Patellar Clunk Syndrome: Complication Following Knee Replacement Surgery

In general, (TKR) is a highly successful procedure. However, complications, although relatively rare, can sometimes occur. One such complication is known as .

To understand this condition, it helps to first understand a little bit about knee anatomy and function (Figure 1). During knee flexion and extension, the patella (knee-cap) rides within a groove in the femur (thigh bone).

Knee Anatomy

Figure 1: Basic Knee Anatomy

In knee replacement the worn ends of the bones are “resurfaced” with metal and plastic implants. The patellar groove is part of the metal femoral component that is implanted onto the prepared femur during the total knee replacement procedure. At the end of this groove there is a transition between the metallic implant and the native bony surface.

Following knee replacement, scar tissue can sometimes form at the top or “superior pole” of the patella. During particularly deep flexion, this scar tissue may move below the end of the groove in the femoral component and then “catch” on the end of the groove as the patella moves back with knee extension. It is this catching and then forceful release with extension that results in the “clunk” and pain characteristic of this condition.

This condition is more prevalent in a type of knee replacement known as Posterior Stabilized, or “PS” knee replacement, although it has also been reported in Cruciate Retaining (CR) knee designs as well. 1 In PS knee designs, where the posterior cruciate ligament is removed, the patellar groove tends to be shorter to avoid contact (in extension) between the end of the groove and a plastic post on the tibial component found in these types of designs. Consequently, the patella can come off the end of the groove during lesser degrees of flexion.

The publication cited at the end of this article provides more detailed information and a review of some of the literature on patellar clunk.

1 Niikura T, Tsumura N, Tsujimoto K, Yoshiya S, Jurosaka M, Shiba R. Patellar Clunk Syndrome After TKA with Cruciate Retaining Design: A Report of Two Cases. Orthopedics. 2008: 31:90

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Joint Stiffness: Complications Following Knee Replacement Surgery

In a relatively recent article 1 published in the Musculoskeletal Journal of Hospital for Special Surgery, Dr. Alejandro Gonzalez Della Valle et al reviewed the origins of and treatments for early onset stiffness,  a common complication following knee replacement surgery. We’ll present a brief summary of the article here.

How Prevalent is Stiffness after Knee Replacement?

In a review of the literature, the authors state that stiffness occurs in roughly 6% of cases, making it the most common knee replacement surgery complication.

How is Stiffness Defined?

The researchers reveal that what is perceived as “stiffness” following knee replacement has evolved over time. Several years ago, a knee was considered stiff if the patient could not extend their knee beyond 25 degrees of flexion (that is, a flexion contracture of 25 degrees) or if the full arc of motion was less than 45 degrees. More recently, as surgical technique and implant design have improved and as younger, more active patients receive implants, expectations have changed. Today, stiffness has been defined as a equal to or greater than only 10 degrees or an arc of motion less than 95 degrees. The authors note that this degree of motion is what is required for common activities of daily living (walking, sitting, stair climbing). Practically speaking, a joint can be considered “stiff” when it limits the patient’s ability to perform such activities.

What Causes Stiffness after Knee Replacement?

The authors place the causes of stiffness into three broad categories:

Preoperative – These include things like post-traumatic osteoarthritis, patients with prior high tibial osteotomy and patient whose preoperative range of motion (ROM) is limited.

Intraoperative – Included here are what the authors termed “technical errors” during the procedure. Things like, improperly sized implants and poor “balancing” of the joint through improper bone preparation fall into this category. The researchers explain these as well as other technical errors in detail.

Postoperative - Following surgery, stiffness can be caused by additional factors. Some examples are by patient behavior (“poor patient motivation”) deep infection and inadequate pain management.

How is Stiffness Treated

The authors then outline the various ways in which stiffness can be treated following knee replacement. Manipulation of the knee by the surgeon under anesthesia is generally successful when used within the first three months after surgery. After this period, more aggressive surgical options should be considered since manipulation can result in fracture or soft-tissue damage. Some surgical treatments described are arthroscopy, tibial insert (or spacer) exchange and revision surgery (i.e. exchange of the femoral component typically to correct imbalance in the spacing between the thigh and shin bone created at the time of surgery). The authors also stress the importance of proper rehabilitation following knee replacement.

The original article is available online through PubMed Central.

1. Gonzalez Della Valle A, Leali A, Hass S: Etiology and Surgical Interventions for Stiff Total Knee Replacements. HSSJ 2007, 3: 182-189

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What do Cherries and Seaweed Have in Common? They Both May Help Your Osteoarthritis

Osteoarthritis (OA) is joint inflammation caused by the breakdown and eventual loss of articular cartilage. It is characterized by pain, stiffness, and swelling. Recent reports suggest that two natural substances could help reduce pain and improve function in patients suffering from this often debilitating disease.

Researchers at the Baylor Research Institute 1 conducted a pilot study where patients took pills made from tart cherries. This particular group of patients suffered from osteoarthritis of the knees. The scientists found that more than half of the patients had significant improvement in pain and function after taking the pills for eight weeks. These encouraging preliminary results have prompted the researchers to embark on a broader study. It will be interesting to see if the favorable results continue.

In a separate study 2, the use of a supplement made from seaweed was examined. In this study, patients were given a pill derived from a seaweed rich in calcium, magnesium and other minerals. The authors noted that earlier studies have shown that mineral supplements may improve OA symptoms. In this particular study, patients who received the pill were able to walk farther in a controlled test and experienced a small improvement in range of motion when compared to a group receiving a placebo. The study is available online through PubMed Central.

1 “Can Cherries Relieve the Pain of Osteoarthritis.” www.baylorhealth.com 31 Mar. 2009. http://www.baylorhealth.com/About/NewsRoom/BaylorNews/Pages/03182009Cherries.aspx

2 Frestedt JL, Kuskowski MA, Zenk JL. “A Natural Seaweed Derived Mineral Supplement (Aquamin F) for Knee Osteoarthritis: A Randomised, Placebo Controlled Pilot Study” Nutrition Journal, 8:7, 2009

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