Hip alignment changes after total knee arthroplasty (TKA) commonly occur as the body adjusts to a new mechanical axis. Often, this realignment corrects pre-existing issues. However, changing the very structure of a knee can alter pelvic tilt, muscle balance, and hip rotation. This article explores the links among spine, hip, and knee alignment, as well as the best ways to manage this condition once it occurs.
The Connection Between Knee Joints and Hip Joints
Hip and knee joints may seem like separate and distinct entities due to their distinct locations in the body. However, a deeper connection does exist between them.
The human body operates in interrelated ways, with each component playing a vital role. Orthopedic surgeons often treat patients for whom hip discomfort triggers knee joint pain and vice versa. This correlation relates to the complex network of muscles, bones, and joints that link these areas. Understanding this connection can lead to more effective strategies for personal trainers working with clients experiencing joint pain, providing relief while also strengthening affected body parts to foster healthier, more functional living.
What Causes Misalignment?
Many individuals experience a significant misalignment of one or both hips following corrective knee surgeries. A number of reasons might elicit this outcome:
- the body moving in a different rhythm for the months/years leading up to knee surgery
- altered gait patterns
- muscle weakness during a lengthy recovery period
Such imbalances may lead to hip, pelvis, and lower back pain as the body adjusts to the new knee joint. We will discuss each of these issues in greater detail.
Marching to a Different Drummer
We often wonder which came first: knee surgery followed by hip pain, or hip pain prior to knee surgery. Both situations can come about, for very different reasons.
People tend to delay undergoing total knee replacement surgery until an orthopedic surgeon tells them they have a “bone-on-bone” situation. During the months or years leading up to the decision to schedule surgery, most individuals unknowingly begin to compensate for knee pain by altering their movement patterns. When knee pain first presents, one may find it easier to limp a bit. Over time, this limp may shift to an alteration in the hip’s angle while walking. Changes in the length of one’s stride can change in subtle ways. Balance issues typically arise, causing the individual to favor one leg over the other, which, over time, can lead to muscle weakness. Compensation with a pelvic tilt may occur both before and after a total knee replacement.
Changes in knee alignment, as pain increases and cartilage erodes, can lead to compensatory movements in the hip joint. The body does this in an effort to maintain stability. This, in turn, can cause muscle tension or pain, often in the hip. Furthermore, after developing these muscle patterns, the presence of a new knee joint may bring about additional changes in alignment. While the knee reconfiguration feels great, the hip joint(s) might need to readjust once again, in a healthier manner, to afford optimal stability to the rest of the body.
Weakness in the gluteus medius and minimus muscles, a common condition following knee surgery, often causes the pelvis to drop on the opposite side of the weak hip, leading to a limp. In this case, specific exercises can facilitate the strengthening of the glutes and core to promote better pelvic stabilization.
Once a knee achieves a healthier alignment, patients often notice increased internal rotation of the hip joint at rest. Getting accustomed to this new, healthier angle may cause pain at first.
Gait Changes Following Surgery
Just as the body compensates prior to a knee replacement, throwing the hips out of alignment, the same situation often presents itself following corrective surgery. In the first few days following a total knee replacement, pain reaches a significant level, often rendering the patient bed-bound for 24-48 hours. Couple this with the need for ice and elevation above the heart to minimize swelling, and we can easily see why the hips may fall out of alignment.
Once ambulatory, individuals may begin to walk differently due to discomfort, balance insecurity, the challenges of learning to walk with a cane/walker, or even taking smaller steps. Such gait changes may lead to muscle strain or joint pain. Just like we learned about prior to surgery, muscles, joints, tendons, and ligaments in other areas of the body all need to compensate. They may eventually get irritated, inflamed, strained, and even torn with overuse. Physical therapists can typically help correct gait changes and any muscle imbalances that may ensue, which are usually the root cause of hip and back pain after a total knee replacement.
Nerve Irritation
Nerve irritation or inflammation may also elicit hip and back pain after a total knee replacement. When the nerves connected to the knee , through the hip and back, are jostled and aggravated during surgery, the patient often feels pain for weeks or months afterward. Referred pain also causes hip discomfort following knee surgery, as the aforementioned nerve irritation creates the sensation of hip misalignment. Symptoms include persistent hip/groin pain, stiffness, a noticeable limp, or instability. With appropriate physical therapy, this condition typically resolves itself over time.
