruciate ligament (ACL) joins the back of the inside of the thighbone to the outside front of the shinbone. Cruciate means in the form of a cross. The ACL is so called because it crosses the posterior cruciate ligament.
The ACL is about half the strength of the medial collateral ligament and is the most commonly injured ligament in sport. Players of football, and other sports that involve running, jumping and landing, are prone to ACL tears or ruptures.
When the ACL is completely ruptured, it is common to hear a distinct popping sound. You may also feel something snap inside the knee. If the knee appears loose, it is usually a sign of an ACL injury. Other symptoms include:
- pain and tenderness
- almost immediate swelling
- an unstable knee, making it difficult to walk
- the knee locking during movement
A doctor tests for an ACL injury by pulling the lower leg forward while holding the thigh still. Treatment depends on how badly the knee is affected by the loss of the ligament and whether this prevents you from doing sport. If you do not ask a lot of your knee, you may not need to have it repaired. Others may need a reconstruction operation, which usually involves taking a graft of tendon (usually from the kneecap) to replace the lost ligament. Intensive physiotherapy to strengthen the thigh muscles (quadriceps) is necessary as part of a programme of rehabilitation.
The posterior cruciate ligament (PCL) joins the inside of the end of the thighbone to the back (posterior) of the shinbone. With the ACL, it forms a cross-shape. Also like the ACL, it helps to stabilise the front to back knee movements. The PCL is stronger than the ACL and therefore less prone to injury. The symptoms of a sprain may be milder than for an ACL injury, with no popping sound. For a suspected PCL injury, your doctor may ask you to lie on your back then raise your legs so that your thighs point straight up, with your knees bent at right angles. If your lower leg sags toward the floor, the PCL is probably torn. Other symptoms of a PCL injury are similar to those in ACL injuries. Less severe injuries can treated by strengthening the thigh muscles. Surgery is often recommended, especially for younger patients.
The lateral collateral ligament is on the outside of the knee. It is rarely injured on its own but may need to be surgically repaired at the same time as other ligaments. Damage to this ligament causes pain and swelling on the outside edge of the knee. In addition to a complete medical history and physical examination, diagnostic procedures for a knee ligament injury may include the following:
- x-ray - a diagnostic test which uses invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs onto film.
- magnetic resonance imaging (MRI) - a diagnostic procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body; can often determine damage or disease in a surrounding ligament or muscle.
- computed tomography scan (Also called a CT or CAT scan.) - a diagnostic imaging procedure that uses a combination of x-rays and computer technology to produce cross-sectional images (often called slices), both horizontally and vertically, of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than general x-rays.
- arthroscopy - a minimally-invasive diagnostic and treatment procedure used for conditions of a joint. This procedure uses a small, lighted, optic tube (arthroscope) which is inserted into the joint through a small incision in the joint. Images of the inside of the joint are projected onto a screen; used to evaluate any degenerative and/or arthritic changes in the joint; to detect bone diseases and tumors; to determine the cause of bone pain and inflammation.
- radionuclide bone scan - a nuclear imaging technique that uses a very small amount of radioactive material, which is injected into the patient's bloodstream to be detected by a scanner. This test shows blood flow to the bone and cell activity within the bone.
Specific treatment for a knee ligament injury will be determined by your physician based on:
- your age, overall health, and medical history
- extent of the injury
- your tolerance for specific medications, procedures, and therapies
- expectation for the course of the injury
- your opinion or preference
Treatment may include:
- muscle-strengthening exercises
- protective knee brace (for use during exercise)
- ice pack application (to reduce swelling)