Understanding Knee Pain
A rupture of the anterior cruciate ligament is a very painful injury. This ligament is one of the primary restraints that holds the knee together. It provides stability for the femur on the tibia. This stability is compromised when the ACL is torn, leading to a sensation of buckling and the inability to trust the knee. An ACL rupture occurs during a sudden change in direction or pivot. People often hear a popping noise at the time of the injury. This is usually followed by swelling and an unstable knee.
A meniscal tear is another common injury that can lead to knee pain. The meniscus is a rubbery, C-shaped disc that cushions the knee joint and is a commonly injured structure in the knee. People who play contact sports are at high risk for a meniscus injury. A tear often occurs during sudden twisting or a deep squat. Older people who have degenerative changes in their knee may also injure the meniscus with a relatively minor injury.
Arthritis is one of the most common causes of knee problems, and the most prevalent type is osteoarthritis. It results from the breakdown of joint cartilage and underlying bone, leading to swelling, pain, and often deformity. Other forms of arthritis include rheumatoid arthritis and post-traumatic arthritis, both of which can affect the knee joint.
Knee pain is a common symptom affecting individuals of various age groups and is often a result of either traumatic injury or developing degenerative diseases. It is increasingly prevalent compared to the past decades and affects almost 1/4 of the adult population. Common factors include occupational trauma, excessive weight, genetic diseases, or systemic problems such as arthritis.
Prevalence of Knee Pain in Singapore
The problems of knee pain and OA are even more significant in the Asia-Pacific region compared with developed Western countries. The higher prevalence of knee and hip OA in this region can largely be attributed to obesity and significant post-traumatic injuries from motor vehicle accidents and work-related accidents. In the Global Lower Body OA Overview (GOAL) study, conducted from 1998-1999 across 9 Asia-Pacific countries, 459/16,171 participants over 35 years old reported knee OA, with an overall prevalence of lower body OA and knee OA of 31%.
As the population ages, this problem is set to increase. By the year 2030, an estimated 20% of the developed countries’ populations will be 65 years or older. Musculoskeletal conditions are a leading cause of severe long-term pain and physical disability. People with knee OA comprise 11% of all people requiring assistance with long-term care. This reflects a far higher prevalence than OA and is due to the profound disability that knee OA can cause, making it very difficult to shower, meal prepare, and perform other self-care tasks. In the USA, the prevalence of symptomatic knee OA among adults over age 60 was 12.1% between 2003-5. This reflects the increasing age of the population and the trend towards people living longer with significant medical problems. OA for all joints had a prevalence of 27 million US adults in 2005. By 2030, this is expected to escalate to 60 million. The finding, published by Rashmee Patil in a presentation on the US adult scheduled for the 2008 ACR meeting, indicates a 92.2% increase in just 25 years.
There have been no data surveys specifically looking at the prevalence of knee pain Singapore, but it is noteworthy that OA in the knee reaches a prevalence of 8.5%, as reported in the recent National Health Survey. In a study looking at symptoms in the elderly in a low-income Asian country, 25% of participants reported knee pain. The prevalence of knee pain and knee OA increases with age. In the Framingham study, symptomatic knee OA was reported in 3% of men and 5% of women over 30. It escalates to 10% in men and 13% in women over 60. A similar increase in prevalence with age was reported in an HDM study from Taiwan.
Benefits of Early Intervention
In cases of isolated meniscus tears, surgical repair may, at times, be necessary to prevent rapid onset of osteoarthritis. However, those who can increase muscle strength and joint stability prior to surgery may be able to defer surgery to a later date. Postoperative outcomes are generally more positive for those who have stronger, more stable knees during rehabilitation. Therefore, even for such injuries, a period of early treatment can be beneficial in improving the long-term prognosis.
