Yes, Virginia, You May Squat After Your Hip Surgery

Sixty percent of the global population live in one of the 48 countries that comprise Asia—and most squat routinely. Squatting refers to a body position where feet are flat on the ground, knees are bent to the point where the rear-end touches ankles and the person’s knees are spread wide.

It is relaxing. If you grew up doing it, your calf muscles are well stretched and can squat for long periods of time. Anyone, whether born in an Asian culture or not, can (and, given its health benefits, probably should consider doing it) squat. For non-squatters, this writer included, learning to “squat” requires practice, principally to stretch calf muscles.

So, how feasible is squatting after total hip arthroplasty (THA)? A team of researchers from Japan have completed a study about the in vivo kinematics of squatting in order to answer that question.

The investigators gathered data from 543 patients who had undergone primary cementless total hip arthroplasty between February 2011 and December 2015. Their work, “Squatting after total hip arthroplasty: Patient-reported outcomes and in vivo three-dimensional kinematic study,” was published in the December 27, 2022, The Journal of Arthroplasty.

Satoshi Hamai, M.D., Ph.D. an associate professor in the Department of Orthopaedic Surgery, Faculty of Medical Sciences, Kyushu University in Fukuoka, Japan, explained the genesis behind the study to OTW, “Squatting is a fundamental daily activity in many cultures as well as a basic movement for strengthening lower limb muscles. Therefore, an inability to squat after hip surgery could impact younger and more active patients. THA is increasingly being performed in younger patients who require a more active lifestyle. However, few studies have looked at squatting ability after THA, and even less is known about replaced hip biomechanics during squatting to confirm whether squatting can be performed safely.”

According to the authors, the survey—whose final inclusion was 328 patients—was as follows.

1. Each patient was asked if they could squat or not. They were asked to select either:
   1. Yes, ‘easily possible’,
   2. Yes, ‘possible with some support’,
   3. No, ‘impossible’, and
   4. No, ‘have not tried.’
2. Patients who answered, “easily possible” and “possible with some support” were asked when they were able to squat after THA. They selected from these five items:
   1. <1 month,
   2. 1–3 months,
   3. 3–6 months,
   4. 6– 12 months, and
   5. >12 months.
3. Patients who answered “impossible” and “have not tried” were asked to provide one reason from the following six options:
   1. hip pain,
   2. weak muscle strength,
   3. been told not to squat (restriction) by medical staff,
   4. been told not to squat (restriction) by family and acquaintance,
   5. anxiety about dislocation, and
   6. others.

For the kinematic analysis, the researchers collected data from 32 hip replacements in 30 patients (from 211 patients who reported their ability to adopt a squatting position “easily” or “with some postoperative support.”).

The team also reviewed CT scans with, according to the authors, “a 512 × 512 image matrix, a 0.35 × 0.35-pixel dim, and a 1-mm thickness spanning from the superior edge of the pelvis to below the knee joint line. Kinematics of both the hip joint and implant components were analyzed using density-based image-matching techniques, giving them in vivo measurements of 3D joint kinematics based on 2D continuous radiographic images by matching 3D bone and implant models from CT and computer-aided design data, respectively.”

“Patients who could easily squat significantly increased this ability postoperatively,” said Dr. Hamai to OTW. “In 29.5% of the patients there was still no ability to squat after THA; the main reason was anxiety of dislocation (34.2%). Therefore, a patient’s ability to squat may exceed their own expectation.”

“In vivo squatting kinematics seem safe against impingement and subsequent dislocation, but extremely large hip flexion and small cup anteversion remain risks. In particular, anterior liner-to-neck clearance should be maintained, ensuring further unintentional deeply hip flexed, abducted, and internally rotated posture, thus avoiding prosthetic impingement because most dislocations occur in the posterior direction in a posterolateral approach.”

“These data may be beneficial for advising patients after THA regarding postoperative squatting activities in daily life and helping surgeons to understand the effect of an individual’s replaced hip kinematics and component alignment on the liner-to-neck clearance during squatting.”