What Is Arthrodesis?

Arthrodesis is also known as artificial ankylosis or syndesis. It is an operation designed to produce bony ankylosis of a diseased joint often done in joints or bones near the joint affected by infection, tumors, trauma, and paralytic conditions.

It is also used in certain cases of painful osteoarthritis and rheumatoid arthritis as a pain relieving measure.

It is important to understand the difference between ankylosis and arthrodesis. Ankylosis refers to a stiff joint irrespective of the cause for stiffness. Arthrodesis always means that the joint has been fused surgically.

The main disadvantage of arthrodesis is that it sacrifices the movement of joint. Thus the function of the limb is definitely compromised. For example, in the lower limb, energy requirements for ambulation are increased. Read more

Normal Synovial Fluid

Synovial fluid is a thick, stringy fluid found in the cavities of synovial joints. It reduces friction between the articular cartilage and other tissues in joints by  lubricating and cushioning them during movement.

During movement, the synovial fluid held in the cartilage is squeezed out mechanically to maintain a layer of fluid on the cartilage surface. Normal synovium contains synovial lining cells that are 1-3 cells deep. Synovium lines all intracapsular structures except the contact areas of articular cartilage. Read more

Osteoarthritis – Structure of Articular Cartilage

Cartilage is the layer covering a joint. Its main function is to produce smooth articulations among the joint surfaces. Type of cartilage in synovial  joint is hyaline cartilage. Hyaline cartilage is a hard, translucent material rich in Type II collagen and proteoglycan.

To reduce the friction, the cartilage is lubricated by various mechanisms.

Synovial  joints serve as mechanical bearings with  low coefficients of friction. Their three major sources of lubrication are:

Hydrodynamic lubrication

Loading of the articular cartilage causes compression that forces water out of the cartilage. This fluid forms an aqueous layer that separates and protects the opposing surfaces.

Boundary layer lubrication

A small glycoprotein called lubricin, which is produced by synovial lining cells, binds to articular cartilage where it retains a protective layer of water molecules.

Hyaluronic acid

It i s produced by synovial lining cells and lubricates the contact surface between synovium and cartilage. Read more

Hemangioma of Synovial Membrane

Synovial hemangioma is a rare lesion. It is most probably a hamartoma or a congenital vascular malformation rather than a true neoplasm. The disease is most comonly noticed in  adolescents and young adults but th symptoms in most of the case can be traced back to childhood.

Knee is the most common affected site. Ankle, elbow, and shoulder may also be affected. Read more

Pigmented Villonodular Synovitis

In this disease, the synovial membrane proliferates and its surface develops nodules and villi. It also turns into brown colour.

The cause of the condition is unknown. It is thought to be an inflammatory process. It occurs most commonly in young adult.

Two primary forms are described

• Diffuse form that affects the entire synovial lining
• Localized form.

The diffuse form is most common and  involves the large joints, while the localized form typically occurs around the small joints of the hands and feet. Read more

Popliteal Cysts – Diagnosis and Treatment

Diagnosis of politeal cyst is usually evident on clinical examination. Conventional radiography in the anteroposterior, lateral, and oblique projections is done to check fluid density and to rule any other lesion that might give rise to poplliteal swelling.

Ultrasonography helps in assessing th swelling and  can distinguish between fluid and solid mass.Popliteal cysts are best shown by sagittal ultrasound image projection. Ultrsound can also be used o rule vascular tumours by looking at arterial pulsations. Read more

Popliteal Cyst or Baker Cyst – Presentation

Popliteal cyst is a soft-tissue swelling in the posterior aspect of the knee which contains gelatinous fluid.It is also called Baker Cyst named after Dr. William Morrant Baker who first described it. Most common location is distal the popliteal crease under the medial head of the gastrocnemius muscle.

These conditions have also been referred in the past as gastrocnemio-semimembranosus bursae, semimembranosus burse, synovial cysts, posterior herniae of the knee joint.

The condition is unilateral mostly. It is almost twice as common in boys than the girls.

Pathological Findings

The cysts may be either bursal or hernial in origin.  The bursal cysts develops in bursa of the gastrocnemius-semimembranosus bursae. Hernial cysts protrude the capsule to lie outside.

The cysts are medially located mostly but  rarely they are laterally located and occasionally extend into the calf of the leg.

