What Is Articular Cartilage Defect/Lesion?
Articular cartilage lesion or defect is a common knee injury in athletes and other sportsmen. The injury is the outcome of repetitive trauma or overuse of the knee cartilage while playing. Since the natural morphology (built) of the cartilage is such that it has limited self-healing capacity. The symptoms of cartilage defect do not appear promptly since cartilage has no nerve supply. However, after some time, the cartilage defect leads to inflammation, pain, limited mobility, and non-smooth movement of the knee. The defect can range from being a form of one-spot injury called focal injury to complete cartilage tear up to the bone. The tear leads to the replacement of the fluid that acts as a lubricant in the otherwise healthy knee by a fibrous tissue that forms fibrocartilage.
The progression of the defect can lead to osteoarthritis of the knee in the worst-case scenario.
What Are the Different Types of Advanced Imaging Technologies for Diagnosing Knee Defects in Athletes, and How Are They Helpful?
Early intervention after signs are evident should be done at the highest priority. The diagnosis can be made on clinical signs and symptoms, too. However, the imaging techniques give a confirmed diagnosis and hence pose a better treatment plan.
After going through a complete medical examination, imaging provides a picture of tissues, cartilage, and bone within the knee. The imaging tests done include X-ray, MRI, and CT scan.
1. X-Ray:
X-rays have been the most common form of diagnostic tool that has been widely used by people all around the globe.
The basis for the diagnosis is the measurement of joint space. The conclusion for an articular defect on an x-ray is done by cartilage wholeness or the amount of tear in the cartilage by which joint space is measured. However, radiographs do not give findings of articular cartilage defect at the initial stage. Unlike other joints like the hip or shoulder, the joint space does not signify cartilage only but has a meniscus, too. Hence, X-rays have a high probability of giving false negative or false positive results.
Despite the odds, X-ray remains the best diagnostic for hyaline cartilage clarification, making this tool even better than MRI in this regard.
2. Diffraction Enhanced X-ray Imaging:
This is an advanced and new technique of x-ray in which a more clear picture of the articular cartilage is seen. The better visualization is attributed to the use of silicon crystals, which enables a more focused image of the cartilage. These findings are correlated to histopathological findings and clinical symptoms to get the confirmed diagnosis.
3. Ultrasound:
Unlike X-rays, ultrasound is not based on radiation but on sound ways. The Ultrasound helps to show the moments of internal organs as well as any fluid movement between the joint spaces.
Based on this, USG is used in the diagnosis of articular cartilage defects. Bone ultrasound is used to assess the bone thickness, elasticity, and strength of bone. The normal articular cartilage appears anechoic (i.e. appearing black on imaging test due to no sound waves reflecting back from fluid), and the margins are sharp. In articular cartilage defects, the sharpness of the margins is lost. The USG does not appear homogeneously anechoic in this condition. USG remains a valid diagnostic than histopathology in the diagnosis of articular cartilage defect.
4. MRI (Magnetic Resonance Imaging):
MRI has remained the most favorable, accurate technique of choice for physicians in the diagnosis of articular defects. It is a non-invasive procedure that shows soft tissue in high contrast and cartilage thickness with accuracy. Advancements in MRI techniques have resulted in giving important markers about disease progression as well as the outcome of repair sustenance after surgical repair.
The advanced techniques of MRI are
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Morphological Sequence- It determines the defect on the basis of size, depth, and location.
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Compositional Sequence - It determines the defect on the basis of biochemical changes that occur before structural changes. If the changes are detected earlier, it is possible to stop further progression of the defect, and in some cases, it is possible to reverse the disease as well.
Recent advances in MRI are
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T2 and T2* mapping.
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GdEnhanced MRI.
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Sodium MRI.
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T1p imaging.
5. Intragrtaed PET-MRI:
PET is a positron emission tomography, which is an investigation on a molecular level. PET and MRI are combined together to detect the defects in articular cartilage, which are the most accurate, and very initial changes in cartilage can be differentiated by this technique. The evaluation in this technique is done by using some radioactive materials that trace the cellular activity in the pathologies that are suggestive of joint inflammation and cartilage defect.
6. Computed Tomography (CT):
CT is used in patients where MRI is contraindicated. CT is an invasive technique where intra-articular contrast is injected that colors up the joint fluids and the ligaments. After injecting the contrast medium, the patient is asked to move the joint. The contrast is seen in the cartilage, and hence, the thickness and the defect in the cartilage are visible.
Types of CT done are
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Multidetector CT (MDCT).
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Weight-bearing CT.
Although CT is the least preferred diagnostic imaging used for knee defect injury, it offers some merits over MRI. CT is less time-consuming. It is more affordable and is an alternative for patients where MRI is contraindicated.
Conclusion
The articular cartilage defect in athletes is very common and needs a timely approach. If left untreated can cripple the athlete for a lifetime. It can lead to osteoarthritis at a young age. All imaging techniques, MRI in particular, have proposed the best diagnostic approach for better treatment and good prognosis of the condition.
