Prevalence and factors associated with symptomatic knee osteoarthritis in golfers: A cross-sectional study among professional golfers in Kenya

INTRODUCTION

Golf is a low-impact sport, whose level of performance is not limited by a person’s age and has significantly gained popularity worldwide and in Kenya.^[1-3] A golfer’s current skill level is measured as one’s handicap. A lower handicap allows fewer shots per hole thus implying greater skill.^[4] Professional golfers are defined by a handicap of 0 or negative and they play significantly more frequently and for a longer duration than amateurs thus are considered distinct patient groups with different sports profiles.^[5,6]

The loading on the tibiofemoral joint during the golf swing causes stresses in the axial and coronal planes imparting strain to both intra- and extra-capsular structures, for example, ligaments, menisci, etc.^[7] High compressive and torsional forces have been described in the knee during the golf swing.^[8,9] Articular cartilage tolerance is exceeded by the excess stresses and abnormal loading contributing to joint degeneration.^[10]

Knee injuries involving the knee ligaments, menisci, and cartilage have also been linked to knee OA.^[10,11] A systematic review of golf injuries reported knee injury prevalence rates ranging from 3% to 18% among both advanced and novice players^[12,13] which is comparable to prevalence rates in high-impact sports such as soccer and basketball.^[12] Studies suggest that this combined with the abnormal loading conditions, regardless of skill level can result in progressive joint degeneration.^[12] The incidence and prevalence of KOA have been investigated and reported for other sports such as soccer, rugby, and athletics with minimal data about golf.^[14,15] During sports, the musculature around the joints influences the vertical ground reaction force during the impact phase and is seen to protect joints from supraphysiological loading;^[16] therefore, conditioning exercises increase the likelihood of the golfer to protect their joints from increased loading and hence accordingly reduce the risk of joint injury.^[17] Strategies that decrease joint contact forces while still enabling muscle strengthening and conditioning minimize joint loads and beneficial in decreasing pain and improving function. These include cycling, swimming, or other aquatic exercises.^[18,19]

The Knee Injury and Osteoarthritis Outcome Score (KOOS) is a validated patient-administered questionnaire used to assess the participants’ impression about their knee symptoms. Patients are said to have significant clinical symptoms requiring further evaluation if they have a score of <85% in two or more of the subscale parameters.^[20,21] The Kellgren and Lawrence Grading System (K&L) is a radiological classification of the severity of knee OA on plain radiographs based.^[22] A K&L score of 2 and above signifies definite established OA.^[21]

There is a paucity of high evidence studies on golfers that are well designed to include radiological and functional evaluation of the knee based on internationally validated measures as the adequate assessment for KOA among golfers.

MATERIALS AND METHODS

RESULTS

Outcome data

More than half had a BMI >25 kg/m², that is, 30% with a BMI of 25–29.9, that is, overweight, and 26% >30 kg/m², that is, obese. [Figure 1] illustrates the BMI distribution. Only two participants were left handed, that is, 96% of the participants having the left knee as the lead knee and the right knee as the trail knee.

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Figure 1:

Body mass index of participants.

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The mean duration of active golf participation was 16.5 years with a SD = 4.2 years, that is, with 74% participating 5 or more days a week. [Figure 2] illustrates the distribution of duration of active golf participation and [Figure 3] shows the frequency of active play.

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Figure 2:

Duration of active golf participation.

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Figure 3:

Frequency of golf participation on a weekly basis.

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Thirty-seven participants, that is, 74% described their regularity of performing pre-conditioning exercise, for example, stretches and warm up as always^[24] and sometimes^[10] before a golf game or practice round of which only 30% was for a duration of more than 10 min. More than half of the participants never^[15] or rarely^[14] actively engaged in any other form of physical exercise other than golf at the time of the study.

About 14% of the participants reported an incident of golf-related knee injury of which more than half implicated the repetitive nature of the golf swing as the cause of the injury. Uneven terrain was cited as another reason. About 64% participated in other sporting activities before the start of golf with only three sustaining knee injuries with the prior sports participation.

Main results

Eighteen out of the 100 knees analyzed scored <85% in two or more of the subscale parameters of the KOOS. [Figures 4 and 5] illustrate the KOOS scores for the right and left knees, respectively.

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Figure 4:

Knee Injury and Osteoarthritis Outcome Score for the right knee.

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Figure 5:

Knee Injury and Osteoarthritis Outcome Score for the left knee.

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A BMI of more than 25 kg/m² and prolonged duration of active golf participation were found to have a OR of 1.107 and 1.144, respectively, as related to the presence of symptomatic osteoarthritis with P = 0.3481 and 0.2809. Age as a factor had an OR of 1. [Table 1] illustrates the logistic regression model determining the relationship between symptomatic knee osteoarthritis and indicated factors.

