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Knee joint applied mechanics - an overview
- 2. • Dissimilar surfaces • Little/No inherent bony stability • May be cause of additional instability if fractured • Peroneal nerve • More commonly injured • Tethered around the fibular neck • Mechanism of injury • Tension (Varus ± hyperextension, Translation (Anterior /Posterior dislocation) • Direct impact • Iatrogenic (aggressive varus/hyperextension • Tibial nerve
- 3. • Direct/indirect inj-due ti sports such as jogging,skating,skiing,football,tennis. • Structures involved-menisci,lig,bones,musculo- tendinous structures. • Blow to lateral aspect of knee jt –valgus stress- tearing of lig restraining val stress. • Forced hyper extension of knee- tear of post lig. • Low level force-disrupt lig weakened by aging,disease,immobilization,steroids or vascular insufficiency. • Cyclic loading may also affect visco elasticity and stifness.
- 4. • Isolated – only one element injured • Combined knee injury – two elements injured (e.g. ACL + MCL) • Complex trauma of the knee joint– three or more elements injured KNEE INJURIES
- 5. • The medial meniscus is more movable than the lateral. It could be injured during the internal rotation of the lower leg accompaigned by knee flexion. • Axial rotation in flexed knee occurs with med meniscus as pivot point. • The more rididly attached medial meniscus may tear under sudden load. • The lateral meniscus could be injured during the external rotation of the lower leg accompaigned by knee flexion KNEE INJURY MECHANISMS
- 8. ACL (anterior cruciate ligemant) TEAR
- 9. Knee Joint Injuries ACL rupture - most commonly damaged ligament of the knee. Many sports apply external and internal forces to knee. Often caused by some type of cutting, twisting or hyperextension. Unlike the MCL & PCL, the ACL does not have the capacity to heal. Once injured, it does not reconstitute as a functional entity.
- 10. ACL Tear
- 11. Knee Joint Injuries ACL injury rates are 4 to 8 times higher in female athletes who take part in soccer, basketball, track, and softball (compared to baseball) than male athletes. Sagittal plane landing mechanics may play less of a role in gender-related ACL injury than frontal and transverse plane mechanics. Effect of fatigue on knee valgus and internal rotation may have more consequence on female than male.
- 12. SYMPTOMS • Pain • Loss of function • Swelling, bruising • Muscle atrophy • Difficulty bearing weight
- 13. Knee Joint Injuries Meniscus tearing – frequently caused by planting foot during weight bearing while body undergoes rotation. Symptoms include pain, accompanied by locking or buckling of the joint. Collateral ligament sprain - one of the most frequent knee injuries. Usually caused by blow to lateral knee. Deep fibers of medial collateral ligament attach to medial meniscus, so could disrupt meniscus too.
- 16. Knee Joint Injuries Chondromalacia - affects the articulating cartilage on the interior surface of the patella. Possibly caused by incongruence between patella and femur. Symptoms include pain, swelling and a grating sensation. Osgood Schlatter Disease - usually affects children and is caused by repeated usage of the knee extensors. This overuse results in a tearing or avulsion at the epiphysis of the tibial tuberosity. Symptoms include pain, swelling, hemorrhage.
- 18. Knee Dislocation– Multiligamentous Injury • Disruption of normal relationship of tibiofemoral joint • Usually requires the injury to 2 of the 4 major groups of ligaments
- 19. Classification – Injured Structures Schenck RC et al. 1992 V C N III L ACL / PCL / LCL+PLC MCL intact IV ACL / PCL / MCL / LCL+PLC III M ACL / PCL / MCL LCL+PLC intact Schenck 1992 II arterial injury nerve injury fracture dislocation Anatomic Classification of Knee Dislocations I single cruciate + collateral ACL + collateral PCL + collateral ACL / PCL collaterals intact
- 20. • Prolonged compressive and tensile forces- bursitis-prepatelar bursitis-housemaid’s knee. • Patellar plica-symptoms-pain with prolonged sitting, stair climbing and during resisted exs and snaping sensation. • During flexion-plica pressed under patella- inflammed.
- 21. Pathomechanics • May occur not only with high energy but also with low energy • Low energy • Athletic activity (more with contact sports) • Fall down stairs • Jump of the low height • High energy • Motor veh accidents • Fall from height
- 22. Pathomechanics • Progressive Hyperextension model Anterior dislocation • At around 30 degrees: tear of posterior CAPSULE happens • Followed by tear of PCL & ACL DISLOCATION • Around 50 degrees: rupture of POPLITEALARTERY noted
- 23. Pathomechanics • Cadaveric study • Combined cruciate ligaments injury in hyperextension • Low rate of strain-(100%/sec) midsubstance tear of PCL • High rate of strain (400%/sec) avulsion of PCL from femur • ACL: Mixed pattern of injury