Knee pain afflicts millions of Americans and will afflict millions more as the Baby Boomer generation ages. Whether caused by an acute injury—a strain, sprain or tear—or developed over time as a result of wear and tear on the joint, knee discomfort severe enough to interfere with functioning increases with age, as aging knees are more prone to both injury and degenerative conditions.
The knee is the largest joint in the body, and its complexity makes it vulnerable. Injury can occur to the bones, ligaments, and cartilage of the joint itself or to the ligaments, tendons, and bursae that surround the knee. One of the most common injuries is a tear to the meniscus, the cartilage that acts as a shock absorber for the knee. A meniscus tear can result from a sudden movement, often on the playing field, or it can occur in aging knees without an injury as the meniscus weakens, loses elasticity, and becomes more prone to tearing.
Among degenerative conditions that cause knee pain, the most common is osteoarthritis, in which the knee cartilage wears away, causing pain, stiffness, and loss of function. Nearly one in two people will develop osteoarthritis in at least one knee over the course of their lives. And risk rises with increasing body mass index; among the obese, two out of three people are at risk for developing symptoms of osteoarthritis in the knee.1
Treatments for knee pain are as varied as the many causes of the pain. Lifestyle modification, over-the-counter medication, exercise, physical therapy, surgery—all can be effective at least some of the time for some people. But now, new studies have shown that one of the most frequently prescribed treatments—arthroscopic surgery—may be no better than less invasive therapies in relieving knee pain caused by degenerative meniscal tears, and may even exacerbate the problem.
ARTHROSCOPIC SURGERY UNDER THE MICROSCOPE
Arthroscopic surgery revolutionized joint surgery in the second half of the twentieth century with the knee as the model joint for its development. Arthroscopic surgery on the knee generally includes lavage—removing particulate matter such as cartilage fragments and calcium crystals—and debridement, which smoothes the articular surfaces. Compared to traditional open surgical techniques, the small incisions of arthroscopic procedures result in less postoperative swelling, less pain, fewer complications, and faster recovery.
Advances in technique and a rapidly increasing population affected by aging knees have made arthroscopic knee surgery the most frequently performed orthopedic procedure in the United States. There is definitely a place for arthroscopic surgery in the presence of an acute meniscal tear that causes locking, buckling, and catching of the knee. But recent studies have shown that knee arthroscopy may be vastly overprescribed for degenerative tears of the meniscus that cause pain but no mechanical symptoms.
One of the first studies to question the efficacy of knee arthroscopy in relieving pain was published in 2002 and found that in a randomized trial, those who had the surgical procedure for relief of osteoarthritis had no lasting benefit compared to those who had sham surgery.2 For various reasons, the study had little effect in changing clinical practice.
A second study published in 2008 randomly assigned patients with moderate-to-severe osteoarthritis of the knee to two groups.3 Half underwent medical and physical therapy in addition to arthroscopic treatment; the other half had medical and physical therapy alone. After 2 years, both groups’ scores on a measure of arthritis severity were about the same. Taken in conjunction with the results of the 2002 trial, this study did lead to changes that have virtually eliminated knee arthroscopy as a generally recommended treatment for osteoarthritis.
However, the meniscus muddies the picture. MRIs performed on patients who present in the orthopedist’s office with knee pain often reveal a meniscal tear. As a result, arthroscopy—still considered appropriate and reimbursable for a torn meniscus—is performed and, thus, accounts for more than 650,000 procedures each year, according to the National Center for Health Statistics. Now, the effectiveness of that prescription is being called into question as well.
In June 2015, a team of Danish researchers published results of an analysis of nine different trials following patients who had degenerative meniscal tears, both with and without the presence of osteoarthritis.4 Control treatments included sham surgery, medication, and exercise. While arthroscopy conferred a small advantage in pain relief at 6 months, there was no advantage at any point after that and no advantage in improved physical function at any time. The study also noted that surgery had a small risk of adverse side effects, including deep vein thrombosis, infection, and embolism.
Degenerative meniscal tears on their own often cause no symptoms. This has been confirmed by imaging studies that find a partially torn meniscus in many people who report no stiffness or pain. But a degenerative meniscal tear often can be accompanied by osteoarthritis. We find that if a patient has a torn meniscus and reports pain but no locking or catching in the knee—which might indicate the presence of debris catching in the joint—it is likely that the pain has been caused by osteoarthritis rather than the meniscal tear. In those cases, arthroscopic surgery to repair the meniscus will not only not provide lasting relief, it may in fact exacerbate the osteoarthritis.