Infiltration by lymphocytes, plasma cells, histiocytes, and even polymorphonuclear cells may be seen in varying degrees. Areas of metaplasia into cartilaginous and osteoid elements may also be there.

Clinical Presentation

Symptoms

• Presence of a swelling in the posterior aspect of the knee is the presenting complaint.
• On occasion there may be stiffness and local pain.

Examination

• A swelling is located distal to the popliteal crease
• Swellingbecomes prominent when the knee is hyperextended and disappears on flexion
• Consistency varies from soft to firm
• Transillumination* test is positive

*The passing of a strong beam of light through a part of the body for medical inspection

Synovial Chondromatosis

Synovial chondromatosis is a condition characterized by the formation of  multiple foci of cartilage in the  synovial membrane of a joint. It also occurs in bursae and tendon sheaths.

When the cartilage is ossified, the condition is called  synovial osteochondromatosis.

This is  a benign condition and is very rare in occurrence. It usually occurs in persons over 40 years of age and occasionally in adolescents. It is twice as common in the males Read more

Treatment of Discoid Meniscus

The menisci in the knee joint are required for

• Compensation of incongruity between the femur and tibia
• In the distribution of joint pressure
• Shock absorber, for stabilization of the knee, in provision of rotation, in spreading of synovial fluid, and in nutrition of articular cartilage.

An intact meniscus transmits 70 to 90 percent of the total load across the knee joint. Therefore, it is desirable to preserve the meniscus whenever possible.

A conservative nonoperative method of management is recommended In the treatment of discoid meniscus  if pain and functional disability are minimal.

SIlent discoid menisci  require no treatment. however, they should be kept under observation.

Conservative measures

• Immobilization of the knee
• Restriction of physical activity
• Progressive exercises for the quadriceps.

Operative Measures

If the knee locking persists their is functional disability or pain partial or complete excision of the discoid meniscus is indicated.

Diagnostic arthroscopy is carried out to know the pathologic changes and the type of discoid meniscus.

Partial resection of the discoid meniscus is preferred when it is of the complete or incomplete type with minimal tearing and slight degeneration

Excision of the entire meniscus is performed when it is of the Wrisberg type  or when it is torn and there is marked degenerations.

Clinical Features and Imaging Findings of Discoid Meniscus

The mere presence of a disc-shaped cartilage does not cause any problem.  Rather, the condition condition is often asymptomatic in infancy and early childhood.

By the sixth or eighth year of life the child may complain of following in the affected knee.

• Snapping
• Click
• Giving way
• Catching

Symptoms may be precipitated by a recent injury, especially in the adolescent.

On examination

• Fullness may be detected in the lateral parapatellar area at the joint line.
• Loud “clunk” is audible during the last 15 to 20 degrees of extension of the flexed knee.

The clunk is produced by the lateromedial movement of the semilunar cartilage.

On extension of the knee joint, the lateral meniscus does not remain in place under the lateral femoral condyle because it is not fixed posteriorly to the tibia, but is dislocated medially onto the intercondylar space by the pull of the short meniscofemoral ligament.

During flexion the ligament relaxes, and the lateral meniscus is replaced in its usual position by the contracting popliteus and coronary ligaments.

• Atrophy of the thigh, joint effusion, and synovial thickening are significantly absent.
• Unless connected with an injury, there is no functional disability.

Forced hyperextension of the knee may elicit pain on the lateral aspect of the joint.

Differential Diagnosis

Other causes of snapping of knee can be

• Meniscall cyst
• Congenital subluxation of the tibiofemoral joint
• Abnormal movement of the popliteus tendon
• Snapping of the tendons about the knee
• Subluxation or dislocation of the proximal tibiofibular joint or of the patellofemoral joint.

Radiographic Imaging

Xrays

Increase in lateral joint space may be found on plain xray  if discoid meniscus is thick. Flattening of the lateral femoral condyleand cupping of the lateral aspect of the tibial plateau are other features

Magnetic resonance imaging

It will clearly depict the configuration of the menisci and is the ivestigation of choice.

Contrast arthrography

About 10 ml of a water soluble contrast agent  is injected into the infra-patellar synovial space through a lateral approach and anteroposterior, lateral oblique, medial oblique, poseroanterior, and lateral views are taken.

The diagnosis of discoid meniscus is made when the meniscus can be demonstrated extending to the intercondylar notch separating the cartilages of the lateral femoral condyle and lateral tibial plateau.

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