Normal Anatomy of the Knee Joint
How does the Knee joint work?
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The knee is one of the largest joints in the body, formed by the lower end of the femur, upper end of the tibia and the patella or kneecap. Several ligaments and muscles attach to the bones of the knee joint to maintain normal motion of the joint. Special cartilaginous tissues known as menisci are placed between the two articular ends of the joint. These act as a cushion between the articular surfaces and absorb the shock during movement.
Knee pain is a common condition affecting individuals from different age groups. It not only affects movement but also impacts the quality of life of the individual. An injury or disease of the knee joint or any structure surrounding the knee can result in knee pain. A precise diagnosis of the underlying cause is important to develop an appropriate treatment plan.
Some of the common causes for knee pain include:
- Arthritis: a condition associated with inflammation of the joint
- Knee ligament injuries
- Torn meniscus
- Patellar tendonitis: inflammation of the patellar tendon which connects the kneecap to the shin bone
- Chondromalacia patellae: softening of the articular cartilage on the undersurface of the kneecap causing knee pain
- Dislocated kneecap
- Baker’s cyst: a fluid-filled swelling in the back of the knee which usually results from another problem such as a meniscus tear
- Knee bursitis: inflammation of the bursae, small fluid-filled sacs located around the joints, usually between a tendon and the bone.
- Plica syndrome: results from inflammation of the synovial tissue of the knee causing knee pain and swelling
- Osgood-Schlatter disease: caused by irritation of the growth plate at the front of the knee joint and is more common in adolescents
- Osteochondritis dissecans: characterized by detachment of a cartilage fragment and a thin layer of the bone from the end of a bone due to inadequate blood supply; these fragments may either stay in place or slide around the joint causing pain and joint instability
- Gout: characterized by sudden, severe attacks of joint pain, with swelling and redness around the joint, caused by accumulation of uric acid crystals in the joints
Knee conditions should be evaluated by your doctor for a proper diagnosis and treatment. A detailed medical history and physical examination of the knee is crucial for the diagnosis. Your doctor may also conduct diagnostic imaging studies such as X-rays, MRI scans, CT scans, and ultrasound. Blood tests may be performed to identify any infection, gout or pseudogout. Sometimes arthrocentesis may also be performed, wherein the fluid from the knee joint is removed and sent for laboratory analysis.
Treatment options depend upon the underlying cause responsible for knee pain. Some of the common treatment options for knee pain include rest, ice and heat application, non-steroidal anti-inflammatory medications, stretching, physical therapy, and cortisone injections.
Sometimes a knee arthroscopy may be performed. Knee arthroscopy is a surgical procedure in which the internal structures of the joint are examined to diagnose as well as treat the underlying problem.
If you experience difficulty or inability to walk, deformity around the joint, inability to bend the knee, knee pain persisting beyond a few days and more at night, or pain associated with swelling, warmth, or redness, you should consult your doctor for immediate medical intervention.
Meniscal tears are one of the most frequently reported injuries to the knee joint. The meniscus is a C-shaped fibrocartilaginus structure in the knee incompletely covering the surface of the tibia where it articulates with the femur. It consists of the medial meniscus, on the inner part of the knee, and the lateral meniscus on the outer aspect of the knee.
The menisci act as shock absorbers protecting the articular surface of the tibia as well as assisting in rotation of the knee. As secondary stabilizers, the intact menisci interact with the stabilizing function of the ligaments and are most effective when the surrounding ligaments are intact.
The majority of the meniscus has no blood supply and for that reason, when damaged, the meniscus is unable to undergo the normal healing process and often requires surgical repair.
In addition, a meniscus begins to deteriorate with age, often developing degenerative tears. Typically, when the meniscus is damaged, the torn pieces begin to move in an abnormal fashion inside the joint.
