Colin McHenry; Week 8 MED1022; Anatomy
Knee is largest synovial joint. It is a complex joint (more than 2 bones involved), can be problematic, cause of many problems. It has 3 translation movements, 3 rotation (usually don’t want translation). It is inherently unstable (flat tibia and round femoral surface). In full extension of leg, tibia rotates medially (popliteal ligament locks)
Don’t want AP translation, ML translation, vertical translation, rotation in coronal plane (abd-add)
Menisci improve congruence and absorb compressive loads. They do not cover entire surface of tibia, lunate shaped (convert load to loop stress) and are comprised mostly of fibrocartilage. The internal part of loop has no vascular supply, when torn to inside there are minimal chances of repair, medial more likely to tear (less flexible). Firmly attached to ligaments, medial is more attached, lateral moves more freely so not prone to injury. Because medial menisci is attached, it may tear.
PCL is stronger, outside synovial joint. Synovial cavity is complex, suprapatellar bursae is part of it, synovial membrane folds around cruciate ligaments. There is no capsule anteriorly (patella instead). Collateral ligaments- medial is bigger as force from lateral side more likely, bone is at an angle that makes the medial more prone.
Popliteal ligaments: oblique, arcuate, appear to be extensions of popliteal tendon, resist internal rotation, abduction. Popliteus can actively resist internal rotation, powers lateral rotation that ‘unlocks’ knee. Lateral dislocation of patella is more likely
Semimembranosus tendon fibres continuous with capsule fibres. Importance of muscles in joint stabilisation (not just knee)- muscles brace joint, unexpected loads cause more damage
There are 4 bursae anteriorally, 5 medially, 4 laterally, variable number posteriorly.
Pentadactlyl limb plan. Epipedials, proximal row, centralia (navicular), distal row is cuneiforms