• Structure
  • ACL Injury
  • MCL Injury
  • Meniscus
  • Patella
  • Arthritis
  • Arthroscopy
  • Rehabilitation

The knee joint is a junction of three bones. The femur and the tibia meet to form a hinge joint. In front of them is the patella (kneecap). The patella sits over the other bones and slides when the leg moves.

The ends of the three bones are covered with articular cartilage. This is a tough elastic material that basically cushions the joint. Also helping to cushion the knee are two C-shaped pads of cartilage called menisci. They lie between the tibia and femur. There is a lateral mensicus and a medial meniscus.



Ligaments help to stabilize the knee. These are stron elastic bands of tissue that connect one bone to another. The four main stabilizing ligaments of the knee are the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL).

There are two basic groups of muscles at the knee. In the front of the knee are the quadricep muscles that work to straighten the leg out. In the back of the knee are the hamstring muscles which help to flex the knee.




The anterior cruciate ligament (ACL) is important for knee stabilization.  This is located deep inside the knee joint.  

The ACL helps control how far the tibia can move in relationship to the femur.Injuries to the ACL are very common and most of the time are sports related.  

The sports requiring the foot to be planted and the body to change directions rapidly, such as basketball, are associated with a higher incidence of injury.  

Usually injury will occur to the ACL with a sudden hyperextension or rotational force.  Depending on the activity or sport the mechanism may differ somewhat.  

Soccer, skiing and football are also three common sports where ACL injuries occur.  Often the injured athlete will feel a “pop” in the knee and have sudden pain.  

The athlete may or may not fall to the ground.  Skiers will usually fall.  However, a soccer player or basketball player in mid-stride stopping suddenly and pivoting can suffer an ACL tear and still often be able to ambulate.  

Besides the pop, the knee often swells after an ACL injury.


It is not uncommon for multiple knee structures to be hurt in an injury.  An ACL, MCL and lateral meniscal injury is a common “triad.” 

Activities requiring rotational motion about the knee, including twisting, cutting and jumping sports, are not recommended after an ACL tear because of the risk of cartilage damage.  

The orthopaedic community has realized over the last several years that long term instability of the knee can lead to early arthritis. 

Some activities, however, can be continued with an ACL lax knee.  These are “in-line” sports such as bicycling, light jogging, roller blading and swimming.

MCL Injury

MCL injury is a stretch, partial tear, or complete tear of the medial collateral ligament (MCL) of the knee. 
(The term "medial" means the ligament is on the inside of the knee.)


Alternative Names:

Knee injury - medial collateral ligament (MCL); MCL injury



On physical examination with a medial collateral ligament test, the tightness of the knee joint is unchanged. This test involves bending the knee to 25 degrees and putting pressure on the outside surface of the knee.

Other tests may include:
  • a knee MRI
  • a knee joint X-ray
  • a knee joint X-ray with stress applied



The medial collateral ligament (MCL) is a ligament extending from the upper-inside surface of the tibia (the shin bone) to the bottom-inside surface of the femur (the thigh bone). The ligament stabilizes the joint on the inside of the knee.

The MCL is usually injured by pressure placed on the knee-joint from the outside, resulting in stress on the inside of the knee joint (valgus stress).

It is often injured at the same time as an anterior cruciate ligament (ACL) injury.



  • knee pain and tenderness along the inside of the joint
  • knee swelling may be present
  • knee instability (giving way) may occur


First Aid:

Initial treatment of an MCL injury includes ice to the area, elevation of the joint (above the level of the heart), non-steroidal anti-inflammatory drugs (NSAIDS), and limited physical activity until the pain and swelling subside.

After an initial period of immobilization (usually with a knee brace), gradual mobilization of the knee with strengthening and stretching should be performed. Physical therapy may be helpful to help regain knee and leg strength.

Surgery for isolated tears of the MCL is not usually performed.


Call immediately for emergency medical assistance if:

Call your health care provider if symptoms of MCL injury occur.

Call your health care provider if you are being treated for MCL injury and you notice increased instability in your knee, if pain or swelling return after they initially subsided, or if your injury does not resolve with time.

Also call if you re-injure your knee.



Use proper techniques when playing sports or exercising. Many cases are not preventable.



Longitudinal Tear

Radial Tear

Bucket Handle Tear

Parrot Beak Tear

The meniscus is the distal cartilage tissue that is found between the weightbearing bones of the knee joint.  It acts as a shock absorber.  It is usually very tough and rubbery.  It does grow weaker with age and meniscal tears can occur with fairly minor injuries in older patients.  In younger populations a tear is usually the result of a fairly forceful injury.  When the meniscus tears a piece of cartilage can move abnormally in the joint causing catching, buckling and swelling.  Swelling usually occurs initially and can sometimes continue occurring with a meniscal tear.