Menisci may tear because of many reasons as mentioned below:
- Twisting motion
- Over flexing the knee joint
- Pivoting such as in sports activities
- Sudden stopping or deceleration
- Degenerative changes that occur over time can weaken and thin the menisci resulting in meniscal tears
Also, the menisci may tear in different ways. Treatment options will depend upon the type of tear, location of the tear, and the extent of the tear.
Following a twisting type of injury the medial or lateral meniscus can tear. This results either from a sporting injury or may occur from a simple twisting injury when getting out of a chair or standing from a squatting position. Our cartilage becomes brittle as we get older and therefore can tear easier.
The symptoms of a meniscal tear include:
- Pain over the inner or outer side of the knee where the tear occurred
- A “popping” may be felt at the time of injury
- Knee swelling, stiffness, and tightness
- Reduced range of motion
Locking can occur if the torn cartilage gets caught between the femur and tibia preventing straightening of the knee.
Evaluating the source of knee pain is critical in determining your treatment options for relief of the pain. Knee pain should be evaluated by an orthopaedic specialist for proper diagnosis and treatment.
Your physician will perform the following:
- Medical History
- Physical Examination
- Diagnostic tests such as X-rays and MRI scans
Anterior Cruciate Ligament (ACL) Tears
The anterior cruciate ligament, or ACL, is one of the major ligaments of the knee that is located in the middle of the knee and runs from the femur (thighbone) to the tibia (shinbone). It prevents the tibia from sliding out in front of the femur. Together with posterior cruciate ligament (PCL) it provides rotational stability to the knee.
An ACL injury is a sports related injury that occur when the knee is forcefully twisted or hyperextended. An ACL tear usually occurs with an abrupt directional change with the foot fixed on the ground or when the deceleration force crosses the knee. Changing direction rapidly, stopping suddenly, slowing down while running, landing from a jump incorrectly, and direct contact or collision, such as a football tackle can also cause injury to the ACL.
When you injure your ACL, you might hear a “popping” sound and you may feel as though the knee has given out. Within the first two hours after injury, your knee will swell and you may have a buckling sensation in the knee during twisting movements.
Diagnosis of an ACL tear is made by knowing your symptoms, medical history, performing a physical examination of the knee, and performing other diagnostic tests such as X-rays, MRI scans, stress tests of the ligament, and arthroscopy.
Treatment options include both nonsurgical and surgical methods. If the overall stability of the knee is intact, your doctor may recommend nonsurgical methods. Nonsurgical treatment consists of rest, ice, compression, and elevation (RICE protocol); all assist in controlling pain and swelling. Physical therapy may be recommended to improve knee motion and strength. A knee brace may be needed to help immobilize your knee.
Young athletes involved in pivoting sports will most likely require surgery to safely return to sports. The usual surgery for an ACL tear is an ACL reconstruction which tightens your knee and restores its stability. Surgery to reconstruct an ACL is done with an arthroscope using small incisions. Your doctor will replace the torn ligament with a tissue graft that can be obtained from your knee (patellar tendon) or hamstring muscle. Following ACL reconstruction, a rehabilitation program is started to help you resume a wider range of activities.
Knee sprain is a common injury that occurs from overstretching of the ligaments that support the knee joint. A knee sprain occurs when the knee ligaments are twisted or turned beyond its normal range causing the ligaments to tear.
Some of the common causes of a knee sprain include forceful twisting of the knee, sudden stop while running, direct blow to the knee, and fall that results in landing on your knees. The factors that increase the risk of knee sprain include participation in sports activities such as skiing, poor coordination, poor balance, and inadequate flexibility and strength in muscles and ligaments.
The most common symptoms include pain, swelling, bruising, warmth and redness of the skin, and restricted movements. Pain will occur soon after injury and may increase upon moving the knee.
Your doctor will evaluate your child’s condition by physical examination and medical history. Diagnostic tests such as X-ray and MRI scan may be required to confirm the condition and provide treatment.
Immediately following a knee injury and before being evaluated by a doctor, you should initiate the R.I.C.E. method of treatment
- Rest: You must ensure that your child takes rest, as more damage could result from putting pressure on the injured area.
