Tokushukai Medical Group

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Orthopedic Surgery Disease:Patellofemoral Arthrosis

Aching pain by bone deformation.


Fig. 1 Knee side view (Blue colored is cartilage)
There are two joints on knee, one is tibiofemoral joint (so called knee joint) consists with thighbone and Shinbone, and patellofemoral Joint consists with thighbone and patella. (Fig.1) There is cartilage on bone surface at contact point of patella and thighbone to reduce friction. When knee is bent stretched, patella moves smoothly up-down or left-right by cartilage. Patellofemoral Arthrosis is the status which aching pain is produced due to the inflammation developed at patellofemoral joint, cartilage is worn down, or bone is deformed.

Pain when step up/down stairs.

Symptoms are as follows.

Causes are advancing age and bone dislocation/subluxation.

There are mainly two causes.


Fig. 2 Side view of Patellofemoral Joint
The one is the influence of advancing age or cartilage on bone surface is worn out due to continuous placement of burden on knee. Common among middle-aged female, and in most of this case, cartilage of tibiofemoral joint (knee joint) also worn out. The second one is bone dislocation or subluxation. If they are normal, patella is just slipped in the channel formed on thighbone and glide smoothly along the channel. (Fig.2)


Dislocation of Patella
However, when patella comes off from channel (dislocation), or when it is about to come off (subluxation), cartilage is worn out by friction (Fig.3). When patella dislocation or subluxation is repeated, cartilage is damaged further, so that when it turns for the worse, it influences to bone itself. In this case, cartilage of patellofemoral joint (knee joint) will not commonly be influenced.

Dislocation of patella is developed, when muscle at front of thigh (quadriceps muscle) is strongly contracted at jump landing, when plate of knee receives severe impact externally by the accident, or when surrounding ligament (mainly inside) is loosened. It occurs with several reasons. In case where patella or thighbone shape is abnormal by nature and patella does not fit in the channel of patella, it becomes easy to be dislocated. Young female is said they are easy to develop the disease because joint is easy to lose by the influence of female hormone.

Confirm degree of deformation by X-ray photography.

Characteristics or position of pain on knee and movements of patella is observed by diagnosis. X-ray image photography, position of patella, shape of Patellofemoral joint (shape of channel), degree of deformation is confirmed. Remaining volume of cartilage by the size of joint channel is determined by the size of joint channel, and deformed degree is determined with how much unnecessary bones are formed. There may be a case where damaged cartilage position and its degree is confirmed by MRI.

Ease pain by drug therapy and/or physical therapy. When no effect, surgery is conducted.

Conservative treatment is while maintaining the complete rest of affected area, inflammation is blocked so that the relieve pain with drug therapy or physical therapy. When advanced age is the cause, knee surrounding muscle need to be trained and strengthen muscle or ligament then reducing labile of patella. There is a case where attaching equipment so that it prevents patella dislocate to outside.

When no progress can be found in conservative treatment, there may be a case where surgery is conducted although it is rare case. For the case of dislocation due to the advanced age and cartilage of patella is worn out much in volume, there may be the case for artificial knee joint replacement is conducted. In this case, polyethylene cushion is replaced with worn out cartilage, as alternative method.

In case when patella dislocation is the cause of disease, depend on the shape or degree of symptoms, dislocation is prevented by shifting the position of tibia attachment part of patella to prevent from dislocation. Or, surgery is conducted for first to repair ligament at inside of patella so that preventing dislocation to outside.

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