One method that has been well researched in its ability to reduce the incidence of knee osteoarthritis is gait modification. This was first researched by Dr. S Gray at the University of Lancaster, in a small sample of 20 subjects. Half of the subjects underwent gait modification aimed at reducing the loading forces on the knee during walking, and half underwent no such alterations. At 18 months follow-up, those who had undergone gait modification had a significantly higher knee joint cartilage volume, showing that this intervention can be effective in reducing the long-term effects of loading on the knee joint. This can still be relevant to those with ACL injuries, as altered gait patterns are common as a result of weakness and instability. With professional guidance, gait can be retrained to prevent further damage to knee joints.
Early intervention is important for those suffering from knee pain, primarily to prevent further damage. This is particularly relevant in ACL injuries, as the incidence of further damage to the knee joint, especially meniscal tears, is almost 50% in the two years following the injury. For those who already have some degree of osteoarthritis, intervention can prevent further damage to the articular cartilage, a process which, when widespread, often is a precursor to total knee replacement.
Preventing Further Damage
So, in summary, progression to arthritis is often a preventable complication of knee injuries. However, the success of definitive treatment is at least partly dependent on the severity of joint damage at the time of treatment. Step 2 in damage limitation is prevention of progressive degenerative change in chronic conditions, often osteoarthritis in the older population. This will be discussed further in the quality of life section.
For acute traumatic injury, the gold standard of treatment is arthroscopic keyhole surgery. This is an ideal example of how not all knee pain is curable, but it can always be treated! Keyhole surgery is minimally invasive and, by virtue of being on a joint with no direct access into the body, the knee, it is possible to achieve substantial surgical benefits with only minor progression to more severe disease. A simple meniscal repair may prevent that individual from ever developing significant arthritis in that knee. The same surgery performed in 20 years’ time on an old partial meniscal tear that has developed into severe osteoarthritis has a less optimistic prognosis. The meniscal tissue may have been so damaged and attenuated that there is little left to repair. The more severe the arthritis, the less effective the treatment. Faced with a torn meniscus in an arthritic knee, a total knee replacement may be advised. Meniscal surgery in the presence of arthritis has become a damage limitation exercise with the aim of symptomatic relief and enhancement of quality of life. Although total knee replacement is a highly successful operation, it is a last resort for an individual with significant functional demands on their knee. Ideally, it is best avoided until late-stage disease.
Step one is damage limitation. This may sound defeatist as a treatment aim, but is particularly relevant in the case of acute knee injury, e.g. ACL rupture or meniscal tears. The natural history of these injuries is progressive joint surface damage culminating in osteoarthritis. Joint surface damage is what predisposes to early onset arthritis. Nowadays, all joint surface damage can be diagnosed with an MRI scan. If the findings on MRI are addressed in a timely fashion, before irreversible damage has been done, the long-term outlook is very good.
This statement that knee pain cannot be prevented is a very common misconception. In essence, knee pain can easily be prevented and treated. It is, or at least should be, a fact of life! However, at present, the large bulk of knee pain, whether as a result of traumatic injury or degenerative, is simply accepted as being incurable. With the evidence base available today, this is an outdated approach.
Improving Quality of Life
Exercise therapy, or physical therapy, is proven to be beneficial for persons with knee osteoarthritis. Exercises to strengthen the quadricep and hamstring muscles are notable for reducing pain and increasing function of knee joints. Some types of exercise are aimed at coordination and balance, which can reduce the risk of falls and subsequently injury to the joint. Though exercise therapy is beneficial, there is a point at which too much stress on the knee can be harmful. A study has shown that walking in overweight persons can result in a load on knee joints 3-5 times their body weight. With every step, excessive load is exerted on the knee, which could accelerate the degenerative process of arthritis. In this case, weight loss would complement exercise therapy as it would reduce mechanical loading forces on the knee and slow further progression of knee osteoarthritis.
An unhealthy knee affects the quality of life for an individual as it restricts mobility and limits participation in leisure and recreational activities. Moreover, an individual suffering from knee pain may need to give up a job or be less productive at work, which has its own negative effects for the patient and the economy. Early intervention in the form of exercise therapy and weight loss can have a positive impact on the quality of life. People with knee arthritis who exercise have less pain, make stronger gains in physical function, and have fewer functional limitations. Weight loss can slow down the effects of arthritis as every pound lost results in a 4-pound reduction in load exerted on the knee for each step taken.
