الفهرس 
Anatomy of patellofemoral jointOnly 14 pages are availabe for public view
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Abstract
The patellofemoral joint is the third compartment of the knee joint lying between the posterior surface of patella and the anterior surface of the distal femur .The patella was classified anatomically into four types .The patella has anterior ,posterior surfaces and a base which is thicker superiorly giving attachment for quadriceps femoris muscle ,which have four major components acting as dynamic stabilizers of the patellofemoral joint ,they include vastus medialis, ,rectus femoris muscle,vastus intermedius muscle,vastus lateralis, the distal part of the vastus lateralis inserts onto the lateral patella obliquely thus providing dynamic stabilization against medial displacement .The femoral trochlea is the articular portion of the anterior surface of the distal femur, which articulates with the patella. It consists of a sulcus with lateral and medial facets. The quadriceps tendon it is tri-Laminar having the aponeurosis of insertion of vastus lateralis lies sandwiched between that of vastus intermedius and rectus femoris . The ligametum patellae continues from the patella to the tuberosity of the tibia
The patella has important function as it increases the moment arm of the quadriceps mechanism, provides a cartilage on cartilage articulation with a relatively low coefficient of friction and centralizes the divergent forces of the four heads of the quadriceps and transmitting these forces to the patellar tendon.
It is important to understand the biomechanics of patellofemoral joint,contact areas, contact pressure and reaction force to reach to the aetiology and diagnosis.The pathology of the arthritis is duo to many Risk factors and there are two main causes of osteoarthritis: Primary patellofemoral arthritis and Secondary causes including patellofemoral arthritis after trauma, secondary to malalignmet, secondary to Q angle abnormality, following anterior cruciate reconstruction and duo to systematic Factors such as sex hormones abnormalities, genetic Susceptibility and racial differences.
The Normal cartilage has two main components, collagens (II, IX, & XI) , proteoglycans (mainly aggrecan)and chondrocytes. Disturbance in these components function cause osteoarthritis.
Patellofemoral Osteoarthritis can be diagnosed clinically by inspection, palpation and special examination and by radiology as PXR ,CT and MRI.
Patellofemoral Osteoarthritis can be treated by non pharmacological mearures as Psychosocial reassurance, weight reduction ,temperature Modalities, exercise, orthotics and Bracing ,modification in activities of daily living and Pharmacological treatment as topical agents and systemic agents as non-narcotic analgesics ,non steroidal anti-inflammatory drugs, narcotic analgesics, nutritional supplements and intra-articular injection of steroids or hyaluronic acid derivatives.
Surgical treatment :
The surgical treatment of patellofemoral arthrosis are divided into two categories; For relieving the stresses on the joint and improve the extensor mechanism asarthroscopic lateral retinacular release, lateral Patellar facetectomy, proximal soft-tissue realignment and distal realignment procedures such as anterior or elevation osteotomy of the tibial tubercle ,anterolatralization and anteromedialization of tibial tubercle .And those Operation that directly address the pathology of the articular cartilage include arthroscopic debridement, lavage and cortical abalation, autologus Cartilage transplantation and at the last patellectomy.
Patellofemoral arthroplasty as a treatment of arthritis in late and extensive stages is indicated in Degenerative or posttraumatic osteoarthritis limited to the patellofemoral joint .
Severe symptoms affecting daily activities, failure of a previous surgical procedure to unload the extensor patellofemoral malalignment .
Arthroplasty is contraindicated in: Patella baja (infera), Patella alta , algodystrophy, regional pain syndrome, axis mal-alignment,fixed flexion deformity and Early chondral disease.
Patellofemoral arthroplasty is a relatively new procedure with a legacy that dates back to 1955. Patellofemoral arthroplasty is an option for the treatment of patellofemoral disease arthrosis from primary osteoarthrosis, dysplasia, or posttraumatic arthritis in patients often younger than age 60 years who have normal patellofemoral alignment.
Sparing of the tibiofemoral compartments, menisci, and cruciate ligaments allows preservation of a more kinematically sound knee joint than is typical with TKA, making it an attractive alternative to TKA or patellectomy in this patient cohort. Conversion to TKA is likely to be the salvage procedure after failed arthroplasty; thus, careful patient selection is important. Patellar maltracking from malalignment may result in early failure, underscoring the need to exclude patients with uncorrectable patellar instability or malalignment. The patient who has had a prior distal realignment procedure may be a candidate for the procedure.
. Contemporary designs are associated with reduced incidence of patellofemoral complications, with progressive tibiofemoral arthritis likely representing the primary failure mechanism of these newer implants. Although patellofemoral arthroplasty may have a great value for selected patients, it is important to recognize that most published series have been short or midterm analysis of the procedure. Long-term data, suggest that loosening of cemented trochlear and polyethylene patellar components is uncommon. Further investigation is necessary to determine how these implants will perform over 10 to 20 years and whether younger patients can anticipate long-term success with this procedure using newer prosthesis designs. Long-term failures from tibiofemoral degeneration will occur in at least 25% of patients.
patellofemoral arthroplasty should be considered an intermediate procedure for some patients with isolated patellofemoral arthritis when TKA is not desirable.
custom patellofemoral arthroplasty appears to be a safe and effective treatment for isolated patellofemoral arthritis of the knee.