The kneecap is embedded as a switching bone in the tendon of the large anterior thigh muscle (quadriceps) and primarily serves the power transmission and power distribution.
The back of the kneecap is covered with hyaline cartilage like the other sliding surfaces of the knee joint and slides under flexion and stretch in a channel-shaped recess of the femur. The glide is usually painless and silent. Popping noises are usually not pathological, grating noises can indicate signs of abrasion. Disorders of the sliding usually have the following causes:
1. Dislocation or slipping out of the patella from its bearings (patellar dislocation or subluxation).<br></br>In case of dislocation of the patella - it usually takes place on the outside – shearing injuries to the articular cartilage on the plain edges occur, every time the kneecap disconnects.
2. Hyaline cartilage of the kneecap due to disalignment (chondromalacia patella). Increased pressure (Hyperpression) to a (mostly external) patella facet leads to increased abrasion of the cartilage material and to a constant state of irritation and inflammation of the mucous membrane of the entire knee joint. Due to abrasion and inflammation, the composition of the joint fluid (synovial fluid) is adversely affected, so that there is a further deterioration of the articular cartilage. A vicious cycle follows, that leads to the degeneration and abrasion of the patellar joint (and also other knee joint parts).
3. Femoropatellararthrose (kneecap joint abrasion).
The treatment goal is to center the patella process in plain bearing, to reduce injury to the articular cartilage in the case of disconnection or to stop the process of cartilage abrasion in case of the misalignment of the kneecap (chondromalacia, Hyperpression, osteoarthritis).
1. Centering and pressure relief of the patella:
Portions of the capsule suspension will arthroscopically be cleaved outside with a high frequency electric knife ("lateral release") or possibly gathered inside. Sometimes you have to shift the patellar ligament inwards with a bone bloc (according to the Elmslie surgery). This is however not a arthroscopic but an open surgery.
2. Smoothing of the articular cartilage or bone surface abrasion (see the cartilage damage and osteoarthritis section).
After the arthroscopic treatment of cartilage defects in the knee cap back surface, a rest with forearm crutches ist not necessary, but you should avoid a heavy load on the flexed knee (for example, climbing stairs) for about four weeks.
For arthroscopic capsular shift a plaster cast (upper and lower leg) for four weeks is required, in case of the open dislocation of the patellar ligament surface for six weeks.
In any case, after surgery or after plaster removal intensive physiotherapy is required.
Ability to work
Office work can be resumed about a week after cartilage smoothing and capsule splitting.
Heavy physical work should begin only after four weeks. In case of knee cap abrasion you should double, in transfers of the patellar ligament surface triple the periods.
Usually light jogging, swimming and cycling can be started after about two months.
Depending on the muscle power, more stressful sports such as skiing, tennis, squash, etc. Can be exercised only after three to four months. In case of abrasion or band transfers the periods are extended accordingly.
In about 95 percent, satisfactory results in terms of pain relief and sports ability in cartilage damage stages I and II can be achieved, and in about 75 percent of stage III cases. In stage IV, you should consider a cartilage transplantation or ACI: The success rate of abrasion cases is about 60 percent.
5 percent of patients have a postoperative bleeding in the joint, which makes a puncture necessary. The subsequent result is however not affected. With the introduction of high-frequency surgery, this complication has decreased considerably.
Other complications are comparable to those of other arthroscopic procedures.