Knee Structure & Disorders

1. Knee Structure & Disorders

2. Outline • Structure • Skeletal • Soft tissue • Ligaments • Menisci • Bursae • Muscles • Movement • Exam • Disorders • Aspiraton/injection

3. Knee: Structure • Complex diarthrodial joint • Highly modified hinge joint • Compartments • Medial tibiofemoral • Lateral tibiofemoral • Patellofemoral

4. Knee: StructureSkeletal • Distal femur • Medial condyle • Lateral condyle • Intercondylar notch • Proximal tibial plateau • Medial condyle • Lateral condyle • Intercondylar eminence Hyaline Cartilage

5. Knee: StructureSkeletal • Patella • Largest sesamoid bone in the body • Articulates with the trochlea of the distal femur • Only engages the femur when knee flexed > 30° • Enhances active extension • Subject to magnified contact forces 8x body weight • Patellar articular cartilage is the thickest in the body – up to 7mm!

6. Knee: StructureStabilizers • Ligaments • Menisci • Bursae • Muscles • Joint capsule

7. Knee: StructureLigaments • Medial collateral ligament (MCL) • Superficial & deep • Medial epicondyle of the femur  10cm below joint line • Resists valgus stress across the knee • Provides secondary rotational stability

8. Knee: StructureLigaments • Lateral collateral ligament (LCL) • Lateral femoral condyle  posterior fibular head • Primary restraint to varusknee stresses

9. Knee: StructureLigaments • Anterior cruciate ligament (ACL) • Anteromedial bundle • Taut in knee flexion • Posterolateral bundle • Taut in knee extension • Resists excessive anterior translation and internal rotation of the tibia relative to the femur

10. Knee: StructureLigaments • Posterior cruciate ligament (PCL) • Anterolateral bundle • Taut in knee flexion • Posteromedial bundle • Taut in knee extension • Prevents excessive posterior translation of the tibia

11. Knee: StructurePosterolateral (PLC) • Area of major instability • Prevent • Excessive external rotation • Varus angulation • Posterior translation of the tibia

12. Knee: StructureMenisci • Crescentic disks of fibrocartilage • Deepen/stabilize the tibiofemoral articulations • Distribute the weight bearing load

13. Knee: StructureMenisci • “red zone” • Peripheral third • Vascularized • Potential to heal • “white zone” • Central third • Avascular • Minimal healing • “red/white zone” • Limited healing

14. Knee: StructureMenisci • Lateral meniscus • Nearly circular • Loose peripheral attachments • Greater motion in specific movements • Medial meniscus • Semi-circular • Close attachments to bone, medial joint capsule, and MCL

15. Knee: StructureBursae

16. Knee: StructureMuscles • Quadriceps - extensors • Rectus femoris • Vastus medialis • Vastus lateralis • Vastus intermedius • Medial and lateral patellar retinacula • Vastus medialis obliquus – restrains lateral patellar subluxation

17. Knee: StructureMuscles • Hamstrings – flexors • Medial • Semimembranosus • Semitendinosus • Lateral • Biceps femoris

18. Knee: StructureMuscles • Iliotibial (IT) band • Stabilize the lateral side of the knee • Accessory extensor or flexor of the knee • Pesanserinus • Gracilis, sartorius, semitendinosus • Weak knee flexors • Internal rotators • Patellar tendon

19. Knee: StructureTibiofemoral motion • Transfer and dissipates weight-bearing load • Mid-point of weight-bearing axis • Movement • Flexion & extension • Arc from 0-135° • Secondary movement • “Roll-back” • Rotation

20. Knee: StructurePatellofemoral motion • Augment moment arm of the extensor mechanism • Patellofemoral “tracking” • Q-angle • Measure of balance of medial and lateral forces on the patella

21. Knee: StructurePatellofemoral motion • Q-angle • Angle between line from ASIS to center of patella and another line from tibial tubercle • Normal • Men -- 13° • Women – 18° • Abnormal >20°

22. Knee: ExamHistory • Patient demographics • Age** • Pain characteristics • Onset, location**, duration, severity, quality • Mechanical symptoms • Effusion • Mechanism of injury • Back or hip symptoms • History of inflammatory arthritis or crystalline arthropathy

23. Knee: ExamObservation • Gait • Skin changes • Muscle atrophy • Quadriceps • VMO • Alignment • Valgus or varus • Normal - 7° of valgus