LESS INVASIVE ALTERNATIVES TO ARTHROSCOPY
The bottom line of these studies and clinical findings is that in many cases, there is little gain—and some risk—in arthroscopic knee surgery. What, then, is the best way to relieve knee pain? In our practice, we see patients helped by a combination of lifestyle modifications, medication, professionally supervised exercise, and several passive therapeutic modalities. These can reduce pain, improve function, and delay or prevent further degeneration that might necessitate a total knee replacement.
Lifestyle modifications include replacing activities that put added stress on the knees, such as running, downhill skiing, tennis, and high-impact aerobics. Substitutes for these types of activities that are easier on the knees include walking, cycling, and swimming. Weight management is also key in preventing the progression of osteoarthritis. To illustrate this point, consider that 10 pounds of extra body weight adds 30 to 60 pounds of force to the knee with every step.
Over-the-counter medications such as aspirin, ibuprofen, and naproxen can provide temporary pain relief. Injections of corticosteroids, which counteract inflammation, and hyaluronic acid, which lubricates joints and reduces swelling, can be administered by a physician for temporary relief.
The most effective solution for long-term pain relief is a program of active and passive physical therapy that can reduce pain and swelling and improve function. The double-edged sword in treating painful knees is that overactivity can make them worse, but too little activity will weaken them further. The therapist can find the right balance for each patient to keep the joints strong and healthy, with a combination of range-of-motion exercises to maintain joint function and improve flexibility, strengthening exercises for the muscles that surround the knee, and aerobic exercise to help control weight.
MODALITIES FOR MANAGING PAIN
Therapeutic modalities can be helpful in programs designed to assist therapists and their patients/clients in managing knee pain. Passive therapies include the application of both heat and cold, depending on the requirements for each patient. Heat increases circulation, relaxes muscles, and reduces stiffness. Cold, in the form of ice packs, sprays, and ointments, numbs the nerves around the knee, slows circulation, and is most effective for reducing swelling. Topical analgesics can also be useful.
The therapeutic effect of ultrasound isn’t fully understood, and its benefits are widely debated. But treating injured tissue by stimulating it with high-frequency sound waves has been used for more than 50 years and is thought to accelerate healing by heating the tissue and by increasing blood flow. It is not used in the presence of malignant tissue, infection, bone fracture, or pregnancy.
Low-level laser therapy (LLLT) is a newer modality that shows promise by reportedly promoting cellular regeneration at the source of the injury. Laser energy helps to repair damaged cells by accelerating the body’s natural healing mechanisms. This treatment works well with manual techniques designed to decrease inflammation and normalize joint/soft tissue mobility. Among the technologies physical therapy clinics use to provide LLLT are class IV and class 3B lasers, with models designed to deliver both continuous wave or pulsed operation.
Electrical impulses are thought to reduce pain by blocking messages to the brain from the nerves. Transcutaneous electrical nerve stimulation (TENS) delivers very low levels of electrical current to the tissues via electrodes attached to the skin. It has been used for many years to ease pain from many conditions, including osteoarthritis of the knee. While TENS does not address the underlying source of the pain, many people—especially those who have difficulty following an exercise program—find it effective for short-term relief.
Neuromuscular electrical stimulation (NMES) stimulates muscles to contract with the goal of re-educating the muscles that support the knee in addition to relieving pain in and around the joint. NMES is effective in strengthening the quadriceps muscle, which tends to be weakened by the pain of osteoarthritis.
Knee osteoarthritis is a degenerative condition, and a meniscal tear is often also precipitated by wear and tear. Arthroscopic surgery is of dubious value in repairing the damage of either or in halting further deterioration. Among some people, the knee will inevitably progress to the point where relief can only be obtained with a total knee replacement. But for many, weight loss, supervised exercise, and a course of physical therapy can delay or even prevent that eventuality and allow the individual to maintain a healthy, active lifestyle. RM
Robert Fay, PT, MHSc, OCS, STC, CSCS, is clinical director and owner at Armonk Physical Therapy and Sports Training. Fay is a board-certified specialist in orthopedic physical therapy, NASMI certified in sports physical therapy, an NSCA-certified strength and conditioning specialist, ACSM-certified fitness instructor, and certified as an advanced hip clinician with the Hospital for Special Surgery. He is a graduate of Northeastern University’s physical therapy program with a masters degree in health science from the University of St. Augustine for Health Sciences. For more information, contact [email protected].