Recurrent, chronic hip dislocations and subluxations

Ross Hauser, MD.

This is a sub-article to the companion articles:

Due to the widespread accessibility to chiropractic and osteopathic care, as well as the Internet, people are beginning to understand the signs and symptoms of hip instability and subluxations. Those who have catching or a ‘giving way’ sensation in the hip or cannot hold chiropractic or osteopathic adjustment likely have some degree of hip instability. Additionally, anyone with a history of even one hip dislocation with resultant hip pain more than likely has developed hip instability.

The most common type of hip dislocation is a posterior (rear) dislocation caused by a posteriorly directed force transmitted through a bent knee, such as landing on a bent knee or being tackled with the hip and knee flexed. Motor vehicle accidents are also a common cause in which the hip and knee are flexed and the knee comes in contact with the dashboard, placing rearward force on the hip. In cases of lesser severity that do not involve a fracture, hip dislocations naturally injure or damage much of the capsuloligamentous complex and it can be assumed that the labrum is also damaged in this process. A serious complication of hip dislocation is avascular necrosis. Another complication may include recurrent subluxations (also called partial dislocations) of the hip joint due to the stretched-out ligaments and capsule.

Post-traumatic hip microinstability can occur after the presence of a hip dislocation due to injury to the hip capsule, surrounding ligaments, and possible labral tears. Personally, I think all people that suffer a hip dislocation that did not require surgery should be assessed for micro or subclinical (not detectable on MRI) hip ligament problems.

When there is even a minor osteomisalignment, called a subluxation, repetitive forces on the hip joint can stress and damage the soft tissues, resulting in microinstability. Repetitive joint forces stress the anterior soft tissues, including the anterior labrum and capsuloligamentous complex, as the femoral head glides forward. If the anterior joint translation (the movement of the hip forward) continues to increase, eventually the joint won’t be able to tolerate the load, causing the labrum to tear and the capsular ligament to stretch. (1)

Due to the naturally slow and often incomplete healing of ligaments, it is likely that in many instances that the numerous soft tissues in the hip were damaged from the dislocation (not limited to the three main ligaments, but also including tendons and other structures). Prolotherapy works to strengthen these injured tissues to help recreate stability in the joint and reduce/eliminate the occurrence of subluxations in the hip.

It should be noted that some genetic syndromes may make someone more at risk for hip subluxations, such as Ehlers-Danlos Syndrome, which is a genetic condition that causes loose and hypermobile joints. In these cases, Prolotherapy works well to tighten the loose ligaments and provide stability to the hip, thus reducing the risk or prevalence of subluxations.

The hip capsule, instability, and hip dysplasia

Let’s start this section with a brief understanding of what the hip capsule is. The hip capsule is a soft tissue capsule that surrounds the hip joint. Its main structures include the iliofemoral ligament, ischiofemoral ligament, and pubofemoral ligament. Synovium encircling the femoral head and neck. In the image below we see the pubofemoral and iliofemoral ligaments wrapping the ball and socket as part of the hip capsule.

The hip capsule is so important in preventing instability that surgeons now are recommending capsular repair in the surgical setting because of so many hip instability cases after arthroscopy, especially in cases of hip dysplasia, hip hypermobility, connective tissue disorders, and traumatic or atraumatic instability.

This was suggested in 2015 by doctors at Washington University in St Louis writing in the journal Sports Medicine and Arthroscopy Review (2). Here is what they wrote:

“Recent advances in our understanding of the function of the hip capsule have clarified its importance to normal hip function and kinematics. The iliofemoral ligament is the primary stabilizing structure for controlling anterior translation (frontward movement) and external rotation of the hip and is (damaged) by the arthroscopic intraportal capsulotomy (the removal of hip joint capsule tissue). Microinstability of the hip occurring after surgical trauma (hip arthroscopy) remains a poorly defined clinical entity. In certain at-risk populations, capsular repair should be considered as part of an arthroscopic hip procedure to achieve optimal outcomes and avoid iatrogenic instability (dislocation or microinstability). Despite a lack of conclusive evidence-based indications, we recommend capsular repair in the settings of borderline hip dysplasia (or dysplastic variants such as increased femoral anteversion), hip hypermobility, connective tissue disorders, and traumatic or atraumatic instability.”

Now look again at this 2015 study, specifically “Despite a lack of conclusive evidence-based indications, we recommend capsular repair in the settings of borderline hip dysplasia.” As of this writing in 2015, researchers had not made clear evidence that in patient issues with hip dysplasia, the hip capsule is compromised. Now let’s move forward to 2022.

In March 2022, doctors at Ghent University Hospital in Belgium along with Cambridge University and the University of Antwerp, Antwerp, Belgium wrote in the Orthopaedic Journal of Sports Medicine (4) about the key role the hip’s anterior capsule plays in movement and that during surgery, it should be “handled with care.” In this paper, the focus was on the iliofemoral ligament. The iliofemoral ligament is the strongest ligament in the body.

In mechanical testing, the researchers found that when the iliofemoral ligament is strong and undamaged, the impact and strain on the hip flexor muscles, the iliopsoas, and the sartorius muscles was greatly reduced. Conversely if damaged the ligament could then cause muscle fatigue and spasms as the muscle would have to work harder to stabilize the hip during walking.

The conclusion of this paper comes with suggestions to doctors: “The findings emphasized the key role the iliofemoral ligament plays in hip flexion by working synergistically with the hip musculature. . . .The importance of the contribution of the iliofemoral ligament to the hip flexors warrants careful handling and repair of these ligaments in cases of surgery and structural damage.”

A June 2022 paper in the journal Knee surgery, Sports Traumatology, Arthroscopy (3) investigated the thickness and intra-substance change of the anterior capsule of the hip joint, and compare the difference of the capsular features in patients with different statuses of hip stability. Specifically, the researchers were looking at patients with borderline dysplasia of the hip, femoracetabular impingement, and dysplasia of the hip.

Thirty patients (17 women and 13 men) enrolled in each group (femoracetabular impingement, borderline dysplasia of the hip, and dysplasia of the hip) matched by sex and age were evaluated.
Findings: “Patients with hip dysplasia have a significantly reduced capsular thickness on MRI and delaminated anterior joint capsule, which could be a sequence of instability. The clinical relevance of this study is that capsular thickness and intra-substance changes of the anterior capsule vary which could alter capsular management strategies.”

What is being suggested is that hip instability causes a weakening and thinning of the front of the hip capsule.

1 Cerezal L, Arnaiz J, Canga A, Piedra T, Altónaga JR, Munafo R, Pérez-Carro L. Emerging topics on the hip: ligamentum teres and hip microinstability. European journal of radiology. 2012 Dec 1;81(12):3745-54. [Google Scholar]
2 Nepple JJ, Smith MV. Biomechanics of the hip capsule and capsule management strategies in hip arthroscopy. Sports Medicine and Arthroscopy Review. 2015 Dec 1;23(4):164-8. [Google Scholar]
3 Bai H, Fu YQ, Ayeni OR, Yin QF. The anterior hip capsule is thinner in dysplastic hips: a study comparing different young adult hip patients. Knee Surgery, Sports Traumatology, Arthroscopy. 2022 Jun 10:1-9. [Google Scholar]
4 Duquesne K, Pattyn C, Vanderstraeten B, Audenaert EA. Handle with care: the anterior hip capsule plays a key role in daily hip performance. Orthopaedic journal of sports medicine. 2022 Mar 24;10(3):23259671221078254. [Google Scholar]

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