Originally published on Pain Medicine News
By Tory McJunkin, MD, Paul Lynch, MD, Jarron Tilghman, MD, Jonthan Carlson, MD, Adam Wuollet, MD, and Edward Swing, PhD
Dear Dr. Genu Wine,
This is a very common question among both primary care and pain management providers. Knee pain is a very common complaint that can be debilitating when severe. A proper evaluation must begin with a thorough history and physical examination.
If the patient is not a surgical candidate, there are several conservative treatment options—such as physical therapy for retraining of proper mechanics, kinesiology taping to improve proprioception, acupuncture and chiropractic treatment—that may alleviate the patient’s symptoms. Depending on the nature of the pain, a variety of analgesic medications may be prescribed, including anti-inflammatory drugs, membrane-stabilizing agents and in severe cases, opioid analgesics. Unfortunately, these medications may not significantly reduce the pain and their long-term compliance may be limited by untoward side effects. Additionally, there are a number of patients who have intractable chronic pain following more invasive treatment options such as a total knee arthroplasty (TKA). Studies have reported that 20% of patients undergoing TKA have persistent postsurgical pain.1 These patients often present to the pain clinic frustrated by the failure of conservative and possible surgical interventions. Fortunately, depending on the pain generator, there is a wide array of interventional treatment options that can be implemented.
The primary nerve innervation of the knee arises anteriorly from the femoral nerve and posteriorly from the sciatic nerve. These nerves give rise to a number of smaller branches which provide sensation to a variety of specific regions around the knee. The saphenous nerve branches from the femoral nerve and provides sensation over the distal aspect of the medial two-thirds of the thigh. The lateral one-third of the distal thigh is supplied by the superficial femoral cutaneous nerve. The superior medial, inferior medial, and middle genicular nerves arise from the tibial nerve—the medial division of the sciatic nerve. The superior lateral, inferior lateral, and recurrent tibial genicular nerves arise from the common peroneal nerve—the lateral division of the sciatic nerve.2
A thorough history and physical can aid the clinician in developing a focused differential diagnosis and effectively managing the patient with knee pain. Specific location of the pain, cause of the pain, duration of symptoms, alleviating and/or exacerbating factors, associated ipsilateral back and/or hip pain, and the outcome of any previous interventions should all be investigated. The physical exam should always begin with inspection of the knee to assess for signs of gross deformity, edema or cellulitis. Provocative exam maneuvers such as the valgus/varus stress, anterior/posterior drawer, Lachman’s test, McMurray’s test and the patellar grind test may provide a great deal of information whether positive or negative. If bony etiology is suspected, imaging should include an x-ray of the knee. However, if soft tissue pathology is suspected, an ultrasound or a magnetic resonance imaging scan of the knee may be more appropriate. Furthermore, given that it is common for knee pain to be a manifestation of referred back or hip pain, imaging of these regions as well as electrodiagnostic studies may be appropriate. Electrodiagnostic studies also should be completed if there is any concern for neuropathy. Correlating the patient’s symptoms and physical exam findings with abnormal diagnostic test results can help to condense the differential diagnosis and aid in tailoring a treatment plan.3
Current Evidence for Interventional Therapy
There is a growing body of literature that supports the use of a variety of interventional procedures in the management of knee pain. Raynauld et al demonstrated improved pain relief with intraarticular steroid injection versus saline over a two-year period with repeated injections every three months.4 Neustadt et al showed that intraarticular hyaluronic acid injections brought about some symptomatic pain relief compared with placebo.5 A study by Choi et al revealed that radiofrequency ablation of the superior medial, superior lateral and inferior medial genicular nerves produced significant pain relief in patients with knee osteoarthritis. Wakitani et al demonstrated repair of articular cartilage defects following intraarticular injection of human autologous mesenchymal stem cells.6
Ultrasound Versus Fluoroscopically Guided Injections
Incorrect placement of injectate within the knee can lead to increased pain and decreased therapeutic benefit. The literature suggests that there is an increased rate of successful intraarticular placement using image guidance compared with blind injections. (i.e., using surface anatomic landmarks). In light of this, ultrasound and fluoroscopy are both frequently used to perform interventional procedures for knee pain. Each has advantages and disadvantages with respect to a given procedure. Fluoroscopy provides better visualization of the knee joint, which improves the likelihood of successful intraarticular injection. Given the relatively radiopaque appearance of periosteum and hardware from prior TKA, this is ideal for genicular nerve blocks. However, the patient is subjected to radiation exposure with its usage. Ultrasound allows for better visualization of soft tissue structures, which can dramatically improve the success rate of peripheral nerve and bursa injections in this region. The normal characteristic appearance of various anatomic structures in the region of the knee aid the interventionalist in target localization. Given the real-time dynamic nature of this imaging modality, the needle tip and/or injectate can be easily visualized for both intra- and extraarticular injections to confirm accurate location.7,8 For ease of access into the intraarticular joint space, we recommend performing procedures with the patient in the supine position with the knee maximally flexed to approximately 135 degrees. It is important to note that ultrasound is user-dependent, which makes for more variable results.
