Knee and Thigh: Understanding the Structure and Function of the Knee Joint

1. chapter23 Knee and Thigh

2. The Knee • The knee is one of the most frequently injured joints in athletics. • The forces applied to it during sport activities are complicated by the fact that there are two long lever arms on either end of the joint, making it a joint that is susceptible to injury. • Stability comes from ligaments and muscles.

3. Knee Structure • Two joints: tibiofemoral joint and patellofemoral (PF) joint • Capsule: resting = 20°-25° flexion; closed = full extension, external rotation (ER) • Ligaments: medial collateral (MCL), lateral collateral (LCL), anterior cruciate (ACL), posterior cruciate (PCL) • MCL: restricts valgus stresses, ER • LCL: restricts varus stresses, internal rotation (IR) • ACL, PCL: restrict AP stresses; taut during IR (continued)

4. Knee Structure (continued) • Neuroreceptors: in capsule, ligaments • 1° stability: ligaments; 2°= capsule, muscles • Medial/lateral meniscus: fibrocartilage screw home mechanism: flexion  extension WB: IR femur NWB: ER tibia • Muscles: quadriceps and hamstring groups, popliteus

5. Patellofemoral Joint • Resting position: full extension • Closed position: knee flexion • Patella must glide freely for full knee motion to occur • Patella excursion is 5-7 cm • Inferior pole of patella lies at tibiofemoral joint margin • Contact between femur and patella changes through range of motion (ROM) (continued)

6. Patellofemoral Joint (continued) • Joint reaction force: compressive force = PF quadriceps muscle and tendon resultant vector force • Contact pressure: ratio between PF joint reaction force and contact area • In closed kinetic chain, as knee flexes, contact area and compressive force increase • Force  is greater than surface , so compression increases in WB with ROM increases

7. Figure 23.1

8. PF Compressive Forces • Greatest patellofemoral compressive forces occur in 60°-90° positions. • Closed kinetic chain (CKC): 0° to 30° produces minimal PF stress. • Open kinetic chain (OKC): <20° (without weights) produces minimal PF stress. (continued)

9. PF Compressive Forces (continued) • Distally attached cuff weights produce maximum patellofemoral compressive forces at 35°-45°. • Greatest tibiofemoral shear force: 15°-30°. • Machine resistance applied at the ankle reaches maximum patellofemoral compressive forces at 90°.

10. Figure 23.4

11. Patellar Malalignments • Patella alta: patella higher than its normal position in the patellofemoral groove • Patella baja: patella lower than its normal position in the patellofemoral groove

12. Q-Angle • = The angle that is formed by a line from the anterior superior iliac spine (ASIS) to the middle patella and a line from the middle patella to the tibial tubercle • Normal Q-angle 10°-15° • Can change from weight bearing to non-weight bearing • Disputable evidence that it is larger in women because of pelvic structure • Pronation or a weak vastus medialis oblique (VMO) can increase the Q-angle

13. Figure 23.2

14. Leg Alignment • Excessive rearfoot pronation influences the patella’s alignment. • Since the lower extremity works as a CKC during most functions, malalignment in one segment affects or causes compensatory changes in another segment.

15. Factors Affecting Postinjury Strength • Edema: inhibits quadriceps function • Pain: causes reflex withdrawal inhibition • Antalgic gait: causes weakness throughout lower extremity

16. Rehabilitation Concepts • Extensor lag: in presence of full passive knee extension, incomplete active knee extension is secondary to quadriceps weakness. • Quadriceps force required for last 15° of extension is twice as great as for other ranges of motion because of the muscle’s reduced mechanical and physiological advantage. (continued)

17. Rehabilitation Concepts (continued) • ACL stress in weight bearing is at least 0°-60° • ACL stress in non-weight bearing is greatest at 30°-60° and least at 60°-90° 0-60° 60-90°

18. Figure 23.3

19. Knee Bracing • ACL braces provide stability during low-stress loads but not during functional loads. • Knee braces may provide proprioceptive feedback. • Types: prophylactic for prevention, rehabilitative for protection, functional for stability • Custom and off-the-shelf

20. Therex Progression • Dictated by tissue healing and response to exercise stress • Range of motion via exercise, joint mobilization, soft-tissue mobilization • Strength exercises with low-level resistance initially (continued)

21. Therex Progression (continued) • Balance with bilateral support, progressing to unilateral static and then dynamic activities • Agility activities • Functional activities • Sport- and activity-specific exercises

22. Soft-Tissue Mobilizations • Massage for edema, spasm • Deep-tissue releases for adhesions • Foam roller on tensor fascia latae (TFL), quadriceps or deep-tissue massage • Trigger point releases: • Quadriceps: patella from rectus femoris or vastus medialis • Popliteus: posterior knee pain • TFL: lateral thigh

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30. Figure 23.7a

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37. Figure 23.13a

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40. Figure 23.13d

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45. Figure 23.18

46. Flexibility • Short-term: active versus passive • Prolonged • Age of scar tissue • Continuous passive motion (CPM) machines immediately following surgical repair

47. Figure 23.19

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50. Figure 23.23