The Knee: Anatomy and Injuries

2 Joints at the Knee Tibiofemoral Joint – formed between the femur (femoral condyles), and the tibial plateau A HINGE JOINT Patellofemoral joint – formed between the patella and the femur A GLIDING JOINT

Skeletal Anatomy Femur proximal – head and neck of femur, greater trochanter distal – medial and lateral condyles and epicondyles

Patella – largest sesamoid bone in body Tibia – tibial plateau forms knee joint with femur The fibula is not a part of the knee joint

Muscles that move the knee and thigh The Quadriceps – Knee Extension 1. Vastus Medialis 2. Vastus Lateralis 3. Vastus Intermedius 4. Rectus Femoris – 2 joint muscle that also acts as a hip flexor

The Hamstrings- knee flexion 3 muscles: 1. Biceps Femoris 2. Semimembranosus 3. Semitendinosus

The Adductors (Groin) Adduct the thigh 1. Adductor Longus 2. Adductor Magnus 3. Adductor Brevis 4. Gracilis

The Sartorius: - flexes, abducts, and laterally rotates thigh - longest muscle in the body, “ tailor ’ s muscle ” - Crosses hip and knee joint

The Iliotibial Tract (IT Band) - neither a muscle or tendon, but a long, thick band of tissue that inserts into the lateral tibia (Gerdy ’ s Tubercle)

The Major Knee Ligaments 1. ACL – Anterior Cruciate Ligament 2. PCL – Posterior Cruciate Ligament 3. MCL – Medial Collateral Ligament 4. LCL – Lateral Collateral Ligament

The Cruciate Ligaments The major stabilizing ligaments of the knee ACL Runs from posterior femur to anterior tibia Prevents anterior displacement of tibia PCL Runs from anterior femur to posterior tibia Prevents posterior displacement of tibia

The Collateral Ligaments MCL: - Medial Collateral Ligament - Runs from medial femur to medial tibia - Prevents valgus force LCL: - Lateral Collateral Ligament - Runs from lateral femur to head of fibula - Prevents varus force

The Meniscus A “ c ” -shaped piece of fibrocartilage located in the knee joint between the femur and attached to the top of the tibia Cartilage = meniscus

Differences between medial and lateral Medial - larger and more C-shaped - more firmly attached to tibia - has attachments to MCL Lateral - smaller and more round or O-shaped - not firmly attached to tibia and LCL

Blood Supply to the Meniscus Mostly avascular – little or no blood supply Only the outer 20% has a blood supply * Does not have the ability to heal itself unless there is a small tear in the outer 20%

Functions of Meniscus 1. Stability 2. Shock absorption 3. Lubrication and nutrition 4. Allows adequate weight distribution

Normal Torn

Total Knee Joint Replacement Surgery to replace a painful damaged or diseased knee joint with an artificial joint (prosthesis) Artificial hip invented – first artificial knee in USA

The Knee Surgery Thin layer of bone removed from femur – thin metal replaces it Upper layer of tibia replaced with plastic Back of patella replaced with plastic Parts fastened with “ bone cement ”

Risks of Knee Joint Replacement Blood clots in large veins Infection Stiffness Implant Loosening/Failure - more of a problem in younger patients

Knee Injuries and Conditions

Genu Valgum: “ knock knees ”

Genu Varum: “ bowlegs ”

Genu Recurvatum: hyperextension of the knee joint

Patellar Tracking Disorder When your patella is out of balance or the patellar cartilage is damaged, you can have knee pain while climbing stairs, running, standing up from a bent-knee position, squatting, or even sitting for a period of time. This kind of pain, called anterior knee pain or patellofemoral pain syndrome, is sometimes caused by a common kneecap problem known as patellar tracking disorder.

Causes Quadriceps weakness Tendon and muscle tightness in the leg, foot, or hip areas Improper athletic technique or training A blow to the kneecap Excessive body weight, which overstresses the knee joint. Genetics

Genetics (cont.) - An excessively long patellar tendonpatellar tendon - patellar shape, hip structure, or a shallow femoral groove for the patella to glide along

Patellofemoral Disorders Problems with patella – most common cause of knee pain Anatomy: - Patella is a sesamoid bone formed in Quad tendon - Patellofemoral joint – patella and femur - Compression forces – <body weight during walking 2.5 x body weight during stairs

Patellar Tendonitis “ Jumper ’ s Knee ” Inflammation and degeneration of the tendon that connects the kneecap (Patella) to the shin bone (Tibia).