The following is a list of interventional procedures that are commonly performed in the treatment of chronic knee pain.
- Intraarticular knee injections: steroids, hyaluronic acid, traumeel, platelet-rich plasma (PRP) and mesenchymal stem cells
- Extraarticular knee injections: steroids, traumeel, PRP and mesenchymal stem cells
- Trigger-point injections
- Peripheral nerve blocks: saphenous, superficial femoral cutaneous, genicular nerves
- Radiofrequency ablation: saphenous, superficial femoral cutaneous, genicular nerves
- Lumbar sympathetic plexus block (typically at L2 and/or L3 level)
- Peripheral nerve stimulation: saphenous, superficial femoral cutaneous
- Lumbar spinal cord stimulation: treatment of last resort.
- Raynauld JP, Buckland-Wright C, Ward R, et al. Safety and efficacy of long-term intraarticular steroid injections in osteoarthritis of the knee. Arthritis Rheum. 2003;48:370-377.
- Neustadt D, Caldwell J, Bell M, et al. Clinical effects of intraarticular injection of high molecular weight hyaluronan (Orthovisc) in osteoarthritis of the knee: a randomized, controlled, multicenter trial. J Rheum. 2005;32:1928-1936.
- Choi WJ, Hwang SJ, Song JG, et al. Radiofrequency treatment relieves chronic knee osteoarthritis pain: a double-blind randomized controlled trial. Pain. 2011;152:481-487.
- Wakitani S, Imoto K, Yamamoto T, et al. Human autologous culture expanded bone marrow mesenchymal cell transplantation for repair of cartilage defects in osteoarthritic knees. J Osteo Res Soc Inter. 2002;10:199-206.
- Jacobson JA. Introduction. In: Jacobson JA, ed. Fundamentals of Musculoskeletal Ultrasound. Philadelphia, PA: Saunders; 2007:1-14.
- Jacobson JA. Knee ultrasound. In: Jacobson JA, ed. Fundamentals of Musculoskeletal Ultrasound. Philadelphia, PA: Saunders; 2007:224-263.
- Waldman SD. Pain Management. Philadelphia, PA: Saunders; 2011.
- Hurdle M-FB. Ultrasound-guided knee injections. In: Narouze SN, ed. Atlas of Ultrasound-Guided Procedures in Interventional Pain Management. New York, NY: Springer; 2011:331-335.
- Beswick AD, Wylde V, Gooberman-Hill R, et al. What proportion of patients report long-term pain after total hip or knee replacement for osteoarthritis? A systematic review of prospective studies in unselected patients. BMJ Open. 2012;2(1).
Drs. Lynch and McJunkin own and operate Arizona Pain Specialists, a comprehensive pain management practice that provides minimally invasive, clinically proven treatments, with five locations in the greater Phoenix area. They also provide consulting services to other pain doctors around the country through their partner company, Boost Medical. For more information, visit ArizonaPain.com and BoostMedical.com.