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Cartilage Injuries in the Knee

Causes of Patellofemoral Cartilage Injury

  • Patellar Instability ("loose kneecap")

    • Often the caused by underlying anatomical risk factors such as a shallow groove (trochlear dysplasia), increased Q-angle ("knock-kneed"), a high-riding kneecap (patella alta), or an unbalance of the ligaments holding the kneecap in place

  • Cartilage becomes damaged in up to 96% of patellar dislocations

  • Chronic maltracking

  • Direct trauma

    • Direct fall onto the knee​

    • Knee hitting dashboard in car accident

  • Repetitive microtrauma

    • Repeated jumping (volleyball, basketball)​

    • Prolonged knee flexion (baseball catcher)


Magnetic Resonance Imaging (MRI)

  • Better for visualizing cartilage, but not perfect

  • Requires cartilage-specific sequences, including standard spin-echo (SE) and gradient-recalled echo (GRE), fast SE, and, for cartilage morphology, T2-weighted fat suppression (FS) and 3-dimensional SE and GRE.

Radiographs (X-Ray)

  • X-rays do not show cartilage directly.  However, they can be helpful to see ​if the bones are in the correct alignment and to check if the patella (kneecap) is centered in the groove

Non-Operative Treatment


  • First-line treatment when symptoms are mild

"Core to Floor" Rehabilitation

  • Focuses on weight loss and achieving adequate range of motion of the spine, hips, and knees along with muscle strength and flexibility of the core and lower limbs

  • The full process can take 6-9 months, but there should be some improvement by 3 months

Injection Therapy

  • Corticosteroid, hyaluronic acid, or platelet-rich plasma (PRP) injections can provide temporary relief and facilitate rehabilitation

NSAIDs (Non-Steroidal Anti-Inflammatory Drugs)

  • Iburofen

  • Meloxicam

  • Diclofenac

Unloader Brace

  • A special brace that takes pressure off of the injured cartilage area in the knee

Operative Treatment


  • Surgery is indicated for full-thickness or nearly full-thickness areas that is > 1x1 cm after failed conservative treatment


  • Clinical outcomes have been poor (reference)

  • Deterioration becomes significant after about 36 months

  • Should be restricted to low-demand patients with small (< 1x2cm) well-contained lesions in the groove

Autologous Chondrocyte Implantation (ACI)

  • This is a two-step procedure that uses your own cartilage cells to treat a cartilage injury

  • The first step is a 30 minute arthroscopic procedure in which a small piece of articular cartilage is taken from a part of the knee and sent to a laboratory and grown for a period of 6-8 weeks

  • The second procedure is an open procedure in which the cells are placed back into the defect in the knee and covered with a biologic patch to form what is known as hyaline-like cartilage resembling native joint cartilage

  • Following implantation of the cartilage cells, there is a period of restricted weight-bearing for up to 8 weeks 

  • Return to light sports activities is typically allowed at approximately 6 months with return to full sports activities between 9 and 12 months following the procedure

  • The overall success rate of ACI is approximately 85% in allowing patients to return to pain-free activities.

  • Multiple case series with midterm and longterm follow-up have found improved outcomes for patella and trochlea (reference 1, reference 2)

Osteochondral Autograft Trasfer (OAT)

  • This procedure uses cartilage from a healthy part of your knee to replace the cartilage that is missing from the damaged part

  • This option is limited though with cartilage injuries of the patellofemoral joint because the healthy cartilage is usually harvested from the patellofemoral joint

  • This can be a good option in selected patients with small lesions that are limited to one side of the patella (not including the ridge or groove) that require one plug (reference)

Osteochondral Allograft (OCA)

  • This procedure replaces damaged cartilage with healthy cartilage that is obtained from a donor (donated human tissue)

  • A circular plug of cartilage and bone is removed from the donor knee and placed in the patients knee where the cartilage is missing

Emerging Technologies


  • Dehydrated, micronized allogeneic cartilage scaffold implanted with platelet-rich plasma and fibrin glue

  • For small, contained lesions

  • Limited clinical studies of short or long-term outcomes

Fresh and Viable Osteochondral Allograft

  • Fresh OCA (ProChondrix; AlloSource)

  • Viable cryopreserved OCA (Cartiform; Arthrex)

  • This osteochondral scaffolds that contain viable chondrocytes and growth factors

  • Indicated for lesions from 1x1 to 1x3 cm

  • No clinical studies on outcomes

Bone Marrow Aspirate Concentrate Implantation

  • Mesenchymal stem cells harvested from the iliac crest are implanted under a synthetic scaffold

  • Indications are the same as that for ACI

  • Medium-term follow-up studies in the PF joint have shown good results similar to those obtained with matrix-induced ACI (reference)

Particulated Juvenile Allograft Cartilage

  • Minced cartilage allograft (from juvenile donors) is cut into cubes ( about 1 mm) can be used to fill lesions from 1-6 cm

  • Short term outcomes have been good (reference)

Comments & Questions

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