You may wish to check out this reference as it might also be relevant in view of one of your other questions:
Knee ® Resurfacing Techniques. Our instrumentation enables surgeons to reliably recreate the patient's anatomy and natural joint line. Posterior referencing ...
www.sulzerortho.com/products/nat_knee/resurfac.htm

Feel for joint line tenderness on medial and lateral joint lines and around the patella. The Joint line is felt best with the knee flexed to 90 degrees. Pain isolated to the joint line especially the posterior joint line suggests a meniscal injury. Also feel the quadriceps and infrapatellar tendons for tenderness. If there is an effusion present or has been one by history, check the posteromedial knee for a mass suggesting a Baker's cyst.
uwcme.org/courses/rheumatology/knee/physicalexam.html

Interestingly, the most reliable sign is palpatory tenderness on the meniscus at the joint line (60-80 percent). According to Kapandji5, rotating the tibia internally will cause the medial portion of the meniscus to move anteriorly. The opposite will occur with tibial external rotation. Kromer1 puts his finger tip in the joint line at the tender area and percusses the finger with his middle finger as in percussing the chest wall in order to elicit tenderness. Sometimes a local swelling may appear on the joint line which may be a meniscal cyst. This usually occurs on the lateral meniscus. Fifty percent of cysts coexist with a meniscal tear.
www.chiroweb.com/archives/10/14/27.html

Basic Anatomy of the Knee. ... lower one third of patella for counterforce on femur. The joint line is palpated and observed. The endpoint should be examined ...
www.nismat.org/orthocor/exam/knee_eval.html

HTH