Osteoarthritis
This condition, a specific type of joint inflammation, can affect a multitude of body parts, but most commonly knees, hips, and hands. Once again, owing to poor posturing and gait changes before and/or after knee surgery, the hips, which have borne the brunt of this misalignment, can develop osteoarthritis. This painful condition responds well to oral NSAIDs and stretching.
Medial Opening-Wedge High Tibial Osteotomy (MOHTO)
This unique surgical procedure, often chosen by younger/active patients seeking to delay the need for a total knee replacement, treats medial compartment knee osteoarthritis (pain on the inner side of the knee). The procedure actually realigns the knee, shifting weight away from the damaged medial (inner) compartment to the healthier lateral (outer) compartment.
One research study included 27 patients who had successfully undergone MOHTO surgery. A positive correlation was observed between the magnitude of the necessary correction at the knee and subsequent changes in hip alignment. Interestingly, age, weight, height, and BMI had no significant influence on this correlation.
Pain associated with such hip malalignment most likely comes about due to an alteration in the weight-bearing portion of the femoral head and the function of the abductors. Some scientists recommend that surgeons assess the hip joint prior to planning MOHTO surgery.
Hip Strengthening a Key Part of Post-Op Physical Therapy
As our general population ages, orthopedic surgeons see an increasing incidence of knee osteoarthritis and total knee replacement surgery. Sadly, many patients retain post-operative weakness in the quadriceps and hip abductors for a period extending up to 3 years. The current literature reports that results on the effectiveness of rehabilitation programs that include hip strengthening exercises remain contradictory and controversial. Here we look at the results of the first meta-analysis study on the efficacity of hip strengthening exercises following total knee arthroplasty.
When compared to healthy, age-matched controls, some patients report chronic muscular weakness, continued daily functional challenges, and persistent post-operative pain, despite exhibiting what their doctors would call “clinical improvement.” These patients perform worse than expected on multiple functional outcomes; they also tend to report struggling more with activities of daily living. To meet this growing demographic, postoperative rehabilitation programs have begun to address these functional deficits and persistent muscular weakness.
In the past, a typical post-operative rehabilitation program focused on helping the patient regain quadriceps strength. Despite their efforts, these patients still find that functional limitations persist long after their physical therapy comes to an end. New evidence from this study suggests that hip abductor strength can affect physical function after total knee replacements, and that increasing hip strength following those surgeries may improve patients’ outcomes. Additionally, patients have demonstrated that hip abductor strength correlates more strongly with functional performance than quadriceps strength. Hip strengthening programs also indicate a more favorable improvement in a patient’s ability to stand on 1 leg.
Personal trainers often encounter clients who have recently completed their course of physical therapy following knee replacement surgery. Knowing that hip abductor strength figures prominently in one’s recovery, they can try to incorporate more of these exercises in the client’s workout program. In addition, this population almost universally needs to concentrate on balance issues, but especially following joint replacement surgery. Personal trainers can include balance protocols, such as 2-legged and single-leg stances.
Hip realignment following knee surgery is a common and often temporary consequence of the body adapting to a new mechanical structure and gait pattern. Because the spine, pelvis, hips, and knees function as an interconnected kinetic chain, even positive surgical changes can create short-term imbalances elsewhere in the body. Fortunately, with proper rehabilitation, gait retraining, balance work, and focused strengthening of the hip and core musculature, most patients experience significant improvement in both comfort and functional movement. Personal trainers, physical therapists, and healthcare professionals all play an important role in helping individuals regain stability, confidence, and long-term joint health following knee surgery.
References
gpoa.com/blog/hip-pain-and-knee-pain-what-s-the-connection#:~:text=Similarly%2C%20knee%20problems%20can%20alter,effective%20in%20providing%20pain%20relief.
allianceptp.com/hip-and-back-pain-after-knee-replacement/#:~:text=When%20a%20nerve%20is%20affected,nerve%20damage%20or%20an%20infection.
pmc.ncbi.nlm.nih.gov/articles/PMC10126093/#:~:text=Conclusion,clinical%20significance%20of%20this%20study.
.aofoundation.org/trauma/about-aotrauma/blog/2023_04-blog-open-wedge-high-tibia-osteotomy
pmc.ncbi.nlm.nih.gov/articles/PMC11195033/
pmc.ncbi.nlm.nih.gov/articles/PMC3532632/