Avoiding Surgery
Some knee injuries, if left unmanaged, can lead to progressive damage and increased risk of osteoarthritis. Patients may experience loss of muscle strength and the inability to fully straighten the knee. Pain or mechanical symptoms, such as catching or locking, may become frequent. Knee pain may become more widespread and debilitating, and the use of assistive devices such as a cane or walker may become necessary. These are the people who will benefit from partially or totally restricting movement and/or function of the knee joint. Unloader braces, canes, and walkers are all designed to take pressure off of the affected area of the knee and reduce pain. By decreasing the load on the affected compartment, patients may effectively reduce pain and disability. This may be recommended for people with severe pain from bone-on-bone in one area of the knee. In the most severe cases, when the previously mentioned treatment options are no longer effective, a joint replacement may be the only viable option. However, if the symptoms of mild and moderate knee osteoarthritis are addressed at an earlier stage, the chance of slowing or preventing progression to more severe disease is quite high. This is important because the severe stages of knee OA are where the aforementioned increased functional limitation and medical costs are incurred. As such, strategies aimed at reducing the prevalence of severe disease are beneficial to both patients as well as the healthcare system.
Available Treatment Options
For those who are suffering from chronic knee pain, physical therapy has been proven to be effective in many cases. The chief aim of physical therapy is to strengthen the muscles around the knee as they play a vital role in the functioning and movement of the knee joint. Failure of the muscles to absorb the load transmitted to the knee will lead to increased stress on the joint surfaces and the internal derangement of the joint. A strong quadriceps muscle can effectively reduce the pain of knee osteoarthritis with the reduction of load transmitted to the knee joint. Physical therapy also consists of active therapy to improve the range of motion and to reduce pain. The best results are obtained when supervised by a physical therapist.
While the approach of early intervention for knee pain seems to be convincing, what are the options available for treatment where the initial approach does not work or the pain is at the severe stage? Our knee is a complex joint which consists of bone, cartilage, ligaments, and tendons which are vulnerable to injury and degeneration. The treatment options are tailored according to the cause of knee pain and anatomic distribution.
Physical Therapy
A study by Jenshak et al demonstrated that after 9 weeks of isometric exercise training, EMG activity increased significantly in the VMO and VL and resulted in a significant increase in pain-free leg extension. This demonstrates how targeting the specific muscle groups can have a significant impact on normalizing gait patterns and increasing pain-free function. A variety of resistance training techniques can be employed to increase muscle strength. High-intensity isometric exercise has been shown to increase quadriceps strength without aggravating symptoms in patients with knee osteoarthritis. Patellofemoral pain patients have shown good tolerance to short arc quadriceps isometrics in early rehabilitation. More advanced isotonic and isokinetic exercise can be added with progression based on the patient’s tolerance.
Strength is also an important factor in knee rehabilitation. For patients with acute knee pain, strengthening the surrounding musculature is a high priority because muscle atrophy can occur quickly due to pain inhibition. In particular, the quadriceps femoris muscle often demonstrates quadriceps avoidance gait in patients with knee pain. This is a strategy to offload the patellofemoral and tibiofemoral joint and decrease pain, but it leads to further muscle atrophy and weakness.
Joint mobilizations are another effective way to increase flexibility. The grade of movement at the joint is assessed and then specific joint line oscillations are performed in an effort to restore normal joint arthrokinematics. This has been shown to be more effective in the knee joint compared to other joints. Each specific joint mobilization technique can also be correlated to the patient’s symptoms and functional limitations. By doing this, the patient achieves symptom improvement as well as restoration of normal joint movement. This should all be supplemented with a home exercise program to maintain flexibility gains.
