Knee Pain Diagnostics: How Singaporean Doctors Identify Underlying Issues
Knee pain is a common presenting symptom in a general practitioner’s clinic. There is a wide differential diagnosis of the causes of knee pain ranging from intrinsic knee pathology to referred pain from the hip, lower back or even intra-abdominal sources. This article provides a broad overview of how knee pain is diagnosed. It is important to note that accurate diagnosis of the cause of knee pain relies not only on the history and clinical examination but may also require investigations and the correlation of clinical signs with other clinical findings. This article provides an overview of how clinical diagnosis is supported by specific physical signs and details the further investigations that may be required. These include tests using local anaesthetic for diagnostic purposes and the most relevant use of arthroscopy to confirm the diagnosis of intra-articular knee disorders. This article is written with an understanding of the common problems encountered in general practice. However, it will also be of value to any knee pain doctor Singapore who is involved in the diagnosis and treatment of knee pain.
Common Diagnostic Techniques Used by Singaporean Doctors
Imaging tests are often employed if the diagnosis is unclear or if the doctor suspects a serious injury such as a fracture or a ligament tear. X-rays are generally performed to rule out fractures and to provide a Rice classification if an osteoarthritis problem is suspected. MRIs are commonly used for their soft tissue resolution and are indicated if a more serious problem is suspected, an example being a suspected cruciate ligament or meniscal tear. MRIs will often provide the most accurate information for a wide range of knee problems but are relatively expensive in comparison to other imaging methods. Hence, in a cost vs. diagnostic accuracy sense, MRIs are usually not the first line of imaging used unless the expected diagnostic gains outweigh the costs involved. An ultrasound can also be effective for soft tissue injuries and is relatively cheaper than an MRI.
Physical examination consists of obtaining a patient history, followed by specific questions regarding the nature of the pain (i.e., location, intensity, etc.). Thereafter, the physician will adopt various techniques to try and localize the pain source. This usually involves palpation of the area (i.e., pressing around the knee cap) to determine if the pain is local or diffuse, and testing the range of movement of the knee to see if certain positions/movements reproduce the pain. Specific tests will be performed to attempt to reproduce symptoms, an example being McMurray’s test for a medial meniscus tear. This involves placing the patient’s knee in full flexion, followed by full extension while the physician feels and listens for a clicking in the knee joint.
Physical Examination
Palpation is the process of feeling with the fingers and thumb to detect anything ascertainable by touch. This is important in helping to detect localized pain, swelling, muscle guarding, abnormal tissue, and the health and function of various structures. Effusion can be detected by bulging in the supra-patella pouch, ballottement of the patella, and loss of wave and thrill. The patella can be moved around in a few tests to help detect any patella-femoral problems. The last and in my opinion the most important is palpation of the joint line. This is where the meniscus is situated, and a painful click or jerk is a fairly accurate sign of a tear.
As part of the physical examination, I will find out whether you have any areas of focal tenderness in and around the knee and whether there is any effusion present. Effusion suggests significant intra-articular pathology. The joint line is the area on either side of the knee where the joint is, and pain can be a result of meniscal pathology or ligamentous injuries. In helping to identify the structure that may be damaged by its location of pain, I will get you to point with one finger to the exact site of pain. This may not seem important but is very helpful in differentiating between ligament, meniscal, and articular pathology. With the information gained from these techniques, I will have a clearer idea of what is the probable diagnosis and the best test to confirm this.
Imaging Tests
c) Magnetic Resonance Imaging (MRI) MRI is considered the best available imaging study for the knee. It provides images of all the different soft tissues in the knee and is especially useful in identifying injuries to the ligaments and menisci. An MRI can be useful when x-rays and ultrasound do not find the cause of the problem. However, MRI has restricted availability and higher cost, usually reimbursable only for more complicated cases.
b) Computed Tomography (CT) Scan A CT scan provides much clearer images of the various parts in the knee, especially for details such as a meniscal tear, articular cartilage damage, or osteochondritis dissecans. However, this may expose the patient to a relatively high dosage of radiation.
a) X-ray Examination X-rays are considered the first imaging choice, as they offer simple and practical information. It’s a common test in assessing knee pain, especially in older patients. In older patients, the cause is often osteoarthritis that shows on an x-ray. An x-ray can also be taken to look for signs of infection or tumors. Information obtained from x-rays includes the joint space between the bones and the anatomy of the bones.
