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Puncture of the Knee Joint

- Discussion:
- multiple approaches can be used, but a medial approach is easiest w/ knee in extension as the patella can be rocked up anteriorly to
    aid in entry;
- if pt will allow the knee to be flexed to 45 deg., then do so;
- palpate the inferomedial and inferolateral borders of the patella, and enter the knee thru either portal, going just medial or lateral to patellar 
- w/ knee in extension, palpate the tibial plateau & slightly sublux the patella towards the side you are entering;
- enter the joint just above the tibial plateau going under the patella;
- for aspiration the needle is inserted from the side just above the upper border of the patella and level with its lateral border;
- needle enters the suprapatellar bursa but this is always widely continuous w/ joint cavity & is site for draining joint effussions;
- for injection, joint is entered at lower border of patella on either side of patellar ligament;
- needle passes backwards thru infrapatellar fat pad to enter cavity between femoral condyle and meniscus; the site used for arthroscopy
    is on the lateral side of the patellar ligament;
- w/ lower approaches the cartilage of the joint surface & menisci must not be damaged;
    - aspiration through the suprapatellar bursa avoids this possibility