"....articular nerve branches (genicular nerves) for treating knee joint pain due to chronic OA [Choi et al. 2011]. The genicular complex include branches of the femoral, common peroneal, saphenous, tibial, and obturator nerves feeding into the knee joint."
http://updates.pain-topics.org/2011/06/radiofrequency-relieves-chronic-oa-pain.html
Description: The Baylis Medical Co. Inc., which developed the Pain Management SInergy System, a cooled RFD system, was acquired by Kimberly-Clark Worldwide Inc. in 2009 (Kimberly-Clark Corp., 2009). The cooled RF energy device generates heat by radio waves, and is indicated for creating RFD lesions in nerve tissue. The radio waves are delivered to the targeted nerves via needles inserted through the skin above the spine. Sterile water pumped through the device circulates and cools the RF probe. Imaging scans are used to ensure safe and correct placement of the needles. In addition, stimulation of the nerves may be used to identify the location of the needle tip. Once proper placement is confirmed by electrostimulation or fluoroscopy, local anesthetic is injected to minimize the patient's discomfort, and the tip of the needle then heats the surrounding tissue (Kimberly-Clark Worldwide Inc., 2010). This procedure is repeated several times along the surface of the SI joint. In most cases, the procedure is relatively painless; patients may report a mild ache or pulsating feeling in the area during lesioning (Richeimer and Spinasanta, 2010). Through the use of the internally cooled RF probes, the tissue temperature immediately adjacent to the cooled electrode is maintained at 60?C, while the target tissue is heated to 75?C to 80?C, resulting in a lesion diameter ranging from 8 to 10 mm (millimeters). The main advantages of cooled-tip probes are the larger heating distance (up to 3 cm [centimeters] from the active tip), and greater depth of lesioning compared with conventional RFD, which creates lesions ranging from 3 to 4 mm in diameter. The electrodes are inserted at least 5 mm from the foramen to ensure that the temperature within the foramen does not exceed 45?C. An additional advantage of cooled RFD is that the needles are placed using a perpendicular rather than parallel trajectory, which is technically easier and causes less tissue trauma (Cohen et al., 2009; Gupta, 2010).
Above was some other information I found on cooled radiofrequency probes. I guess like you stated it could fall under 64999. I didn't know if 64640 could be used instead.