Imaging tests are required when a doctor cannot decide how serious the knee injury is or if the diagnosis is unclear. If a patient has significant pain or swelling, the doctor may also request an imaging test to confirm their diagnosis. There are several types of imaging tests that are commonly used:
Laboratory Tests
Though Singaporean doctors sometimes utilize blood or urine tests, the standard laboratory work ordered for knee problems is a diagnostic arthroscopy. Using a local anesthetic, a small instrument is inserted into the knee joint. This is done in the operating room either in the hospital or at an outpatient surgical center. With this tool, your doctor can look at the knee joint and use it to identify problems or take tissue samples (biopsies) from the joint. An arthroscopy may show inflammatory (acute or chronic) changes, cartilage damage, or arthritis. Special tests, known as diagnostic arthroscopies, are sometimes helpful in evaluating unexplained recurrent fluid in a knee joint. By changing the position of the scope and the type and amount of fluid in the joint at the time of the arthroscopy, the doctor may be able to identify the source of the fluid build-up.
Specialized Diagnostic Procedures for Knee Pain in Singapore
Magnetic resonance imaging (MRI) is a non-invasive procedure that does not involve exposure to radiation. MRI provides essential information for understanding anatomy and pathologic conditions and is the most commonly used test for imaging soft tissue damage. In cases where patient history and routine physical exam fails to determine the cause of knee pain, MRI can be a highly useful tool. Using MRI to visualize internal derangement of the knee requires the presence of a surgically treatable lesion for which patient symptoms and physical examination findings cannot accurately define. Random use of MRI is not necessary and patient selection is essential. High-quality images are produced and there are few contraindications to the use of MRI, although the cost of MRI is often viewed as a barrier. Although MRI is an effective mode of diagnosis, it is important to distinguish between asymptomatic abnormalities and those causing pain and dysfunction.
Arthroscopy is the most commonly used method of knee diagnosis in Singapore. It is an invasive procedure involving the use of a fiberoptic telescope inserted into two small incisions at the front of the knee. The extent to which the procedure can diagnose the cause of knee pain makes it a popular choice. Arthroscopy can be used to visualize any soft tissue or bony joint abnormality. The direct visualization of the abnormal structure allows an accurate diagnosis to be made. Tissue samples can be taken during the procedure and abnormal areas can be treated by a number of methods. This may be an advantage if the source of knee pain is identified to be a treatable problem. It has been suggested that a disadvantage of arthroscopy may be the potential inflammatory effects it can have on the knee, with little better results than non-steroidal anti-inflammatory drugs. Another less positive implication from arthroscopy is that sometimes abnormalities can be over-diagnosed and the significance of an abnormal finding can often be ambiguous.
Arthroscopy
The next step up from a simple MRI would be arthroscopic knee surgery. The arthroscopy can actually be used to both diagnose and treat certain knee conditions. The procedure is carried out by orthopedic surgeons, who are registered medical doctors that have been specially trained to operate on the musculoskeletal system. During the surgery, the doctor will make small incisions in the patient’s knee. Saline is then pumped through the knee to expand the joint, allowing for a clearer viewing which reduces risks to injury or excessive pressure to the joint. A camera connected to a fiber optic light source is then inserted through one of the incisions – this is the arthroscope. This projects an image of the inside of the joint onto a screen, allowing the surgeon to conduct a thorough examination of the knee, particularly focusing on the condition of the cartilage, bones, tendons, and ligaments. Other small incisions may be made in the knee if surgical instruments need to be used to correct any problems. These are usually corrective procedures such as removing torn cartilage or rejoining ligament to bone. Under these situations, the arthroscopy has effectively become an alternative to open surgery with a much quicker recovery time for the patient due to less trauma to the knee. After an arthroscopy, it is often possible for the patient to go home on the same day as the surgery. A local or general anesthetic may be used depending on the extent of the procedure and the preference of the patient. This can be discussed with the surgeon prior to the operation. Although arthroscopy is a safe procedure for most people, it may not be recommended for those with certain medical conditions. The decision to proceed with an arthroscopy should be made between the patient and the doctor, after weighing the benefits and risks.
Magnetic Resonance Imaging (MRI)
An MRI of the knee usually takes about 45 minutes to an hour to perform, and a normal report may take up to a week to be returned. This form of diagnosing knee pain is usually safe, but certain contraindications include patients with pacemakers, cerebral aneurysm clips, certain types of artificial heart valves, electronic inner ear implants, and metal fragments in the eyes. This is due to the MRI using a strong magnetic field. Overall, it is an excellent diagnostic tool with relatively few limitations.
