Knee surgery

Dr Cox has subspecialty fellowship training in all areas of knee surgery including:

  • arthroscopic ligament reconstruction and meniscal surgery
  • repair of acute knee injuries
  • patellofemoral realignment and stabilisation
  • realignment osteotomy and chondroplasty
  • joint replacement (unicompartmental, total and complex revision)


Arthroscopy is a common technique used to examine and treat problems inside the knee joint. A fibre-optic telescope, about the size of a pencil, is inserted into the knee through a small incision, allowing the surgeon to visualise structures inside the joint. A second incision is then made to pass very thin surgical instruments into the knee in order to treat the problem. The term ‘arthroscopy’ refers to an approach to the knee rather than the operation itself. The advantages of this form of keyhole surgery include faster healing and lower complication rates than previous open procedures.

arthroscopy - patient info

Ligament reconstruction

The most commonly injured knee ligament requiring surgery is the anterior cruciate ligament (ACL).  If torn, the ACL itself has very limited capacity for repair, but with activity limitation, the knee can still function adequately.  ACL reconstruction is indicated in patients who wish to return to cutting or impact sports, or when the knee continues to give way (instability symptoms). The ACL is reconstructed using your hamstring tendons (or part of your patella tendon) to recreate the ACL’s proprioceptive and protective function.

Other knee ligaments include the posterior cruciate ligament (PCL), medial collateral ligament (MCL) and posterolateral corner (PLC) complex made up of the lateral collateral ligament (LCL) and popliteus tendon.  Finally, the quadriceps tendon (thigh muscle into knee cap) and patella tendon (knee cap into shin bone) complete the extensor mechanism attachments around the knee.

Each of the tendons and ligaments can require repair or reconstruction depending on the type and chronicity of the injury.  Acute repair or reconstructions with autograft (your own tendons, usually hamstrings) or synthetic grafts (LARS ligaments) each have relative advantages which need to be considered for each patient and injury.

knee reconstruction - patient info

Meniscal surgery

There are two menisci in each knee (medial and lateral).  They are made of a special type of fibrocartilage and have two primary functions.  They increase the contact area between the femur and tibia, especially the lateral meniscus, acting as a shock absorber during daily activities.  They also help improve the stability, especially the medial meniscus, complementing the ACL ligament.

Meniscal tears in younger people (<40yo) are often the result of acute trauma in an otherwise normal meniscus. Early repair, if successful, allows the meniscus to return to its normal functions.  In older people, or chronic tears, the meniscus is usually sufficiently damaged that repair is less likely to be successful.  In these cases, excision of the torn fragments can improve mechanical and synovitis symptoms from the tear or associated meniscal cysts.  If the knee already has significant arthritis symptoms, then meniscal surgery is rarely indicated.

Meniscal repair rehab protocol

Acute knee injuries

Acute knee injuries range from minor sprains and swelling (effusions) to complete knee dislocations which can compromise the nerve and blood supply to the entire leg.  As such, a detailed history of the injury and preinjury function, along with a focused clinical examination and investigations (Xray and/or MRI) is required before the diagnosis can be made and specific management recommended.  In some cases, a specific brace and/or physiotherapy program may yield good functional outcomes, whilst others may require early surgical repair or reconstruction.

knee reconstruction - patient info

Patellofemoral realignment and stabilisation

The patella (knee cap) is a bone within the quadriceps tendon that glides in a groove on the femur (trochlea).  First time dislocations are usually the result of a specific contact injury, in which the medial patellofemoral ligament (MPFL) is torn.   Acute surgery is rarely indicated for this injury in isolation but is recommended if associated with a significant osteochondral fracture, loose body or combined injury.  Rehabilitation involves dedicated strengthening (VMO and Gluteus medius) and proprioceptive retraining.

Recurrent instability is uncommon after adequate rehabilitation unless specific biomechanical parameters are present.  These include patients with trochlea dysplasia (shallow groove), patella alta (high patella), lateralised tibial tubercle (increase Quadriceps “Q” angle) and ligamentous laxity (“double jointed” or high flexibility”).  In these cases, persistent instability can be very debilitating, so patellofemoral stabilisation including realignment surgery to correct the above parameters (often tibial tubercle transfer), combined with MPFL reconstruction (using a hamstring tendon) is indicated.