Table 1: Correlation of the relationship between symptomatic knee osteoarthritis and specified participant characteristics.

Factor	Odds ratio	95% confidence interval	P-value
Duration of active golf participation	1.144	0.917–1.528	0.2809
Body mass index	1.107	0.893–1.385	0.3481
Age	1	0.067–1.007	0.9798

According to the Kellgren and Lawrence Grading Scale, the severity of KO for the 18 knees subjected to plain radiograph evaluation, 72% had a K&L score of Grade 2 and above.

DISCUSSION

Half of participants in this study were 40 years and above, that is, median age (IQR) of 41 (34–49). This correlates with the average age of professional golfers worldwide as reported by Baker et al.^[5] The estimated median age at knee OA diagnosis in the US is 55 years^[25] but has been shown to occur up to 10 years earlier in sports participants, particularly at an elite level, thus the professional golfers at this age due to their high skill play level may be at risk of symptomatic KOA.^[15,26,27]

More than half of the participants are overweight and obese. Several studies have shown that there is a positive correlation between increased body weight and the development of osteoarthritis particularly in weight-bearing joints such as the knee.^[24] Combining sports participation and increased body weight, the relative contributions of etiological fraction relating to the development of osteoarthritis are estimated to be 55% for sports participation and 15% for being overweight.^[28,29] This, therefore, puts the overweight and obese professional golfers studied here at a higher risk of developing KOA.

The relationship between the development of knee osteoarthritis and involvement of elite sports for a prolonged duration was described by Vingard et al. in two publications analyzing OA of the hip in women and its relationship to physical loading due to sporting activities. The men who had high total number of hours had a 4.5 times ([CI] 2.7–7.6) greater risk of developing osteoarthritis at the hip compared with those with low exposure.^[30,31] Spector et al. also showed an increased risk of both knee and hip OA in long-distance runners and tennis players with prolonged years of training 15 and 19 years, respectively, and also with increased frequency of training, that is, 25 km/week and 5.2 h/week, respectively.^[27] Therefore, the prolonged involvement in golf at a professional level and high frequency as reported among the study participants may lead to an increased risk for development of KOA.

The recommended pre-game conditioning duration is at least 10 min and this facilitates proper muscle and ligament stretching useful in maintenance of proper joint mechanics and alignment thus less likelihood of injuries.^[7,12] The results also show that only 16% of the professional golfers recruited in this study regularly participate in other forms of physical activities other than golf. Muscular contraction is known to be protective to excessive knee loads applied across the knee joint; therefore, resistance and conditioning training of the muscles around the knee are important and have been particularly shown to contribute positively to functional and symptomatic outcome.^[18,32]

Knee injury due to sports participation is a known risk factor for the development of knee osteoarthritis due to damage to joint stabilizing structures such as the ACL and meniscus which alter knee joint biomechanics, cause instability, abnormal loading, and eventually KOA. The results here present a prevalence of 14% when it comes to golf-related knee injury among professional golfers in Kenya a value that is reflective of the work done by Baker et al. in a systematic review in 2017. He reported an injury rate that varied from 3 to 18% with a career rate among professionals being noted at 5.5–15% proposing a by and large higher injury rate in the professionals when contrasted with the amateurs.^[13,33,34]

This prevalence of 18% is comparable to the prevalence rates of KOA in contact sports as Vannini et al. published in 2016 illustrating that OA incidence in current and former soccer players ranges between 16 and 80%^[10] while Driban et al.^[35] showed an overall knee OA prevalence in sports participants as 7.7% with high-impact sports such as football having higher prevalence. Therefore, a prevalence of 18% for golf is akin to that of high-impact sports such as soccer.

The factors that correlate most with the prevalence of KOA among the study participants were found to be duration of active golf participation (OR – 1.114, CI – 0.917–1.528) and BMI (OR – 1.107, CI – 0.893–1.385). They were, however, not statistically significant, that is, P = 0.2809 and 0.3481, respectively. Of the participants found to have symptomatic knee osteoarthritis, 72% were graded as established OA based on a Kellgren and Lawrence classification of Grade 2 and above.

CONCLUSION

Golf albeit a low-impact sport presents a prevalence of symptomatic knee osteoarthritis of 18%, majority of whom had established knee osteoarthritis which is comparable to other sports. This is due to the biomechanical demands on the golf swing on the knee joints compounded by and increased risk of knee injury. The main factors associated with symptomatic knee osteoarthritis were found to be a BMI greater than 25 and longer duration of active participation in golf although both were not found to be statistically significant.