chapter 23 Knee and Thigh

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.

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)

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

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)

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

Figure 23.1

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)

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°.

Figure 23.4

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

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

Figure 23.2

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.

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

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)

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°

Figure 23.3

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

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)

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

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

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Strength Can begin early even if knee is immobilized and non-weight bearing. Exercises for trunk, hip, and ankle should be included. Pain or swelling should not occur during or after exercise. Add exercises judiciously so can identify cause of inflammatory response.

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Proprioception and Functional Activities Program includes proprioceptive exercises aimed at restoring balance, agility, and coordination. See figure 23.46a-c. Functional exercises for the knee, which are similar to those for the hip and ankle, use hopping, running, and cutting as well as sport-specific drill and skill activities.

Figure 23.46a

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Figure 23.46c

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Figure 23.47b

Injury: Sprain Swelling occurs in 2-24 h ACL reconstruction: patellar tendon or hamstring graft Delayed versus accelerated rehab Strong gastrocnemius contraction avoided beyond 30° flexion in PCL sprains MCL injuries rarely surgically repaired Avoid patellofemoral pain

ACL Reconstruction Rehabilitation considerations Patient age Weight-bearing status Source of graft Must always keep in mind healing and maturity of graft

Meniscal Injuries Isolated meniscal tears are more likely to be degenerative. Lateral meniscal repairs have a better success rate than medial repairs. In the long run, meniscal repair is more beneficial than meniscectomy. Conservative versus accelerated rehab

Figure 23.49

Meniscal Repair Arthroscopic procedure Weight bearing is partial initially Avoid stressing meniscus in area of repair. Communication with surgeon is vital.

Patellar Injuries Patellar dislocations and subluxation Patella plica syndrome Osgood-Schlatter disease Patellar tendinitis patellofemoral stress syndrome = PFSS (PFPS) Tendon rupture

Patellar Dislocation Extreme pain, edema Disability prolonged if swelling is excessive Quadriceps strengthening important Inability to walk without assistive devices until full active knee extension is possible and patient ambulates without limping

PFPS Must identify and correct causative factors Must relieve muscle imbalances Effects of foot, hip, trunk Evaluate patellar alignment and tracking in weight bearing and non-weight bearing McConnell taping effective in relieving pain

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Strains and Contusions Hamstring strains—hamstring tightness often a predisposing factor Quadriceps strains—often due to jumping or sudden changes in direction Quadriceps contusions—first goal is to resolve pain and spasm and maintain flexibility (continued)

Strains and Contusions (continued) Myositis ossificans: causes non-neoplastic bone formation in the muscle Iliotibial band (ITB) syndrome: Overuse syndrome in middle- and long-distance runners Pain at 30° knee flexion when ITB is pulled over the lateral femoral epicondyle

Fractures Patella fracture: often result of a direct blow Tibial fracture: often due to torsion or compression forces Epiphyseal plate injuries of the proximal tibia or distal femur Occur in adolescents whose growth plates have not yet matured Can alter bone growth

Osteochondritis Dissecans Unknown etiology Affects femoral epiphysis in juveniles, femoral condyle in adults Bone flake in juvenile osteochondritis dissecans (OD), bone fragment in adult OD Knee pain, tenderness, quadriceps atrophy; catching, locking, or giving way Treatment and rehabilitation