- Ice: Ice packs should be applied over the injury to decrease swelling and pain. Ice should never be placed on the skin directly instead it should be applied over a towel to the affected area for 15-20 minutes four times a day for several days.
- Compression: Wrap the knee with an elastic bandage or compress it with the help of a stocking to minimize the swelling and support the knee.
- Elevation: Elevate your child’s knee above heart level which will help to decrease swelling and pain.
After the RICE treatment, your doctor may suggest your child to wear sling, cast, or a brace which immobilizes the knee joint to prevent it from further movement until healing happens. Medicines are prescribed such as nonsteroidal anti-inflammatory drugs to decrease pain and swelling. Physical therapy includes range of motion exercises such as strengthening and stretching exercises which helps to regain normal functioning of the knee.
There are few preventive measures to reduce your child’s risk of knee sprain.
- Ensure that your child does warm-up exercises or stretches before starting any physical activity or sports.
- Ensure that your child learns proper techniques for sports and exercises which help to decrease stress on muscles, ligament, and tendons.
- Make sure that your child wears proper protective equipment during sports activity which will protect them from injuries.
- Encourage your child to take a break from sports when tired.
Younger children usually respond well to nonsurgical treatments and if the pain persists over a long time, then surgery may be needed to repair the torn ligaments. Knee arthroscopy is a surgical procedure done to repair the torn ligament.
Patellar (kneecap) instability results from one or more dislocations or partial dislocations (subluxations). Patella is the small piece of bone in front of the knee that slides up and down the femoral groove (groove in the femur bone) during bending and stretching movements. The ligaments on the inner and outer sides of patella hold it in the femoral groove and avoid dislocation of patella from the groove.
Any damage to these ligaments may cause the patella to slip out of the groove either partially (subluxation) or completely (dislocation). This misalignment can damage the underlying soft structures such as muscles and ligaments that hold the kneecap in place. Once damaged, these soft structures are unable to keep the patella (kneecap) in position. Repeated subluxation or dislocation makes the knee unstable and the condition is called as knee instability.
Patients with knee instability experience different signs and symptoms such as:
- Pain, especially when standing up from a sitting position
- Feeling of unsteadiness or tendency of the knee to “give way” or “buckle”
- Recurrent subluxation
- Recurrent dislocation
- Severe pain, swelling, and bruising of the knee immediately following subluxation or dislocation
- Visible deformity and loss of function of the knee often occurs after subluxation or dislocation
- Sensation changes such as numbness or even partial paralysis can occur below the dislocation as a result of pressure on nerves and blood vessels
Various factors and conditions may cause patellar instability. Often a combination of factors can cause this abnormal tracking and include the following:
- Anatomical Defect: Flat feet or fallen arches and congenital abnormalities in the shape of the patella bone can cause misalignment of the knee joint.
- Abnormal “Q” Angle: The “Q” angle is a medical term used to describe the angle between the hips and knees. The higher the “Q” angle, such as in patients with Knock Knees, the more the quadriceps pull on the patella causing misalignment.
- Patellofemoral Arthritis: Patellar misalignment causes uneven wear and tear and can eventually lead to arthritic changes to the joint.
- Improper Muscle Balance: Quadriceps, the anterior thigh muscles, function to help hold the kneecap in place during movement. Weak thigh muscles can lead to abnormal tracking of the patella, causing it to subluxate or dislocate.
Your surgeon diagnoses the condition by collecting your medical history and physical findings. He may also order certain tests such as X-rays, MRI or CT scans to confirm the diagnosis.
Treatment for instability depends on the severity of the condition and diagnostic reports. Initially your surgeon may recommend conservative treatments such as physical therapy, use of braces, and orthotics. Pain relieving medications may be prescribed for symptomatic relief. However when these conservative treatments yield unsatisfactory response surgical correction may be recommended.