Chondromalacia A gradual degenerative change that occurs beneath the patella Caused by acute trauma, repeated microtrauma, or improper alignment of the patella in the trochlear groove Weak vastus medialis (VMO) can cause improper alignment Prevention: strengthen quads Minimize squats, downhill running, biking with low seat

Chondromalacia

Patellar Dislocation Dislocation usually occurs as a result of sudden direction changes while running and the knee is under stress or it may occur as a direct result of injury. Usually lateral

Rehab: strengthen quads, especially VMO to hold patella in place Each dislocation will damage cartilage which can eventually lead to traumatic arthritis

Osgood-Schlatter Disease 1. Painful swelling over tibial tuberosity (patellar tendon insertion) 2. Usually occurs between 9-13 years of age 3. Pain increases with activity

The Chopat Strap The Cho-Pat knee strap is an excellent product for those with a knee (patella) tracking problem. Worn by many athletes the chopat strap functions as the knee bends and straightens putting pressure on the tendon below the knee cap helping guide the knee cap in the proper groove. This improves tracking and assists in spreading pressure uniformly over the surface area. In addition, the strap elevates the knee cap slightly which relieves harmful pressure.

Iliotibial Band Friction Syndrome Occurs where IT Band rubs over femur at the knee joint Common in running (esp. downhill) or any activity with repetitive flexion Hills or stairs increase pain Lots of IT Band stretching

Popliteal Cyst “ Baker ’ s Cyst ” Fluid accumulation in posterior knee (popliteal space) Patient usually complains of a mass behind the knee

Prepatellar Bursitis “ Housemaid ’ s Knee ” Tender swelling over the kneecap (prepatellar bursa)

Pes Anserine Bursitis Pes anserine bursitis is an irritation or inflammation of a bursa in your knee. The pes anserine bursa is located on the inner side of the knee just below the knee joint. Tendons of three muscles attach to the shin bone (tibia) over this bursa

Knee Sprains

ACL Sprain Not most commonly torn knee ligament Higher incidence in females 2-8 times more likely Males = contact Females = noncontact

ACL Sprain 1. MOI: twisting of knee forced hyperextension lateral blow to knee *foot must be firmly anchored to playing surface 2. May describe a “ pop ” in knee 35% - 65% of people 3. Knee fills with blood quickly Hemarthrosis 4. Usually immediate loss of motion 5. Knee feels unstable

Anterior Drawer Test: examiner attempts to slide the tibia forward which may indicate a torn ACL ligament

ACL Sprain Who needs surgery? - Activity level? - Level of Competition - Age?

ACL Surgery Arthroscopic Graft options Patellar Tendon Semitendinosus Gracilis Cadaver Synthetic

PCL Sprain 1. MOI: excessive hyperextension hyperflexion tibia forced posteriorly (blow to front of knee) “ dashboard knee ” Possibly 90% of all PCL injuries due to motor vehicle accidents?

2. Mild hemarthrosis 3. Posterior knee pain 4. Walk with knee slightly flexed, avoid full extension 5. Posterior sag of tibia 6. Surgery?

MCL Sprain MOI: Blow to the outside of the knee = Valgus Force Possible overuse – breaststroke in swimmers Commonly associated with meniscal injuries – attached to medial meniscus No surgery

MCL Sprain

Valgus Stress Test: tests for injury to the MCL ligament

LCL Sprain MOI: Blow to inside of the knee – Varus force Grade III tear may require surgery

Varus Stress Test: tests for injury to the LCL ligament

Injuries to the Meniscus 1. MOI: Rotation of the knee as the knee extends during rapid cutting or pivoting

2. Signs and Symptoms: - pain - joint line tenderness - catching or locking - knee buckling or giving way - swelling - incomplete flexion - clicking on stair climbing

3. Surgery? Meniscectomy: removal of the meniscus - Total meniscectomy = osteoarthritis Depends on location of tear, type of tear, and blood supply

Types of Meniscal Tears - bucket handle - Flap tear - Transverse tear - Horn tear

Tests for Meniscal Tears Apley ’ s Compression

“ The Unhappy Triad ” Tear of the medial meniscus, anterior cruciate ligament (ACL), and medial collateral ligament (MCL)