Part 1 - Introduction to arthrofibrosis

What is arthrofibrosis?

Arthrofibrosis is a complication of knee injury or surgery where an excessive scar tissue response leads to painful restriction of knee flexion, extension, or both.

The scar tissue may form intra-articularly (within the joint) and extra-articularly (outside the joint, in soft tissue spaces) and persists despite routine rehabilitation and knee motion exercises.

The consequent pain and restricted knee motion may lead to a cascade of events which include quadriceps atrophy and weakness, patellar tendon adaptive shortening, and scarring in the tissues around the patella - with an end result of permanent patella infera - where the patella is pulled down into an abnormal position and becomes likely to incur damage to the articular cartilage. In severe cases of arthrofibrosis, the disorder becomes progressive and the whole capsule may become thickened and tight with almost no movement possible in the joint.

Despite this potentially disastrous cascade of events, patients with developing arthrofibrosis and early patella infera may avoid the necessity for surgical intervention by participating in a closely supervised therapy programme. In other cases, surgical excision of the excessive scar tissues followed by a specific in-patient physical therapy program can be successful in regaining significant motion. The key is early recognition and referral to a unit experienced in dealing with arthrofibrosis.

In this course I will try and help delegates understand the precipitating causes, the danger signals, and the early and late management of this potentially disastrous disorder.

adhesions0825 — Section through the knee joint, showing four common sites of scarring in the knee - above and below the patella (kneecap) and at the back of the joint cavity.

In arthrofibrosis the range of motion loss is due to disordered healing -

adhesions stretching across the joint spaces maturing into fibrous tissue
this fibrous tissue slowly contracting to pull these spaces closed
the fibrous tissue thickening the joint capsule and slowly contracting to tighten it up.

The loss of range of motion is secondary to this fibrous over-response. As we progress through this course, I will explain to you the set of symptoms and signs which make one suspicious that the cause of a limited ROM is indeed arthrofibrosis and not something else.

Defining Arthrofibrosis

When discussing arthrofibrosis, it is useful to refer to the grading system established by Dr Donald Shelbourne. He categorised arthrofibrosis into four types (ref 1):

Type 1 - < 10 degree extension loss and normal flexion
Type 2 - > 10 degree extension loss and normal flexion
Type 3 - > 10 degree extension loss and > 25 degree flexion loss with a tight patella
Type 4 - > 10 degree extension loss, 30 degrees or more flexion loss, and patella infera with marked patellar tightness

Thus failure to re-establish full range of motion (ROM) after a routine programme of rehabilitation is a key indicator of arthrofibrosis. One must remember, however, that loss of ROM of motion on its own does not mean that arthrofibrosis is necessarily the cause. There may be a different mechanical problem preventing full movement within the knee, for example an unrecognised bucket-handle tear of the meniscus or anterior cruciate ligament graft placed in an improper position in the joint.

What makes the knee vulnerable to arthrofibrosis?

Certain conditions tend to make the knee vulnerable to arthrofibrosis -

the original injury itself - for example a fracture near the joint, injury complicated by haemarthrosis, multiple ligament injury (especially if both ACL and PCL are torn), dislocation of the knee, infection, inflammation (synovitis), associated meniscal tears, disruption of the extensor mechanism (tibial tubercle avulsion, quadriceps rupture, patellar tendon rupture, patellar fracture).
the treatment - for example arthroplasty, anterior cruciate ligament graft too tight or poorly positioned, poor timing of graft procedure, high tibial osteotomy, prolonged immobilisation in a cast
post-op complications - for example post-op haemarthrosis (eg after lateral release), inflammation, synovitis, infection, RSD
the rehabilitation - for example prolonged immobilisation, poor rehabilitation programme, poor adherence to rehabilitation

Arthrofibrosis triggered by such conditions is referred to as secondary arthrofibrosis, as the scarring is a local phenomenon and not part of a generalised healing disorder. However, arthrofibrosis can also be triggered without these predisposing conditions in patients who have a general problem with scar tissue biology, and who tend normally to produce excessive scar tissue in response to any injury or surgery anywhere in the body. In these cases, the arthrofibrosis is termed primary arthrofibrosis. The cause of primary arthrofibrosis is not yet known, but the current assumption is that it is genetically-determined. Investigators are currently studying patients with primary arthrofibrosis to determine if they can identify the guilty gene or genes (eg ref 2). Of course, a person with the primary predisposition may be unfortunate enough to suffer also from one of the high risk conditions.

How common is arthrofibrosis?

The incidence of arthrofibrosis is fortunately decreasing as clinicians become better at understanding and preventing the full-blown disorder.

A survey of the medical literature published over the last twenty years provides us with some idea of the current size of the problem, in at least some of the conditions I have mentioned.

A review of the literature suggests that stiffness after total knee replacement occurs in about 1% of cases (ref 3).

Arthrofibrosis is the most common complication of ACL reconstruction (ref 4). In the 1980's, ACL reconstruction was associated with incidences of arthrofibrosis of approximately 19%, and in some studies was reported to be as high as 35% (ref 5). The loss of motion from the arthrofibrosis was often more disabling than the original instability for which the surgery had been performed. Currently, with improved understanding and changes in surgical timing and technique and rehabilitation, the incidence for this procedure is less than 10%. In our Center, a focus on immediate knee motion and early management of extension and flexion limitations after ACL reconstruction has shown our rate to be less than 1% in major studies conducted on over 600 patients (refs 6-8).

Many early publications reported an unacceptably high incidence of arthrofibrosis after high tibial osteotomy. Windsor and colleagues, for example, in 1988 reported that 80% of their patients developed patella infera following closing wedge high tibial osteotomy with cast immobilisation. Some ten years later Westrich and colleagues were able to show greatly reduced incidences when patients were mobilised early, without a prolonged period in a cast. In our experience, immediate knee motion begun the day following either closing or opening wedge osteotomy has resulted in a 0% incidence of arthrofibrosis (refs 9-11).

It is not easy to determine the incidence of arthrofibrosis triggered purely by immobilisation, as a plaster cast is usually applied in association with another problem, which may in itself be a trigger, eg patellar fracture. Suffice it to say that the trend in knee surgery is to minimise immobilisation to avoid arthrofibrosis.

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