Considering the type and severity of injury surgeon decides on the surgical correction. A lateral retinacular release may be performed where your surgeon releases, or cuts, the tight ligaments on the lateral side (outside) of the patella enabling the patella to slide more easily in the femoral groove.
Your surgeon may also perform a procedure to realign the quadriceps mechanism by tightening the tendons on the inside or medial side of the knee.
If the misalignment is severe tibial tubercle transfer (TTT) will be performed. This procedure involves the surgeon removing a section of bone where the patellar tendon attaches on the tibia. The bony section is then shifted and properly realigned with the patella and reattached to the tibia with two screws.
Following the surgery rehabilitation program may be recommended for better outcomes and quicker recovery.
Arthroscopy of the Knee Joint
Arthroscopy is a surgical procedure in which an arthroscope is inserted into a joint. Arthroscopy is a term that comes from two Greek words, arthro-, meaning joint, and -skopein, meaning to examine.
The benefits of arthroscopy involve smaller incisions, faster healing, a more rapid recovery, and less scarring. Arthroscopic surgical procedures are often performed on an outpatient basis and the patient is able to return home on the same day.
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Total Knee Replacement (TKR)
A total knee replacement (TKR) or total knee arthroplasty is a surgery that resurfaces an arthritic knee joint with artificial metal or plastic replacement parts called ‘prostheses’.
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Anterior Cruciate Ligament (ACL) Reconstruction
The anterior cruciate ligament is one of the major stabilizing ligaments in the knee. It is a strong rope-like structure located in the center of the knee running from the femur to the tibia. When this ligament tears unfortunately it doesn’t heal and often leads to the feeling of instability in the knee.
ACL reconstruction is a commonly performed surgical procedure and with recent advances in arthroscopic surgery can now be performed with minimal incision and low complication rates.
ACL Reconstruction Hamstring Tendon
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ACL Reconstruction Patellar Tendon
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Unicondylar Knee Replacement
This simply means that only a part of the knee joint is replaced through a smaller incision than would normally be used for a total knee replacement. The knee joint is made up of 3 compartments, the patellofemoral, medial, and lateral compartments between the femur and tibia (i.e. the long bones of the leg). Often only one of these compartments wears out, usually the medial one. If you have symptoms and X-ray findings suggestive of this then you may be suitable for this procedure.
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Revision Knee Replacement
This means that complete or a part of your previous knee replacement needs to be revised. This operation varies from a very minor adjustment to a massive operation replacing significant amount of bone and hence is difficult to describe in full.
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Arthroscopic Debridement – Knee
Osteoarthritis is a most common form of arthritis which affects the articular cartilage (tissue covering the ends of the bones) of the knee and also other joints such as shoulder, hip, ankle, and foot. The articular cartilage cushions the joint so that there is smooth and pain-free movement between the bones in the joint. In this condition the articular cartilage is completely worn off, as a result the ends of the bones rub against each other causing pain and inflammation.
Other symptoms include restricted motion of the knee, stiffness in the muscles, and redness and warmth around the joint.
Your doctor will perform physical examination to look for joint swelling, tenderness, and limited range of motion. X-ray of the affected joint may be taken to see the loss of joint space.
If conservative treatment such as medications and physical therapy does not provide relief then surgery may be considered as the last treatment option.
Arthroscopic debridement or a clean-up is a surgical procedure performed using an arthroscope. In this procedure, the cartilage or the bone that is damaged is removed using surgical instruments and the edges of the articular cartilage that are rough will be smoothened. A wash out or joint lavage is done using a special tool to spray jets of fluid to wash and suck out to remove the remaining debris around the joint. After lavage any remaining loose bodies or fragments are removed. Debridement helps to reduce pain and slows down the progression of arthritis. If you still observe pain and other symptoms because of the underlying cause of arthritis, debridement procedure may be repeated. After undergoing arthroscopic debridement procedure you may return to your sports and other activities much faster in comparison to the other traditional procedures.