If a tear is very small and symptoms resolve quickly and there is just occasional discomfort but no instability, a patient can be treated with an exercise and range of motion program.  If the symptoms continue then a meniscus can be repaired or partially removed arthroscopically.  A large part of a meniscus has no direct blood supply and therefore spontaneous healing on its own is unusual.

To repair a meniscus sutures can be used or new absorbable tact can be used.  Using the newer absorbable tacks all the work can be done without additional incisions in the knee.  In cases where a meniscus cannot be repaired just the offending torn tissue is removed in order to preserve as much cartilage function as possible.

Arthroscopy is done on an outpatient basis.  Usually three small incisions in the knee are used.  The patient is begun on immediate weightbearing and to move the knee as tolerated.


In certain cases where most of the medial or lateral meniscus has been removed meniscus transplantation is now being performed.  This is where a meniscus is transplanted from a cadaver after being appropriately sized by new measurements and studies. 


The patella is your kneecap.  It is a small bone that sits in front of your knee joint.  It actually is embedded in the quadriceps tendon.  It slides in a groove called the trochlea on the femur as the knee moves.  The patella has a thick cartilage lining but is also subject to high stresses.


This is a Latin term meaning “bad cartilage” or breakdown or softening of cartilage.  It is one of the most common problems of the knee.  Running and jumping can aggravate this condition. 

Symptoms include pain in the front of the knee and a crunching or grinding sound with motion.  Swelling can occur at times.  Symptoms seem to be worse with climbing up or down stairs or a hill.  Also, getting up from prolonged sitting can cause pain. 

The cartilage surface on the underside of the patella becomes soft.  Part of the cartilage can become stringy and flake off at times.  Part of the surface may become roughened.  The synovium in the knee which is a normal substance that helps lubricate the knee joint can sometimes be aggravated in this condition and contribute to the grinding feeling.

Initial treatment for chondromalacia patella emphasize strengthening activities. Often a therapist is used to teach a patient quadriceps exercises to help the patella become rebalanced in a sense.  Anti-inflammatory medication can be used temporarily as well as ice.  Occasionally, a therapist may teach an athlete taping techniques that are helpful.  In cases not responsive to conservative treatment, arthroscopy may be helpful.


The normal patella should track in the groove of the femur in a relatively straight manner.  There are varying degrees of malalignment and tracking.  In some cases the patella may tend to track more to the side of the knee or actually be tilted as it goes back and forth in its groove.  On occasion it may actually come partially out of the groove, which is called subluxation.  Some patients have a positive “J-sign” in which, in full extension, the patella tilts and is pulled strongly to the side of the leg. 

The tracking of the patella can be influenced by different things.  Most of it is influenced by the anatomical shape of the knee.  The following can all contribute to the maltracking of the patella:  shallowness of the femoral groove, the angle of the knees (knock-knees), rotation of the hips, foot positioning on the floor (pronation or flat feet), weakness of the quadriceps, and the shape of the patella.

Treatment for this emphasizes quadriceps strengthening.  The middle muscle of the quadriceps, called the vastus medialis obliquus, or VMO, is the muscle that is focused on to try to balance the patella in its motion.  Occasionally, taping can also help with this.  If conservative measures are not helpful, surgical treatment is reasonable.  Rebalancing the kneecap by opening some tissue on the outside of the knee can be done arthroscopically.  Occasionally tightening the medial structures can also help.  In most patients, this type of surgery would be all that they would need.  In some patients with a significant problem and with patella subluxation or dislocation, a more extensive realignment procedure is sometimes used. 


When the patella is completely out of its groove it is called dislocated.  Features listed above contributing to maltracking kneecaps can also attribute to a kneecap that is easier to dislocate.  A common scenario is standing full weightbearing on a leg with a foot planted and twisting the opposite way from the leg and feeling a sudden tear or pop in the knee with the kneecap dislocating.  Sometimes the kneecap will pop back into place by itself and sometimes a trip to a medical facility is needed.  Once a kneecap has dislocated, typically the medial structures become loose and it is easier to re-dislocate.  The danger of patella dislocation or recurrent dislocation is continued abnormal tracking with cartilage damage under the kneecap or cartilage being chipped off as the patella dislocates over the edge of the femur.


Treatment for this again emphasizes strengthening but surgery is more common for this type of patella problem.  Again, arthroscopic release of the tissues on the outside of the knee will sometimes help prevent further dislocating problems.  On occasion, a more extensive procedure is needed.  Either way, strengthening exercises are critical for treatment.



Three basic types of arthritis may affect the knee joint.

1. Osteoarthritis (OA) is the most common form of knee arthritis. OA is usually a slowly progressive degenerative disease in which the joint cartilage gradually wears away. It most often affects middle-aged and older people.