The patient’s flexibility is addressed through passive stretches that are held for a prolonged period of time. This is an important first step, as tight muscles negatively affect normal joint mechanics. By elongating these muscles, abnormal forces on the knee are decreased. According to a study on the effects of hamstring stretching on knee pain, for each 1° increase in knee extension, there was a corresponding 5% reduction in Osgood-Schlatter disease pain. This demonstrates how increasing flexibility of the quadriceps can have significant effects on reducing knee pain.
Physical therapy plays a major role in treating patients with knee problems. As with all treatments, the first step is a thorough assessment of the patient’s condition in order to develop the best approach. Flexibility, strength, and alignment are all important factors in the rehabilitation process.
Medications
Anti-inflammatory medications include oral NSAIDs and glucocorticoids. Anti-inflammatory medications are more effective for rheumatological causes of knee pain. However, NSAIDs are not recommended for people with osteoarthritis aged over 75 due to increased risk of gastrointestinal complications and kidney impairment. Long-term use of NSAIDs in osteoarthritis should be balanced against potential side effects on blood pressure, cardiovascular health, and kidney function. These medications should be taken under the guidance of a knee pain specialist, as knee pain may have many other causes and there are potential serious side effects on several body systems. Glucocorticoid adverse effects are also well-documented and include easy bruising, osteoporosis, cataracts, and raised intraocular pressure. It is estimated that $30.6 million Australian dollars was spent on NSAIDs by the Australian government in 2006.
There are two main types of drugs used for the treatment of knee pain. Analgesic medications relieve pain, but have no effect on inflammation. These are recommended for pain control of osteoarthritis. Simple analgesics such as paracetamol are recommended as first-line treatment. Topical non-steroidal anti-inflammatory drugs (NSAIDs) are also used for local pain relief with minimal systemic side effects. Discuss the use of topical NSAIDs with your doctor before using as there may be possible drug interactions or side effects that have not been mentioned in the consumer information pamphlet.
Injections
Injections have been used to treat a variety of musculoskeletal conditions. The most common medications injected into the knee are corticosteroids and hyaluronic acid. Corticosteroids are strong anti-inflammatory medications. They can be very effective in treating the symptoms of osteoarthritis; up to 80% of patients find that a single corticosteroid injection relieves pain. Corticosteroids can also help reduce inflammation and swelling. Hyaluronic acid is a naturally occurring substance in normal joint fluid and is found in high concentrations in healthy joint fluid. The injections are meant to act as a lubricant and a shock absorber. When osteoarthritis breaks down the joint fluid, the hyaluronic acid becomes diluted. The injections can replace the body’s own hyaluronic acid and for some patients, may provide relief from pain. Although less common, a Platelet Rich Plasma injection is a relatively new treatment technique. The idea is to enhance the body’s natural ability to heal itself. A blood sample is obtained from the patient and put into a centrifuge, which separates the PRP from other components of the blood. The concentrated PRP is then injected into the area of the body that needs to be treated. The theory is that growth factors that platelets secrete will initiate tissue repair. While there is still limited evidence showing the efficacy of PRP, studies have shown it to be more effective than a placebo and some patients have found it to be very beneficial for their condition.
Lifestyle Modifications
Lifestyle modifications are an essential and integral part of any holistic medical therapy and the management of knee pain. They are not only essential for the psychological and physical health of the patient, but they are also essential for the prevention of chronic, disabling arthritis. The function of the knee is largely dependent on the strength and coordination of supporting leg muscles. Regular strengthening exercises target the thigh and leg muscles that work to support and stabilize the knee joint. Strong muscles help absorb shock and stress on the knee. A well-recommended program using light weights and isotonic exercises under the supervision of a physiotherapist is the best way to achieve this. A recent randomized controlled trial has shown a specific tailored program of hip strengthening exercises conducted by a physiotherapist to be effective in the alleviation of pain and improved function of sufferers of patellofemoral knee arthritis. This is attributed to the fact that hip muscle strength is crucial in obtaining good patellofemoral joint function.
