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Updated: Feb 25 2024

Articular Cartilage Defects of Knee

Images
https://upload.orthobullets.com/topic/3133/images/focal defect.jpg
https://upload.orthobullets.com/topic/3133/images/45 deg pa xr.jpg
https://upload.orthobullets.com/topic/3133/images/long leg xr.jpg
https://upload.orthobullets.com/topic/3133/images/dgemric.jpg
https://upload.orthobullets.com/topic/3133/images/mfx.jpg
  • summary
    • Articular cartilage defects of the knee comprise of a spectrum of disease entities from single, focal defects to advanced degenerative disease of articular (hyaline) cartilage.
    • Diagnosis generally requires an MRI to accurately assess the location of specific defects.
    • Treatment can be nonoperative or operative depending on patient age, degree of symptoms and the size of the lesion. 
  • Epidemiology
    • Incidence
      • 5-10% of people > 40 years old have high grade chondral lesions
    • Anatomic location
      • chronic ACL tear
        • anterior aspect of lateral femoral chondyle and posterolateral tibial plateau
      • osteochondritis dissecans
        • 70% of lesions found in posterolateral aspect of medial femoral condyle
  • Etiology
    • Pathophysiology
      • mechanism of injury
        • acute trauma or chronic repetitive overload
          • impaction resulting in cartilage softening; fissuring; flap tears; or delamination
        • the cause of OCD is unknown
      • pathomechanics
        • impaction forces greater than 24 MPa will disrupt normal cartilage
      • cellular biology
        • cartilage injuries have limited spontaneous healing and propensity to worsen over time
  • Anatomy
    • See Articular Cartilage Basic Science
  • Classification
      • Outerbridge Arthroscopic Grading System
      • Grade 0
      • Normal cartilage
      • Grade I
      • Softening and swelling (noted with tactile feedback with probe)
      • Grade II
      • Partial-thickness defect with surface fissures (do not reach subchondral bone or exceed 1.5 cm in diameter)
      • Grade III
      • Deep fissures at the level of subchondral bone with a diameter more than 1.5 cm
      • Grade IV
      • Exposed subchondral bone
      • ICRS (International Cartilage Repair Society) Grading System
      • Grade 0
      • Normal cartilage
      • Grade 1
      • Nearly normal (superficial lesions)
      • Grade 2
      • Abnormal (lesions extend < 50% of cartilage depth)
      • Grade 3
      • Severely abnormal (>50% of cartilage depth)
      • Grade 4
      • Severely abnormal (through the subchondral bone)
  • Presentation
    • History
      • commonly present with history of precipitating trauma
      • some defects found incidentally on MRI or arthroscopy
    • Symptoms
      • asymptomatic vs. localized knee pain
      • may complain of effusion, motion deficits, mechanical symptoms (e.g., catching, instability)
    • Physical exam
      • inspection
        • look for background factors that predispose to the formation of articular defects
          • joint laxity
          • malalignment
          • compartment overload
      • motion
        • assess range of motion, ligamentous stability, gait
  • Imaging
    • Radiographs
      • indications
        • used to rule out arthritis, bony defects, and check alignment
      • recommended views
        • standing AP, lateral, merchant views
      • optional views
        • semiflexed 45 deg PA views
          • most sensitive for early joint space narrowing
        • long-leg alignment views
          • determine the mechanical axis
    • CT scan
      • indications
        • better evaluation of bone loss
      • findings
        • used to measure TT-TG when evaluating the patello-femoral joint
    • MRI
      • indication
        • most sensitive for evaluating focal defects
      • views
        • Fat-suppressed T2, proton density, T2 fast spin-echo (FSE) offer improved sensitivity and specificity over standard sequences
        • dGEMRIC (delayed gadolinium-enhanced MRI for cartilage) and T2-mapping are evolving techniques to evaluate cartilage defects and repair
  • Studies
    • Laboratory
      • may be used to rule out inflammatory disease
  • Treatment
    • Nonoperative
      • rest, NSAIDs, physiotherapy, weight loss
        • indications
          • first line of treatment when symptoms are mild
      • viscosupplementatoin, corticosteroid injections, unloader brace
        • indications
          • controversial
          • may provide symptomatic relief but healing of defect is unlikely
    • Operative
      • debridement/chondroplasty vs. reconstruction techniques
        • indications
          • failure of nonoperative management
          • acute osteochondral fractures resulting in full-thickness loss of cartilage
        • technique
          • treatment is individualized, there is no one best technique for all defects
          • decision-making algorithm is based on several factors
            • patient factors
              • age
              • skeletal maturity
              • low vs. high demand activities
              • ability to tolerate extended rehabilitation
            • defect factors
              • size of defect
              • location
              • contained vs. uncontained
              • presence or absence of subchondral bone involvement
        • basic algorithm (may vary depending on published data)
          • femoral condyle defect
            • correct malaligment, ligament instability, meniscal deficiency
            • measure size
              • < 4 cm2 = microfracture or osteochondral autograft transfer (pallative if older/low demand)
              • > 4 cm2 = osteochondral allograft transplantation or autologous chondrocyte implantation
          • patellofemoral defect
            • address patellofemoral maltracking and malalignment
            • measure size
              • < 4 cm2 = microfracture or osteochondral autograft transfer
              • > 4 cm2 = autologous chondrocyte implantation (microfracture if older/low demand)
  • Surgical Techniques
    • Debridement / Chondroplasty
      • overview
        • goal is to debride loose flaps of cartilage
        • removal of loose chondral fragments may relieve mechanical symptoms
