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The knee is one of the largest, most complex joints in the body. It is made up of four bones: The femur, the tibia, the fibula, and the patella. The muscles that support the knee are the quadriceps, in the front of the knee, and the hamstrings, in the back. These structures are connected through an intricate compilation of ligaments and cartilage. The anterior cruciate ligament (ACL) prevents the femur from moving backwards onto the tibia, and the posterior cruciate ligament (PCL) prevents the femur from sliding forwards. There are two collateral ligaments, medial and lateral, that also help to provide support. The meniscus (lateral and medial) is tissue that sits between the femur and the tibia, providing ease of movement between the two bones. There is also articular cartilage that sits behind the patella. The knee is surrounded by bursae, fluid filled sacs which help to cusion the knee joint.

Types of Knee Pain

The main movement of the knee is bending (flexion) and straightening (extension). The knee is also capable of twisting, which is what accounts for many traumatic injuries to the ligaments of the knee. Some symptoms of this type of injury include a “popping” sound, immediate inability to bear weight on the affected limb, or a sensation that the knee is going to “give way.” These types of injuries typically warrant surgical referral. Twisting can also cause injury to the tendons (tendonitis) or the meniscus. Both of these types of injuries can cause pain and swelling, as well as difficulty straightening the leg. Another main cause of knee pain is degeneration.

Osteoarthritis of the knee is considered a “wear and tear” condition in which the cartilage in the knee degenerates as we age. When osteoarthritis becomes severe, there is no more (or very little) cartilaginous cushion between the knee bones, which can cause significant pain. Chondromalacia patella is also a type of degeneration, and generally means that there is damage to the cartilage beneath the kneecap.

Treatment

The most important aspect of treating knee pain is establishing a diagnosis, usually by way of knee MRI. There are several injections that may help knee pain. One of the most common injections is a corticosteroid injection directly into the knee joint. This type of injection reduces inflammation and pain. Viscosupplementation (Orthovisc, Synvisc) provides lubrication to the knee joint for persons with degenerative conditions such as osteoarthritis. There are also several nerve blocks that may be beneficial.

The most common type of nerve block for knee pain is called a saphenous nerve block, which can provide relief to persons with many types of knee pain, including people who have undergone total knee replacement. Other very helpful treatment modalities for knee pain include chiropractic therapy, gait analysis, bracing, and TENS unit application. Physical therapy can help to strengthen the muscles surrounding the knee joint, improving its stability. Utilizing ice on the knee can help decrease pain and swelling. Anti-inflammatory medications (ibuprofen, naproxen sodium, Celebrex) are the mainstay of treatment for people with knee pain, however other types of medication may be helpful as well.

Neuropathic medications (gabapentin, Lyrica) are beneficial for persons that have neuropathic pain symptomatology (burning, numbness, ‘pins and needles’), and opioid medications (hydrocodone, oxycodone) are beneficial for people with acute knee injuries. If a person is experiencing an acute-type injury of the knee, an orthopedic surgery referral is typically warranted.

If the patient does not respond to more conservative treatments, neuromodulation through spinal cord stimulation may be considered. Spinal cord stimulation involves small electrodes placed within the epidural space of the spine. The theory behind spinal cord stimulation is that stimulation of the large nerve fibers will inhibit the small nerve fibers, thus blocking the sensation of pain. Peripheral nerve stimulation (PNS) is very similar to spinal cord stimulation, but the electrodes are placed along the peripheral nerves, typically close to the area of pain. Under a local anesthetic and minimal sedation your doctor will first place the trial leads into the peripheral space. The trial stimulator is typically worn for 5-7 days and connected to a stimulating device. If the trial successfully relieves your pain you can decide to undergo a permanent SCS/PNS if desired.

Knee pain can be quite disabling, as we use our knees every day for virtually every activity we participate in. At Arizona Pain Specialists, we know we can help. We provide a comprehensive and multidisciplinary approach to your pain. If you suffer from chronic knee pain, please call us to schedule an appointment today!

References:

  • Kim, Philip (2004). Advanced Pain Management Techniques: An Overview of Neurostimulation. Retrieved February 16, 2010 from: http://www.medscape.com/viewarticle/473431 Tennent, TD, Birch, NC, and MJ Holmes (et al)(1998).
  • Knee Pain and the Infrapatellar Branch of the Saphenous Nerve. Journal of the Royal Society of Medicine 1998;91:573-575.
  • The Center for Orthopaedics & Sports Medicine (2003). Knee Joint- Anatomy and Function. Retrieved February 16, 2010 from: http://www.arthroscopy.com/sp05001.htm The Mayo Clinic (2008).
  • Knee Pain. Retrieved February 16, 2010 from: http://www.mayoclinic.com/health/knee-pain/DS00555