Seeking Professional Help
In general, greater knowledge about the potential treatments and outcomes from different types of orthopaedic specialists is needed. Patient decision making and disease progression will be studied in more detail in the upcoming OAI observational studies, and work on the choice of arthroplasty as a treatment for end-stage knee OA has been initiated by investigators affiliated with the OAI. Changes in patient preference and health care economics over time will have a great impact on the future work of orthopaedic surgeons and other physicians who treat knee OA. It will be important for practitioners to understand these changing trends in order to best provide their patient population with evidence-based, patient-centered care for prevention and treatment of knee OA. Future blog topics in this series will address some of these trends in health care consumerism, decisions about insurance coverage, and compare types of surgical and non-surgical treatments for knee OA.
Patients with knee pain may first choose to seek help from their primary health care practitioner, but studies have shown that into the late 1990s, referral to orthopaedic services was uncommon in general, and especially among older adults. The choice of specialist is often a very important step in the patient’s pathway to regaining good knee health. Although there are few studies that examine the preferences and decision processes of patients in referral to orthopaedics, one study found that older adults had little knowledge about how to access orthopaedic services, had few preferences about which type of specialist to see, and perceived a lack of choice in testing and treatment. One key factor influencing the choice of specialist is the type of referral from a primary care physician. In managed care systems, choice can be limited or influenced heavily by requirements for insurance preauthorization. High out-of-pocket costs have been shown to lead patients to delay or forgo necessary medical services, including those with knee pain.
Finding a Knee Pain Specialist
Left on their own, most people with chronic knee pain often resort to painkillers, worn mostly for arthritic pain or the most recent bout of trauma. While this may alleviate the pain to some extent, it does not solve the problem away. This coupled with the fact that most joint pain often comes with a degree of limitation in movement means that the muscles around the knee often become deconditioned, leading to further exacerbation of the knee problem and the vicious cycle of pain/inactivity/pain. In view of this, it would be logical to see a physiotherapist who will begin with a detailed examination of the lower limb to help isolate the cause of the knee pain. This may involve referral to an orthopaedic specialist to consider the possibility of knee joint injection for diagnostic purposes. With the advent of minimally invasive arthroscopic techniques, many conditions causing chronic knee pain can be effectively treated by the appropriately trained orthopaedic surgeon, an example being keyhole surgery for a torn meniscal cartilage. This would then require postoperative physiotherapy to rehabilitate the knee to full function. In our above-described scenarios, physiotherapist and orthopaedic surgeon are examples of knee pain specialists.
Importance of Regular Check-ups
Details about the injuries discovered during these regular check-ups by knee specialists were not provided. Patient problems, etiology and comorbidity of knee OA caused by meniscal or ligament injury/cartilage damage, an area of considerable research evidence and knowledge, were discussed. Studies have shown that there are often long time intervals between the occurrence of a traumatic knee injury and the onset of PFP or patellofemoral OA, especially in patients with meniscal injury. Such patients often have high-level general functional and sporting capabilities and gain great benefit from the early intervention by a knee specialist through surgical and non-surgical means. Preventative approaches and treatment of the acute traumatic knee injury are part of current research themes amongst knee specialists. Often, however, the individual with an acute injury to their knee will wait until there is some later onset of pain or functional impairment before consulting a knee specialist. The nature of these patients’ injuries and their potential for altering the natural history of a knee condition indicates a role for early specialist intervention, and this may be facilitated by increased patient and health professional awareness of the benefits of early specialist referral in such cases. Patients with knee OA who have regular check-ups with their knee specialist will normally do so when they have a flare-up in their symptoms. If they are involved in a combined research study at the same time they report this episode, they may be recruited as a ‘case’ so that individuals with early phase knee OA can be compared with those with severe disease and linked with disease progression and outcome measures. This has implications for study design and also for the potential benefit of post-injury or post-operative preventive treatment of symptomatic pre-end stage knee OA.
