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What is Arthrofibrosis

Arthrofibrosis means fibrosis of a joint. Fibrosis is the excessive production of scar tissue and inflammation by specialised wound healing cells called myofibroblasts. The scar tissue inside the joint adheres to surrounding tissues and contracts, and this frequently reduces the range of motion (ROM) of the joint. While not everybody with arthrofibrosis has a significant reduction in ROM, they can be significantly impacted by pain, particularly during and after activity. 
The location and extent of fibrosis varies between individuals - all the soft tissues in a joint can be affected, including the joint capsule, fat pads, nerves, tendons and muscles, however, fibrosis can be localised to only one area. As a consequence symptoms and response to treatment vary.

The joint feels stiff

The joint feels stiff, typically has restricted range of motion and is painful in the active phase. Sometimes the cause can’t be identified and this is often the case for shoulder arthrofibrosis, where micro-tears may be responsible. Shoulders are the most common joint affected [1].

Arthrofibrosis can affect any joint and is referred to by a number of names including frozen shoulder, adhesive capsulitis, joint contracture, frozen hip, frozen ankle and stiff elbow.

Estimates of the rates of knee arthrofibrosis following anterior cruciate ligament reconstruction range from 2% to 35%, and after total-knee reconstruction between 2% and 10% with others reporting rates up to 15%. The dysregulated healing response and chronic inflammation that cause arthrofibrosis are complex biochemical processes, and biochemical solutions (medications, supplements and other treatments) are an essential part of treatment [1,2].

(Image: a healthy knee. From Usher et. al. 2019)

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Inflammation is a key player in arthrofibrosis

Inflammation is a key player in arthrofibrosis [1]. Only after inflammation is properly controlled can the body end the fibrosis process. Therefore, reducing inflammation should be a top priority.

Aggressive physical therapy programs are not appropriate for treating arthrofibrosis, because exercise and aggressive stretching cause inflammation and damage [2]. Evidence suggests that this is a dangerous approach and a joint should be exercised in the pain-free zone. 

Evidence from organ fibrosis suggests that there are two forms, an active form in which inflammation and pain are present, and a residual form in which inflammation and pain have resolved, but stiffness remains [1]. In shoulder arthrofibrosis the residual phase is known as the “frozen phase”. The stiffness of residual arthrofibrosis may resolve over time as the body breaks the collagen bonds in the scar tissue.

However, if inflammation persists arthrofibrosis can’t resolve. The common myth that arthrofibrosis of shoulders and other joints always resolves is not scientifically valid, and the condition can become permanent [1]. The same is true for all forms of fibrosis, wherever they occur. Early and appropriate treatment is essential.

(Image: a knee with generalised arthrofibrosis. Major areas that are affected by arthrofibrosis are indicated. From Usher et. al. 2019)

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Aspects of Arthrofibrosis

Cells and Cytokines

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Myofibroblasts

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Hoffa’s Fat Pad

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Pathogenesis

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Predisposition

DNA Strand

Drivers

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References

  1. de la Serna, D., Navarro-Ledesma, S., Alayón, F., López, E. & Pruimboom, L. A Comprehensive View of Frozen Shoulder: A Mystery Syndrome. Frontiers in Medicine8, doi:10.3389/fmed.2021.663703 (2021).

  2. Usher, K. M., S. Zhu, G. Mavropalias, J.A. Carrino, J. Zhao, and J. Xu (2019) Pathological mechanisms and therapeutic outlooks for arthrofibrosis. Bone Research 7:9

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