2. Rheumatoid arthritis (RA) is an inflammatory type of arthritis that can destroy the joint cartilage. RA can occur at any age. RA generally affects both knees.

3. Post-traumatic arthritis can develop after an injury to the knee. This type of arthritis is similar to osteoarthritis and may develop years after a fracture, ligament injury or meniscus tear.

Symptoms of Arthritis:

Generally, the pain associated with arthritis develops gradually, although sudden onset is also possible. The joint may become stiff and swollen, making it difficult to bend or straighten the knee. Pain and swelling are worse in the morning or after a period of inactivity. Pain may also increase after activities such as walking, stair climbing or kneeling. The pain may often cause a feeling of weakness in the knee, resulting in a "locking" or "buckling." Many people report that changes in the weather also affect the degree of pain from arthritis.

Making the Diagnosis:

Your doctor will perform a physical examination that focuses on your walk, the range of motion in the limb, and joint swelling or tenderness. X-rays typically show a loss of joint space in the affected knee. Blood and other special imaging tests such as an MRI may be needed to diagnose RA.


Treatment options:

n its early stages, arthritis of the knee is treated with conservative, nonsurgical measures.

  • Lifestyle modifications can include losing weight, switching from running or jumping exercises to swimming or cycling, and minimizing activities such as climbing stairs that aggravate the condition.
  • Exercises can help increase range of motion and flexibility as well as help strengthen the muscles in the leg.
  • Using supportive devices such as a cane, wearing energy-absorbing shoes or inserts, or wearing a brace or knee sleeve can be helpful.
  • Other measures may include applications of heat or ice, water exercises, liniments or elastic bandages.

Several types of drugs can be used in treating arthritis of the knee. Because every patient is different, and because not all people respond the same to medications, your orthopaedic surgeon will develop a program for your specific condition.

  • Anti-inflammatory medications can include aspirin, acetaminophen or ibuprofen to help reduce swelling in the joint.
  • Glucosamine and chondroitin (kon-dro’-i-tin) sulfate are oral supplements may relieve the pain of osteoarthritis.
  • Corticosteroids are powerful anti-inflammatory agents that can be injected into the joint.
  • Hyaluronate (hi-a-lou’-ron-ate) therapy consists of a series of injections designed to change the character of the joint fluid.
  • Special medical treatments for RA include gold salt injections and other disease-modifying drugs.


Surgical Treatment:

If your arthritis does not respond to these nonoperative treatments, you may need to have surgery.

  • Arthroscopic surgery uses fiber optic technology to enable the surgeon to see inside the joint and clean it of debris or repair torn cartilage.
  • An osteotomy cuts the shinbone (tibia) or the thighbone (femur) to improve the alignment of the knee joint.
  • A total or partial knee arthroplasty replaces the severely damaged knee joint cartilage with metal and plastic.
  • Cartilage grafting is possible for some knees with limited or contained cartilage loss from trauma or arthritis.

Orthopaedic surgeons are continuing to search for new ways to treat arthritis of the knee. Current research is focusing on new drugs as well as on cartilage transplants and other ways to help slow the progress of arthritis.



If you have persistent pain, catching, or swelling in your knee, a procedure known as arthroscopy may help relieve these problems.

Arthroscopy allows an orthopaedic surgeon to diagnose and treat knee disorders by providing a clear view of the inside of the knee with small incisions, utilizing a pencil-sized instrument called an arthroscope. The scope contains optic fibers that transmit an image of your knee through a small camera to a television monitor. The TV image allows the surgeon to thoroughly examine the interior of your knee and determine the source of your problem. During the procedure, the surgeon also can insert surgical instruments through other small incisions in your knee to remove or repair damaged tissues.

Modern or contemporary arthroscopy of the knee was first performed in the late 1960s. With improvements of arthroscopes and higher-resolution cameras, the procedure has become highly effective for both the accurate diagnosis and proper treatment of knee problems. Today, arthroscopy is one of the most common orthopaedic procedures in the United States. More than 1.5 million knee arthroscopies are performed in this country each year.

Whether you have just begun exploring treatment options for your problem knee or have already decided, with your orthopaedic surgeon, to have an arthroscopy, this booklet will help you understand more about this valuable procedure.



While monitoring your VMO muscles, making sure you are still getting the contractions there; extend the leg by pushing the leg into the towel. Pump the ankle three times, not letting the tone in that VMO fluctuate. Then slowly and controllably let your leg back down to the table.

Let it relax completely. Tighten it back up. Again pump three times. And again in a controlled manuver, lower your leg back down to the table.

1. Monitoring your VMO   2. Push leg into towel   3. Lift leg 4 - 6 inches   4. Pump ankle 3 times
5. Pump ankle   6. Pump ankle   7. Lower leg   8. Relax & repeat



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