24. Bursitis Effusion “ballottement test” 10-15 ml of fluid “bulge sign” 8-10 ml of fluid Extensor mechanism Flex knee to 90° Active extension Other superficial structures Posterior palpation Medial and lateral joint line Knee: ExamPalpation

25. Knee: ExamRange of motion • Flexion-extension arc • 0-135° • Hyperextension or genurecurvatum • Up to 10° • Active vs. passive • Patellofemoral • Q angle • “J-sign” • Crepitus

26. Knee: ExamLigament • Anterior Drawer ACL

27. Knee: ExamLigament • Lachman test • Knee flexed to 30° • Physician stabilizes distal femur with one hand • Physician grasps proximal tibial in the other hand and attempts to sublux the tibia anteriorly • Positive Lachman = lack of clear end point • High positive predictive value ACL

28. Knee: ExamLigament ACL • Pivot-shift test • Positive test = palpable clunk in the knee at 30° of flexion

29. Knee: ExamLigament PCL • Posterior sag test

30. Knee: ExamLigament PCL • Posterior drawer test • Positive test = anterior tibia displaces posteriorly until it is flush with distal femoral condyle

31. Knee: ExamLigament • Medial and lateral collateral ligaments LCL MCL

32. Knee: ExamLigament PLC • Dial test • Knee flexed to 30° • External rotation stress • Positive = difference of >10° laxity • Repeat test with knee flexed to 90° • (+) test at 30° • Isolated PLC injury • (+) test at 30° and 90 ° • PCL + PLC disruption

33. Knee: ExamMeniscus • McMurray test • Medial and lateral menisci • Positive test = thud or click or reproducible pain

34. Knee: ExamMeniscus • Apley Grind test • Positive test = pain or clicking with internal or external rotation

35. Knee: ExamRadiographs • Anteroposterior view • Lateral view • Merchant’s view • Patellofemoral joint • Notch or tunnel view • Postero-anterior view with knee flexed to 40-50° • Osteochondritis dissecans • Weight bearing view • Osteoarthritis

37. Knee: Disorders

38. Knee: Disorders

39. Knee: Disorders

40. Knee: Disorders

41. Knee: DisordersOsgood-Schlatter disease • Traction apophysitis of the tibial tuberosity • Boys age 10-14 • Pain over the tibial tuberosity • Jumping activities • Resisted extension • Treatment nonoperative • Usually self resolves • Avoid jumping activities • Sinding-Larsen-Johansson syndrome

42. Knee: DisordersOsteochondritis Dessicans • AVN of bone affecting the osteochondral junction of the epiphysis • Boys>>>girls • Knee most commonly affected • Pain and mechanical symptoms • Wilson’s test • Straightening internally rotated knee from a flexed position

43. Knee: DisordersOsteochondritis Dessicans • Radiographs • X-rays – tunnel view ** • CT • MRI • Treatment • No treatment • Conservative tx – activity limitation, PT • Operative tx • Microfracture and abrasion • Osteochondral allograft/autograft transfer (OAT) • Autologous cartilage implantation (ACI)

44. Knee: DisordersPatellofemoral disorders • Anterior knee pain • Imbalance between medial and lateral forces • High Q-angle • Atrophy of medial stabilizers • Contracture of lateral structures

45. Knee: DisordersPatellofemoral disorders • Apprehension test • Knee in 20° flexion • Patella manually subluxed laterally to reproduce symptoms of instability • Patella tilt test • Knee in 20° flexion • Lateral margin is flipped up • (+) test – patella cannot be tilted upward past horizontal

46. Knee: DisordersChondromalacia patellae • Anterior knee pain • 4 stages of severity • Stage I – softening and swelling of articular cartilage • Stage 2 – deep fissures extending to subchondral bone • Stage 3 – fibrillation of the articular surface • Stage 4 – loss of articular cartilage with exposed subchondral bone

47. Knee: DisordersMedial plica syndrome • Medial knee pain • Mimic medial meniscal tear • Irritation of the medial femoral condyle • Repetitive overuse • Conservative therapy

48. Knee: DisordersInjury

49. Exam Lachman Anterior drawer Pivot shift Radiographs Avulsion injuries of tibial spines Segond fracture MRI Treatment Low demand - no treatment Moderate demand – PT and knee brace Surgery Knee: DisordersACL injury

50. Knee: DisordersInjury