KNEE Structured oral examination question2: Meniscus – basic science
KNEE Structured oral examination question2: Meniscus – basic science
EXAMINER: Tell me about the anatomy and function of the meniscus.
CANDIDATE: The menisci are crescentic cartilaginous structures interposed between the tibia and femoral condyles. They are triangular in cross-section. The peripheral borders are attached to the joint capsule. The medial meniscus is nearly semicircular with a wider posterior than anterior horn. This is attached anterior to the ACL insertion while the mid aspect is firmly attached to the deep MCL. The lateral meniscus is nearly circular with a larger surface than medial meniscus. The posterior horns of both menisci attach to the posterior intercondylar eminence. The attachment of the lateral meniscus to the capsule is interrupted by the popliteus tendon. Due to the loose attachment to the capsule, the lateral meniscus has twice the excursion of the medial meniscus. The anterior horns of both menisci are connected by intermeniscal ligaments.
Histologically, the menisci have an extracellular matrix composed mainly of water (70%) and primarily type 1 collagen fibres (60%), proteoglycans, elastin and glycoproteins.The main cellular component is the fibrochondrocytes that synthesize and maintain extracellular matrix. The blood supply to the meniscus comes from the lateral, middle and medial geniculate vessels with 20–30% of the peripheral portion being vascular. The main functions of the menisci are load transmission with estimated 50% in extension and 85% in flexion, joint conformity and articular congruity, distribution of synovial fluid aiding nutrition and joint lubrication. The menisci also have proprioceptive function, act as shock absorbers and prevent soft tissue impingement during joint motion.
EXAMINER : What are the vascular zones of menisci?
CANDIDATE: The menisci are relatively avascular structures with peripheral blood supply from the premeniscal capillary plexus formed by branches from lateral and medial geniculate vessels. Studies have shown that the degree of peripheral vascular penetration is 10–30% of medial meniscal width and 10–25 % of lateral meniscal width. This gives rise to the three zones of meniscal vasculature from peripheral to central, namely red– red, red–white and white–white. Therefore, peripheral tears are suitable for repair while central tears are not suitable due to lack of healing capacity.
Arnoczky SP, Warren RF. Microvasculature of the human meniscus. Am J Sports Med 1982;10:90–95.
EXAMINER: These are images belonging to a young professional footballer. What can you see? (Figure 3.2.)
CANDIDATE: This is a T2-weighted MRI of the knee showing sagittal and coronal images. There is absence of ‘bow tie sign’ of the medial meniscus and there is ‘double PCL sign’ suggestive of bucket-handle tear of medial meniscus.
EXAMINER: How would you manage this patient?
CANDIDATE: I would start by taking a detailed history and clinical examination ... [Examiner interrupts]
EXAMINER: How would you treat this patient? [Examiner getting impatient]
CANDIDATE: I would offer this patient EUA, arthroscopy, repair or excision of bucket-handle tear.
EXAMINER: Good. Are you aware of any meniscal repair techniques?
CANDIDATE: The four main meniscal repair methods are open repair, inside out, outside in and all inside. The ‘outside in’ method is versatile and safe. [Examiner interrupts again] EXAMINER: Let’s move on ...
KNEE Structured oralexamination question2: Meniscus – basic science
EXAMINER: Tell me about the anatomy and function of the meniscus.
CANDIDATE: The menisci are crescentic cartilaginous structures interposed between the tibia and femoral condyles. They are triangular in cross-section. The peripheral borders are attached to the joint capsule. The medial meniscus is nearly semicircular with a wider posterior than anterior horn. This is attached anterior to the ACL insertion while the mid aspect is firmly attached to the deep MCL. The lateral meniscus is nearly circular with a larger surface than medial meniscus. The posterior horns of both menisci attach to the posterior intercondylar eminence. The attachment of the lateral meniscus to the capsule is interrupted by the popliteus tendon. Due to the loose attachment to the capsule, the lateral meniscus has twice the excursion of the medial meniscus. The anterior horns of both menisci are connected by intermeniscal ligaments.
Histologically, the menisci have an extracellular matrix composed mainly of water (70%) and primarily type 1 collagen fibres (60%), proteoglycans, elastin and glycoproteins.The main cellular component is the fibrochondrocytes that synthesize and maintain extracellular matrix. The blood supply to the meniscus comes from the lateral, middle and medial geniculate vessels with 20–30% of the peripheral portion being vascular. The main functions of the menisci are load transmission with estimated 50% in extension and 85% in flexion, joint conformity and articular congruity, distribution of synovial fluid aiding nutrition and joint lubrication. The menisci also have proprioceptive function, act as shock absorbers and prevent soft tissue impingement during joint motion.
EXAMINER : What are the vascular zones of menisci?
CANDIDATE: The menisci are relatively avascular structures with peripheral blood supply from the premeniscal capillary plexus formed by branches from lateral and medial geniculate vessels. Studies have shown that the degree of peripheral vascular penetration is 10–30% of medial meniscal width and 10–25 % of lateral meniscal width. This gives rise to the three zones of meniscal vasculature from peripheral to central, namely red– red, red–white and white–white. Therefore, peripheral tears are suitable for repair while central tears are not suitable due to lack of healing capacity.
EXAMINER: These are images belonging to a young professional footballer. What can you see? (Figure 3.2.)
CANDIDATE: This is a T2-weighted MRI of the knee showing sagittal and coronal images. There is absence of ‘bow tie sign’ of the medial meniscus and there is ‘double PCL sign’ suggestive of bucket-handle tear of medial meniscus.
EXAMINER: How would you manage this patient?
CANDIDATE: I would start by taking a detailed history and clinical examination ... [Examiner interrupts]
EXAMINER: How would you treat this patient? [Examiner getting impatient]
CANDIDATE: I would offer this patient EUA, arthroscopy, repair or excision of bucket-handle tear.
EXAMINER: Good. Are you aware of any meniscal repair techniques?
CANDIDATE: The four main meniscal repair methods are open repair, inside out, outside in and all inside. The ‘outside in’ method is versatile and safe. [Examiner interrupts again] EXAMINER: Let’s move on ...