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Research Review By Jessica Sleeth ©

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Date Posted:

February 2011

Study Title:

Effect of quadriceps strength and proprioception on risk for knee osteoarthritis

Authors:

Segal NA, Glass NA, Felson DT et al.

Author's Affiliations:

Department of Orthopaedics and Rehabilitation, Radiology, and Epidemiology, University of Iowa, Iowa City, IA; Boston University, Boston, MA; King’s College London, London, England; University of California at San Francisco, San Francisco, CA; University of Alabama at Birmingham, Birmingham, AL.

Publication Information:

Medicine & Science in Sports and Exercise 2010; 42(11): 2081-2088.

Background Information:

In the human body, the weight-bearing joint most commonly affected by osteoarthritis (OA) is the knee (1). There is currently no cure for OA, which is both a biomechanical and biochemical disease. A person with knee OA is more likely to suffer from slower performance and require functional modifications in their life, compared to someone without knee OA (2). In a recently published study, the authors found that increased knee extensor strength decreased the risk of developing symptomatic knee OA in women (3). Yet, the authors did not find an association between quadriceps strength and incident radiographic knee OA.

Similarly, numerous other studies have found that decreased quadriceps strength and proprioception are linked to knee OA (article references: 9-11, 13, 17, 23, 38, 39). It is hypothesized that there exists more than one predisposing factor that leads to knee OA. Protective factors are currently unknown, however, improved sensorimotor function (quadriceps strength and proprioception) may act to protect against incident radiographic or symptomatic knee OA.

Stability at the knee joint is dependent on internal forces exerting themselves at sufficient magnitudes to counteract any external forces acting at the knee. In essence, the quadriceps is a crucial muscle group that provides dynamic stability by absorbing load applied to the knee joint. Therefore, if the quadriceps muscles are weakened it may cause increased stress to the knee joint. Proprioception also contributes to dynamic joint stability through coordinating the stress response of the quadriceps, hamstrings, and other associated muscles. Joint position sense (JPS), is a component of proprioception that was specifically investigated in this study. Decreased proprioception, particularly with age, may be associated with increased knee OA (4). However, a recent cross-sectional study reported that knee OA diminished joint proprioception, thus, the temporal relationship between knee OA and proprioception remains unknown.

The authors recommend future longitudinal studies to further examine the temporal relationship between proprioception and knee OA. This study was undertaken to determine whether the combination of knee extensor strength and knee JPS protect against the development of incident radiographic or incident symptomatic knee OA.

Pertinent Results:

Incident radiographic whole knee OA:

After screening for eligibility and pain during trial strength tests, 2276 (58.2% women) knees were used in this portion of the study. The mean age was 61.2 (SD 7.9) years old and mean BMI was 29.4 (SD 5.1). Baseline mean joint position sense (JPS) correlated with age and presence of knee pain, however JPS variance (difference between extending leg to specific angle, then repeating action without watching leg movement) was only correlated with the presence of knee pain. The authors adjusted for age, sex, BMI, history of knee injury or surgery, and physical activity level at baseline.

Yet, no relationship was found between knee extensor strength, mean JPS, and incident radiographic knee OA. When analyzed individually, high knee extensor strength and strong JPS were not found to be protective factors against incident radiographic knee OA. In a continuous variable analysis, the relationship between knee extensor strength and JPS was not associated with incident radiographic knee OA. BMI appears to be the only predictor of incident radiographic knee OA.

Incident symptomatic whole knee OA:

Again, after screening for eligibility and pain, 3166 knees (58.6% women) were included in this portion of the study. The mean age was 62.2 (SD 8) years old and the mean BMI was 30.0 (SD 5.4). JPS (baseline and variance) scores decreased with age, low physical activity levels, and increased pain. 298 knees developed incident symptomatic knee OA during the trial. The authors found that those with higher knee extensor strength were at a lower risk of developing incident symptomatic knee OA than those with less strength, regardless of JPS (adjusted for age, BMI, sex, knee injury/surgery, and physical activity level).

The same relationship exists when the variables were analyzed individually. However, there was no relationship reported between mean JPS and incident symptomatic knee OA. Significant associations were reported with age, BMI, history of surgery, and incident symptomatic knee OA. In a continuous variable analysis, an association between knee extensor strength and JPS was not predictive of incident symptomatic knee OA.

Clinical Application & Conclusions:

The authors report that increased knee extensor strength is associated with decreased risk for incident symptomatic knee OA, but not incident radiographic knee OA. The results are consistent with findings in the MOST study (3).

