CAUSES:Mechanical overload of the patellofemoraljoint.a) Malcongruence - patellofemoral surfacesb) Malalignment – extensor mechanism- weakness of vastus medialisSingle injury – damage to articular surface
PATHOLOGYDegeneration of articular cartilage-PrecipitantChanges in articular cartilage + subchondral bone1.Cartilage N appearance with only biochemical changes but boneshows reactive vascular congestionOR2.Cartilage softening/fibrillation with or without subarticularintraosseous hypertensionFibrillation usually on undersurface of the patella at the jn. of medialand odd patellar facet /median ridge confined to superficial zonesand heals spontaneously.NOT A PRECURSOR OF OA!
Lateral Articular surface involvement-usuallycongenital tightness of lateral quadricepsexpansion„Ficat’s hyperpression zone syndrome’OrExcessive Lateral Pressure SyndromePredisposes to OALateral Release for prophylaxis
CLINICAL FEATURES• Introspective teenage girl or athletic young adult• Flat foot / Knock kneed athletes• Spontaneous Pain in front of knee/ beneath the kneecap• Maybe h/o recurrent displacements/injury• Aggravated by activity/climbing downstairs/standing after prolonged sitting with kneesflexed• Both knees• Swelling-give way-catching(not true locking)• Grating/grinding sensation when knee is extended
SignsAppears N kneeMalalignment/tilting of patellaQuadriceps wastingEffusionCrepitus on moving the kneeTenderness under the edge of the patellaSmall high patellaIn severe cases a/w Patella Alta“Theatre sign”
Press patella against femur to elicit pain and asking patientto contract the quadriceps first with central pressure thencompressing the medial facet and then the lateral facetApprehension test + implies previoussubluxation/dislocation.Patellar tracking with pt seated at edge of the couch, flexingand extending knee against resistancePatellar alignment gauged by Q angle-angle subtended bythe line of quadriceps pull and the line of patellar ligament.Should not exceed 20 degreesStructures around knee and hip examined r/o referred pain
STAGESI: swelling and softening of the cartilageII: fissuring within the softened areasIII: fasciculation of articular cartilage almost tolevel of subchondral bone;IV: destruction of cartilage with subchondral boneexposed
Grading (Bentley 1992)• Grade I: area <0.5 cm diameter• Grade II: Area 0.5 – 1.0 cm diameter• Grade III: area 1.0 – 2.0 cm diameter• Grade IV: area >2 cm diametera: softening, swelling/fibrillation of cartilageb: Full thickness cartilage loss to bone
IMAGING• X Rays- skyline viewlateral view with knee half flexedTangential views at 30, 60 and 90 degrees offlexionBest seen on slightly overexposed lateral X rayAxillary radiograph determines which facet is involvedMost accurate to measure malpositon CT/MRI with knee infull extension and varying degrees of flexion.
• Diagnosis made only on Arthroscopy or surgery• Arthroscopy is useful to r/o other causes of anteriorknee pain. Also to know presence and extent of thelesion and probing of patella with soft probe• Gauge patellofemoral congruence, tracking andalignment
Preventive MeasuresShort-arc extensionsDone sitting up or lying down.Rolled-up towel to support the thighkeep leg and foot in the air for 5 seconds.Lower foot as knee is bent slowly.Repeat 10 times for each leg, twice a day.
Straight-leg raisesDone lying down.Lift whole lower limb at the hip with the knee extendedkeep it up in the air for 5 seconds. Then lower slowly.Repeat 10 times for each leg, twice a day.
Quadriceps isometric exercisesDone sitting up, with legs extended in frontTighten quadriceps muscles by pushing the kneesdown onto the floor.Hold for 5 seconds.Repeat 10 times each leg, twice a day.
Stationary bicyclinglow tension setting improves exercisetolerance without stressing the knee.Seat should be high enough so that the leg isstraight on the down stroke.Start with 15 minutes a day and work up to 30minutes a day.