Realignment osteotomy, microfracture and chondroplasty

Knee alignment has a profound effect on the forces going through each compartment of the knee.  Varus alignment (bow legs) increases the forces on the medial (inside) half of the knee and valgus alignment (knock knees) increases the forces of the lateral (outside) half of the knee.  With progressive arthritis is an isolated compartment, the malalignment worsens, which further exacerbates the arthritic symptoms.

In younger (<60yo), active individuals with isolated arthritis and associated malalignment (usually medial arthritis and bow leg), correction (or slight overcorrection) of the alignment can unload the arthritic compartment and take the weight through the non-arthritic part of the knee.  This aims to provide symptomatic relief whilst preserving the native knee and delaying the need for knee replacement in the medium future.

The osteotomy (cut bone) is usually done in the proximal tibia (shin bone), so is known as a high tibial osteotomy (HTO).  It involves partially cutting the bone under controlled conditions, correcting the alignment and then fixing the newly created “fracture” with a plate and screws until the osteotomy heals.

Osteotomy is usually combined with simultaneous arthroscopy to assess the wear and tear in the remainder of the knee and treat any associated mechanical symptoms that arise from meniscal tears or loose bodies.  Localised cartilage damage can be managed with microfracture (drilling the base of the cartilage defect to stimulate the underlying bone marrow healing response) or chondroplasty (trimming and sealing the edges of localised cartilage damage to attempt to prevent propagation of loose cartilage flaps).

Knee replacement (arthroplasty)

Osteoarthritis is the destructive process in which joint cartilage wears out, leaving the bones rubbing directly on each other.  This is associated with variable degrees of pain and stiffness. Joint replacement (arthroplasty) surgery involves cutting away worn out bone and cartilage and replacing those articulating surfaces with a combination of metallic knee implants and highly specialised plastic (polyethylene).

The primary indication for knee replacement surgery is painful advanced arthritis.  It is a common procedure with most patients reporting improved pain and function after their recovery.  However, each patient must weigh these potential benefits against the risks (which include infection, stiffness, implant loosening, persistent pain and medical complications).

Total knee replacement (TKR)

The knee joint is functionally separated into 3 compartments.  The medial (inner) compartment is the most commonly affected, followed by the patellofemoral (knee cap) and lateral (outer) compartments.  Total knee replacement involves replacing all of the above compartments and is indicated when the arthritis and pain are generalised throughout all compartments.  Dr Cox uses a combination of computer navigation and patient specific implant jigs to ensure the accuracy of alignment of the knee replacement implants.  It is hypothesised that this will improve the functional outcomes and implant longevity of modern knee replacement implants.

Total Knee Replacement (TKR) - patient info

Unicompartmental knee replacement (UKR)

In some cases, the arthritis and pain are localised to only one compartment (most commonly medial) and so only that compartment needs to be replaced.  This is called Unicompartmental (“uni” or “partial”) knee replacement.  In properly selected patients this procedure is functionally superior to total knee replacement, has an easier recovery and a lower risk of major complications.  However, it has the risk of requiring revision surgery to a total knee replacement and many patients are not suitable for specific reasons.

Revision total knee replacement

Whilst knee replacements are very successful, they do not last forever.  Unlike the normal knee, the mechanical components of a knee replacement have no capacity for repair, and so will wear out over time.  Unfortunately, the wear particles generated stimulate an inflammatory reaction in the body, which leads to loosening of the implants in the bone.  This is known as aseptic loosening and is associated with pain which often requires revision.  Other causes for revision include infection (either soon after or years after the original surgery), stiffness, instability and injury.

Revision surgery is more complex than primary knee replacement.  Issues to consider include previous scars, bone loss, stretched ligaments, deformity and the removal of failing implants.  It has a higher complication rate than primary surgery and so only significant pain and dysfunction justify the risks. Despite these risks, a good outcome can be expected in most cases as long as a careful approach is taken to preoperative workup and surgical technique.

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