        • short-term benefit in 50-70% of patients
      • benefits
        • include simple arthroscopic procedure, faster rehabilitation
      • limitations
        • problem is exposed subchondral bone or layers of injured cartilage
        • unknown natural history of progression after treatment
    • Fixation of Unstable Fragments
      • overview
        • need osteochondral fragment with adequate subchondral bone
      • technique
        • debride underlying nonviable tissue
        • consider drilling subchondral bone or adding local bone graft
        • fix with absorbable or nonabsorbable screws or devices
      • benefits
        • best results for unstable osteochondritis dissecans (OCD) fragments in patients with open physis
      • limitations
        • lower healing rates in skeletally mature patients
        • nonabsorbable fixation (headless screws) should be removed at 3-6 months
    • Marrow Stimulation Techniques
      • overview
        • goal is to allow access of marrow elements into defect to stimulate the formation of reparative tissue
        • includes microfracture, abrasion chondroplasty, osteochondral drilling
      • microfracture technique
        • defect is prepared with stable vertical walls and the calcified cartilage layer is removed
          • aggressive debridement with removal of subchondral plate may lead to osseous overgrowth
        • awls are used to make multiple perforations through the subchondral bone 3 - 4 mm apart
        • relies on formation of type 1 and 2 cartilage
          • type 1 > type 2 cartilage 
        • protected weight bearing and continuous passive motion (CPM) are used while mesenchymal stem cells mature into mainly fibrocartilage
      • benefits
        • include cost-effectiveness, single-stage, arthroscopic
        • best results for acute, contained cartilage lesions less than 2 cm x 2cm
      • limitations
        • poor results for larger defects >2 cm x 2cm
        • does not address bone defects
        • requires limitation of weight bearing for 6 - 8 weeks
    • Osteochondral autograft / Mosaicplasty
      • overview
        • goal is to replace a cartilage defect in a high weight bearing area with normal autologous cartilage and bone plug(s) from a lower weight bearing area
        • chondrocytes remain viable, bone graft is incorporated into subchondral bone and overlying cartilage layer heals.
      • technique
        • a recipient socket is drilled at the site of the defect
        • a single or multiple small cylinders of normal articular cartilage with underlying bone are cored out from lesser weight bearing areas (periphery of trochlea or notch)
        • plugs are then press-fit into the defect
      • limitations
        • size constraints and donor site morbidity limit usage of this technique
        • matching the size and radius of curvature of cartilage defect is difficult
        • fixation strength of graft initially decreases with initial healing response
          • weight bearing should be delayed 3 months
      • benefits
        • include autologous tissue, cost-effectiveness, single-stage, may be performed arthroscopically
    • Osteochondral allograft transplantation
      • overview
        • goal is to replace cartilage defect with live chondrocytes in mature matrix along with underlying bone
        • fresh, refrigerated grafts are used which retain chondrocyte viability
        • may be performed as a bulk graft (fixed with screws) or shell (dowels) grafts
      • technique
        • match the size and radius of curvature of articular cartilage with donor tissue
        • a recipient socket is drilled at the site of the defect
        • an osteochondral dowel of the appropriate size is cored out of the donor
        • the dowel is press-fit into place
      • benefits
        • include ability to address larger defects, can correct significant bone loss/edema, useful in revision of other techniques
      • limitations
        • limited availability and high cost of donor tissue
        • live allograft tissue carries potential risk of infection
    • Autologous chondrocyte implantation (ACI)
      • overview
        • cell therapy with goal of forming autologous "hyaline-like" cartilage
      • technique
        • arthroscopic harvest of cartilage from a lesser weight bearing area
        • in the lab, chondrocytes are released from matrix and are expanded in culture
        • defect is prepared, and chondrocytes are then injected under a periosteal patch sewn over the defect during a second surgery
      • benefits
        • may provide better histologic tissue than marrow stimulation
        • long term results comparable to microfracture in most series
        • include regeneration of autologous tissue, can address larger defects
      • limitations
        • must have full-thickness cartilage margins around the defect
        • open surgery
        • 2-stage procedure
        • prolonged protection necessary to allow for maturation
    • Patellar cartilage unloading procedures
      • Maquet (tibia tubercle anteriorization)
        • indicated only for distal pole lesions
        • only elevate 1 cm or else risk of skin necrosis
        • contraindications
          • superior patellar arthrosis (scope before you perform the surgery)
      • Fulkerson alignment surgery (tibia tubercle anteriorization and medialization post
        • indications (controversial)
          • lateral and distal pole lesions
          • increased Q angle
          • offloading patellofemoral joint cartilage restoration procedures
        • contraindications
          • superior medial patellar arthrosis (scope before you perform the surgery)
          • skeletal immaturity
    • Matrix-associated autologous chondrocyte implantation
      • overview
        • example is "MACI"
        • cells are cultured and embedded in a matrix or scaffold
        • matrix is secured with fibrin glue or sutures
        • results in Type I and Type II collagen
      • benefits
        • only FDA approved cell therapy for cartilage in the USA
        • include ability to perform without suturing, may be performed arthroscopically
      • limitations
        • 2-stage procedure
        • Expense
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