Updated: 5/31/2021

Articular Cartilage Defects of Knee

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  • 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
        • 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, 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
        • 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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Questions (14)
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(SBQ16SM.18) A 30-year-old active-duty woman presents to your clinic with right knee pain and without any history of trauma. She is an avid runner and is part of the Army 10-miler team. Her pain is located directly over her medial femoral condyle (MFC). Additionally, she describes intermittent episodes of an inability to fully extend her knee. Her clinical mechanical alignment, patellar tracking, meniscal examination, and ligamentous examination are all equivocal on physical examination. Your diagnostic imaging workup with pertinent findings is represented in Figures A through E. You perform a diagnostic arthroscopy to confirm that the pathology is isolated to the medial compartment and you note that there is not any evidence of ligamentous or meniscal pathology. Based on your findings which definitive surgical options would you recommend to the patient?

QID: 211304
FIGURES:
1

Proximal tibia valgus osteotomy, microfracture to the MFC, and removal of loose osteochondral bodies

7%

(118/1620)

2

Distal femur varus osteotomy and autologous chondrocyte implantation to the MFC

1%

(23/1620)

3

Osteochondral autograft transplantation to the MFC

19%

(302/1620)

4

Removal of loose osteochondral bodies and osteochondral allograft transplantation to the MFC

68%

(1107/1620)

5

Patellofemoral realignment osteotomy, removal of loose osteochondral bodies, and autologous chondrocyte implantation to the MFC

3%

(52/1620)

L 3 B

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(SBQ16SM.7) Figures A-C are the arthroscopic, radiographic and MRI images of a 34-year-old male who has had knee pain for the past 11 months. He has failed conservative and arthroscopic management under the care of another physician. He comes to you for a second opinion. The decision is made to proceed with osteochondral allograft transplantation to the medial femoral condyle. All of the following are contraindications for this surgery except:

QID: 211183
FIGURES:
1

Osteochondral defect measuring > 2 cm2

77%

(1331/1736)

2

Uncorrectable limb malalignment

4%

(64/1736)

3

Ligamentous instability of the knee

4%

(77/1736)

4

Meniscal insufficiency

10%

(168/1736)

5

Multi-compartmental arthrosis

5%

(87/1736)

L 2 B

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(OBQ13.99) A 35-year-old man presents with mechanical knee pain after a fall. An arthroscopic picture taken during diagnostic arthroscopy is shown in Figure A. His surgeon considers treatment with Technique B and Technique C, which are shown in Figures B and C, respectively. Which of the following statement is true with respect to Technique B and C?

QID: 4734
FIGURES:
1

A diminished immune response to transplanted chondrocytes is seen in Technique C because the dense cartilage matrix acts as a barrier that limits antigen exposure.

5%

(334/6535)

2

In Technique C, healing is initiated by mesenchymal stem cell migration from subchondral bone. In Technique B, healing is initiated by allogeneic chondrocytes reimplanted beneath a periosteal patch.

4%

(234/6535)

3

Grafts in Technique C are transferred to an antibiotic solution to kill microorganisms and stored at 4°C until use.

7%

(477/6535)

4

A biopsy of the repair site at 3 months will reveal more Type I collagen in Technique B than in Technique C.

72%

(4706/6535)

5

Technique C is a 2-stage procedure. Technique B is a single-stage procedure.

11%

(709/6535)

L 3 C

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(OBQ13.152) A 25-year-old patient undergoes the procedure seen in Figure A. Which of the following statements best describes the incorporation of the graft and biopsy results of the graft at one year?

QID: 4787
FIGURES:
1

The transplanted chondrocytes are viable and articular cartilage heals. Biopsy shows type I collagen.

12%

(677/5679)

2

The transplanted chondrocytes are viable and articular cartilage heals. Biopsy shows type II collagen.

59%

(3332/5679)

3

The transplanted chondrocytes are nonviable and cartilage is used as a scaffold for growth of new articular cartilage. Biopsy shows type II collagen.