The most common indications for a knee MRI include a meniscal tear, ligamentous injury, assessment of the articular cartilage, and diagnosing an occult fracture. When conducting the MRI, it may be done with or without intravenous contrast and in different degrees of flexion of the knee. This may be decided upon by the clinician and radiologist depending on the history of the patient and suspected pathology.
In the past decade, magnetic resonance imaging (MRI) has become the mainstay for assessing internal derangements of the knee. Because of its increased accuracy of soft tissue injury, it has become vastly more popular than diagnostic arthroscopy. It is non-invasive and has no ionizing radiation, yet provides an excellent and detailed image of the joint. It has become an important tool in assessing knee pain where previous plain films and CT scans have not shown any abnormality.
Ultrasound
With conventional equipment, only static images could be obtained – a motor driven transducer having only just been introduced before it became largely obsolete with the introduction of Doppler. Doppler is used to assess the speed and direction of blood flow with the help of the ‘Doppler equation’, and is relevant in musculoskeletal disorders for the assessment of synovitis. Doppler image quality has been improved in recent years with the use of power Doppler which gives a less noisy image than with standard Doppler, and also gives better assessment of slow flow with less angle dependence for direction and velocity.
Motorized imaging devices are being used increasingly in musculoskeletal applications. The most popular one is the high frequency ultrasound machine, forming images with frequencies in the range of 7 MHz to 15 MHz. The frequencies used are at the edge of the range for medical ultrasound (which is 2 MHz to 20 MHz). The advantage of high frequency ultrasound is that it gives the best resolution images of superficial structures. Unfortunately, the images are degraded more than with clinical lower frequency devices because of higher scatter from the tissues, but still remains impressive.
Electromyography (EMG)
EMG results are used to assist in the management of the condition being tested for. Certain results may allow the surgeon to defer unnecessary surgery at that point in time, or may allow for medical management of the condition in specific ways. An example of this is seen in the case of Total Knee Arthroplasty, where it has been shown at SMGH that patients with severe knee osteoarthritis, who are candidates for TKA, are best referred to the surgeon with better physical function and health. For those patients with expected post-operative treatment management, they may benefit from increased operative delay or alternative managed care. This is particularly valuable information when managing higher risk patients with conditions such as diabetes or in the case of potential cardiac surgery patients.
Electromyography is defined as a diagnostic procedure that evaluates activity in muscle tone and weakness that utilizes an electromyograph, which records the electrical activity in skeletal muscles. According to Dr. Kevin Lee from Mount Elizabeth Hospital, this test is required to understand the EMG part and the nerve conduction, in order to determine why certain muscles are not being activated or are weak.
Collaborative Approach to Knee Pain Diagnostics in Singapore
If there is persistent swelling or a known meniscal or ligament tear, usually surgery might be required and the best outcome is usually obtained if the patient is able to quickly consult the orthopedic surgeon.
Internists can regularly treat most injuries with medication and rest alone. However, sometimes referral to a specialist is required. If there is a suspicion of fracture, especially a stress fracture, an early referral could be best. If physiotherapy is not progressing as expected, or symptoms continue to recur, internal medicine doctors will commonly refer to a sports medicine physician who will be able to do a direct or guided injection to treat a secondary problem in an attempt to allow rehabilitation of the first injury.
Because the term “a picture tells a thousand words”, carrying out clinical radiographs and MRI are quickly becoming a standard “must do” for many knee conditions. This may require a radiologist to carry out a guided injection to substantiate a diagnosis.
In Singapore, knee pain diagnosis is becoming an increasingly multidisciplinary event. Regular diagnosis might solely contain the background and physical examination as a result of this already provides ample data to determine the problem for most comfortable tissue injuries. Nevertheless, with rising sub-specialty fields, the rising development is to search for affirmation of medical diagnosis and to determine the most suitable potential remedy.
Multidisciplinary Team Evaluation
The orthopaedic surgeon may then request investigation of the knee’s internal structures by a musculoskeletal radiologist to confirm the diagnosis. This may involve an ultrasound scan or an MRI. An ultrasound is useful for the dynamic assessment of structures such as tendons and ligaments. MRI is more expensive but has the advantage of being better able to visualize all different tissues within the knee and is considered the gold standard for imaging knee pain. This will aid in the diagnosis and a change of management in more than half of cases and is useful to monitor progress of the condition.