Sensorimotor dysfunction was hypothesized to increase risk of developing OA in the knee. As previously discussed, the quadriceps are the main dynamic stabilizer muscle group of the knee. Therefore, the authors hypothesized that decreased proprioception and quadriceps weakness could increase the risk of damage to the knee joint. However, it is reported that strength, regardless of JPS score (measure of proprioception), is a protective factor against incident symptomatic knee OA. This finding suggests that decreased proprioception (as per this study) does not increase the risk of radiographic knee OA or symptomatic knee OA.

Study Methods:

Study participants were enrolled through the Multicenter Osteoarthritis (MOST) study, which is a longitudinal cohort study of risk factors for knee OA. Participants were recruited using mass mailings and advertisements, followed by eligibility screening by telephone (for known risk factors such as, knee injury/surgery and obesity). The MOST study consists of 3026 men and women, 50-79 years old, who have knee OA or known risk factors. Multivariate logistic regression was completed using SAS software, version 9.1. The portion of the study investigating incident radiographic knee OA required 2276 knee tests for 80% power and the incident symptomatic knee OA required 3166 knee tests for 80% power.

Exclusion criteria:
  • history of (or planned) bilateral knee replacement
  • non-resected cancer (exception: non-melanoma skin cancer)
  • previous chemotherapy or radiation therapy
  • rheumatologic disease
  • plans to move out of study catchment area within three years
During the study, participants were excluded if knee pain prevented completion of the knee extensor strength tests. Participants were eligible for the incident radiographic portion of the study if they did not have knee OA at baseline and for the incident symptomatic portion if they did not have knee OA and frequent knee symptoms at baseline.

Measurements:
  • Body Mass Index
  • Knee extensor strength measurements – concentric force assessed with a Cybex 350 computerized isokinetic dynamometer. Participants were allowed three practice trials (using 50% effort). Following the practice trials, four trials were completed to obtain peak torque. If participants reported pain that prevented maximal effort during the strength test, they were excluded from the study.
  • JPS – this measurement began with participants extending their leg to a specific angle, holding for five seconds, and then relaxing. Immediately after, the participant is requested to replicate the same angle without watching their leg. The difference between the first and second angles was recorded. Two practice trials were allowed, followed by 10 knee flexion exercises that were measured with an electrogoniometer.
  • Radiographic knee OA assessment – Weight-bearing and fixed-flexion posteroanterior and lateral radiographs of knees were taken at baseline and at 30 months.
  • Knee symptoms – participants were surveyed about knee pain, stiffness, or aching at baseline (twice – once by telephone and once at a clinic visit) and at 30 months
  • Physical activity and medical history – Participants were screened using the Physical Activity Scale for the Elderly, at baseline.

Study Strengths / Weaknesses:

  • When measuring JPS of the knee joint, study methods included non weight-bearing trials to avoid a selection bias against participants with standing joint pain. Other studies have conducted trials with participants standing and thus, weight-bearing for the trials. In this study, the results may not reflect true daily physical function. Thus, it is possible that taking the measurements in a seated position may have influenced the lack of association between incident knee OA and JPS.
  • The authors speculate that use of magnetic resonance imaging (MRI), which is a more sensitive screening procedure, may have identified more cases.
  • Intermittent symptoms of symptomatic knee OA may not have been disclosed at baseline or 30 month telephone and clinic visits. If the study had been longer in duration, it is possible that more cases would have been identified. The authors recommend more frequent knee extensor strength measurements and a longer duration of the study.
  • The study included measurements of only the right knee, therefore, it is possible that cases were missed in left knees. However, previous studies have reported that decreased proprioception is generally present in both joints and not unilaterally.
  • The MOST study was comprised of participants with or at high risk for knee OA such that, results may not be generalizable.

Additional References:

  1. Davis MA. Epidemiology of osteoarthritis. Clin Geriatr Med. 1988; 4(2):241-55.
  2. Ling SM, Fried LP, Garrett ES, Fan MY, Rantanen T, et al. Knee osteoarthritis compromises early mobility function: The Women’s Health and Aging Study II. J Rheumatol. 2003; 30(1):114-20.
  3. Segal NA, Torner JC, Felson D, et al. Effect of thigh strength on incident radiographic and symptomatic knee osteoarthritis in a longitudinal cohort. Arthritis Rheum. 2009; 61(9):1210-7.
  4. Bullock-Saxton JE, Wong WJ, & Hogan N. The influence of age on weight-bearing joint reposition sense of the knee. Exp Brain Res. 2001; 136(3):400-6.

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