6%

(367/5679)

4

The transplanted chondrocytes are nonviable and articular cartilage is gradually replaced by fibrocartilage. Biopsy shows type I collagen.

9%

(489/5679)

5

The transplanted chondrocytes are nonviable and articular cartilage is gradually replaced by fibrocartilage. Biopsy shows mixture of type I and II collagen.

13%

(744/5679)

L 4 B

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(OBQ13.203) What type of tissue is formed by the activation of marrow mesenchymal cells following subchondral drilling of an 8x7 mm osteochondral defect?

QID: 4838
1

Elastic cartilage

0%

(11/5714)

2

Fibrocartilage

96%

(5476/5714)

3

Hyaline cartilage

1%

(84/5714)

4

Trabecular bone

1%

(49/5714)

5

Hypertrophic chondrocytes

1%

(68/5714)

L 1 B

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(OBQ11.1) A 24-year-old female has moderate arthrosis of the medial facet of the patella and the medial femoral condyle. Which of the following procedures is contraindicated?

QID: 3424
1

Anterior (Maquet) tibial tubercle osteotomy

4%

(196/4820)

2

Anteromedial (Fulkerson) tibial tubercle osteotomy

74%

(3587/4820)

3

Anterolateral tibial tubercle osteotomy

10%

(475/4820)

4

Medial opening wedge high tibial osteotomy

7%

(320/4820)

5

Lateral closing wedge high tibial osteotomy

4%

(204/4820)

L 2 C

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(OBQ10.257) Following a medial femoral condyle osteochondral autograft mosaicplasty, which of the following statements best describes the fixation of the graft?

QID: 3353
1

Graft fixation strength increases linearly with time until subchondral union at 3 months

6%

(127/2019)

2

Graft fixation strength initially decreases during the early healing phase, and then increases with subchondral bone healing

84%

(1706/2019)

3

Graft fixation strength does not change during the first 3 months following surgery

2%

(33/2019)

4

Graft fixation strength is enhanced by early weight bearing

3%

(62/2019)

5

Graft fixation strength initially increases over the first 6 weeks, then recedes with bony remodeling

4%

(82/2019)

L 2 C

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(OBQ08.94) A 32-year-old female is referred to you for definitive treatment of a symptomatic focal chondral defect on her medial femoral condyle. A photograph from a recent diagnostic arthroscopy shows the defect (Figure A), which measured 25 x 25mm after debridement. What surgical treatment would you recommend?

QID: 480
FIGURES:
1

Osteochondral autograft with 1-2 plugs

25%

(313/1256)

2

Osteochondral allograft

60%

(749/1256)

3

Microfracture

13%

(161/1256)

4

Unicompartment arthoplasty

1%

(16/1256)

5

Abrasion arthroplasty

0%

(5/1256)

L 4 D

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(SBQ07SM.32) A patient with a symptomatic chondral defect undergoes the arthroscopic procedure seen in Figure A. The reparative tissue would best be described as which of the following?

QID: 1417
FIGURES:
1

Fibrocartilage

92%

(1455/1577)

2

Fibrous tissue

3%

(42/1577)

3

Elastofibroma

0%

(5/1577)

4

Hyaline cartilage

3%

(50/1577)

5

Chondromalacia

1%

(13/1577)

L 1 C

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(OBQ06.186) All of the following are acceptable scenarios for the use of autologous chondrocyte implantation (ACI) in the patellofemoral joint EXCEPT:

QID: 372
1

Grade 4 lesion of the medial femoral condyle

10%

(277/2759)

2

Grade 4 lesion of the trochlea

6%

(156/2759)

3

Joint space narrowing on Merchant view

56%

(1556/2759)

4

Varus mechanical axis on standing full length radiograph

23%

(639/2759)

5

Concomitant anteromedial tibial tubercle transfer osteotomy (Fulkerson's)

4%

(120/2759)

L 4 D

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