A study based on the diagnosis and treatment of knee pain at the National University Hospital in Singapore revealed interesting data on the reasons behind such referrals. The significant disparity between treatment strategies of orthopaedic surgeons and rheumatologists. Orthopaedic surgeons often found the advice of a rheumatologist compelled them to change their diagnosis and management in fifty-seven percent of cases, indicating that their diagnosis would have been incorrect if the patient had not been referred to the rheumatologist. This supports the theory that clinical symptoms and signs in many non-traumatic knee conditions are too often non-specific, resulting in an inaccurate diagnosis of the cause of the pain.
Multidisciplinary team evaluation is the first step in the knee pain diagnostics. The team consists of an orthopaedic specialist, a rheumatologist, and a musculoskeletal radiologist. When a patient presents with knee pain, an orthopaedic surgeon will initially evaluate the knee to determine the underlying cause of the pain. In the event of trauma with displaced bones, a fracture, or a torn ligament, treatment by the orthopaedic surgeon may be necessary. In non-traumatic cases where the exact cause of pain is unclear, the patient may be referred to a rheumatologist.
Patient History and Symptom Analysis
A good diagnosis is a very important part of good medicine. It can help to confirm the problem is indeed a knee problem, and not a problem referred from the lower back. It can give an accurate analysis of the type of knee problem that is occurring, and often give a very good indication of how to treat the problem. Many treatment options and exercises are specific to a particular diagnosis, and so getting the right one is very useful. Finally, a good diagnosis will give some idea of the prognosis of the problem. This is important as it gives realistic expectations to the patient about their progress, and it is a crucial part of a decision-making process regarding which treatment option to take. Reaching a good diagnosis is often difficult. This is due to the fact that many knee problems may have very similar signs and symptoms, but require very different treatments. Also, many chronic knee problems will have an acute exacerbation. Diagnosing the acute injury is not much use if the problem that caused it is not identified and rectified. Often people have several problems in one knee. These factors can sometimes make the history and symptoms quite complicated. Add to this the fact that many people have a poor understanding of medical problems, and in this case, the knee! This all makes the diagnostic process quite challenging. Many different health professionals are involved in the assessment of knee problems. These can include GPs, rheumatologists, orthopedic surgeons, physiotherapists, and other allied health professionals. For many knee problems, one of the key ways to identify the diagnosis is using imaging techniques such as X-ray, MRI, or ultrasound scans. However, the most important part of the diagnosis will often be the initial patient history and symptoms assessment.
Treatment Planning and Follow-up
In general, the aim of all treatment planning and review in the team’s approach is to optimize patient outcome. This is in terms of relieving pain, restoring normal function and quality of life, and preventing future recurrence of the knee problem. In order to measure treatment outcome, the knee assessment tools used during the initial phase of the diagnostic process can be reapplied at follow-up to compare changes in the patient’s knee condition.
Follow-up varies depending on the diagnosis and planned treatment. Patients will be reviewed in clinic following diagnostic tests such as x-rays and MRI. If a prolonged course of physiotherapy is the planned treatment, then review may not be until the end of physiotherapy. For simple isolated problems such as a meniscal tear with a good prognosis, review may take place following surgery in order to ensure that the knee has returned to full function. At the opposite end of the spectrum are patients with complex multifactorial problems such as arthritis. Follow-up for such conditions may be a prolonged period involving various different treatment steps, and the aim will be to prevent surgery if possible.
Details of the diagnosis and treatment plan are usually sent to the patient’s GP and other specialists involved in the patient’s care. This is important because accurate communication aids effective treatment and helps to avoid duplication of investigations and treatment.
Once a diagnosis has been made, a meeting is arranged between the patient and the team members involved in order to explain the diagnosis and determine the treatment plan. The exact nature of the knee problem, the patient’s occupation, expectations from the knee, and the presence of other medical problems are all taken into consideration when planning treatment. For many knee problems, there is more than one form of treatment. For example, the patient may be offered a choice between some sort of keyhole surgery and non-operative treatment. In this situation, the pros, cons, and success rates of different treatment options will be discussed with the patient in order to reach a joint decision.
Collaborative approach to knee pain diagnostics in Singapore: Multidisciplinary team evaluation, patient history and symptom analysis, treatment planning and follow-up.