Table 2 Results for patient-reported outcome measures (PROM)

 Sveikata [33]

Geriatr Orthop Surg Rehabil

2017

314

< 75, ≥ 75

Post operation 1 year: no difference in pain (P = 0.592), stiffness (P = 0.729), or function (P = 0.082) according to WOMAC and SF-12 physical (P = 0.082) and mental (P = 0.559) health score

 Escobar [31]

J Eval Clin Pract

2017

492

No difference between minimal clinically important difference (MCID)/patient acceptable symptom state (PASS) (P = 0.5)

 Lizaur-Utrilla [35]

Knee Surg Sport Traumatol Arthrosc

2016

≤ 55: 61

60–70: 61

≤ 55, 60–70

Post operation 5 years, there were no significant differences between groups in KSS knee or function, WOMAC pain or function, or SF-12 physical or mental. However, there were better results in younger patients for KSS function (P = 0.018), WOMAC function (P = 0.028), SF-12-physical (P = 0.001) and SF-12-mental (P = 0.035), although clinically relevant

 Maempel [40]

Acta Orthop

2015

3144

< 75, 75–80, > 80

Post operation 5 years: all groups showed similar substantial improvements in AKS, which were maintained (all P < 0.001)

 Kuo [44]

J Orthop Surg Res

2014

1024

< 80, ≥80

Both groups (≥ 80, < 80) had improved in the KSS (≥ 80: 86, < 80: 88), KSFS (≥ 80: 87, < 80: 89), WOMAC (≥ 80: 15.0, < 80: 14.6) scores

 Hamilton [47]

BMJ Open

2013

4709

Median age of satisfied group is 70.3 and unsatisfied group is 70.0 (P = 0.829)

 Kennedy [48]

Clin Orthop Rel Res

2013

≥80: 438

< 80: 2754

< 80, ≥80

There was no difference in pain scores at 3, 5, and 10 years between the ≥ 80 years group and

< 80 years group. The KSS was comparable between groups at year 5, but the KSFS was lower in the octogenarians

 William [50]

Bone Joint J

2013

2456

< 55

55–64, 65–74, 75–84, ≥ 85

Postoperative scores were comparable across age groups, but a linear trend for greater postoperative improvement in OKS and EQ-5D was seen with decreasing age (P < 0.033)

 Clement [53]

Bone Joint J

2011

677

< 80, ≥ 80

Post operation 1 year: no significant difference was observed between the groups in the mean improvement in OKS (95% CI − 0.65 to 2.94, P = 0.16)

 Pitta [25]

J Arthroplast

2019

3693

For the KOOS pain, KOOS activity, and LEAS outcomes, the divergence point occurred at age 68 years. For the KOOS symptom outcomes, the divergence point occurred at age 70 years.

 Elmallah [34]

J Knee Surg

2016

278

< 55, 55–74, > 74

For KSS objective, patiemts 75 years and older had the highest mean score at final follow up (97 points). In KSS function, the < 55-years group had highest scores at 2-year (90 vs. 87 vs. 75 points) and 5-year follow up (96 vs. 88 vs. 72 points). For SF-36 and LEAS, the cohorts 75 years and older had the lowest mean scores at various time points. In the mental component, those < 55 years had the lowest scores postoperatively

 Townsend [29]

J Knee Surg

2018

356

< 50, 50–59,

60–69, 70–79,

> 79

Postoperative WOMAC and overall, pain, and function OKS significantly differed among the age groups (P  < 0.05), with patients younger than 60 years reporting the worst scores in the postoperative time period. Older patients reported better preoperative overall, pain, and function scores and greater post-TKA outcomes than younger patients

 Merle-Vincent [54]

Joint Bone Spine

2011

264

≤ 70,

> 70,

Age older than 70 years at surgery was associated with a higher satisfaction rate (odds ratio of age ≥ 70 years is 3.9 [1.1–14.3]; P = 0.038)

 Murphy [14]

Bone Joint J

2018

2838

< 80,

≥ 80

SF-12 PCS, coefficient of ≥ 80-group is − 4.46 (− 6.18, − 2.73), P < 0.001

 KJ Oh [26]

Aging Clin Exp Res

2018

79

65–70,

≥ 80

The octogenarian patient group had significantly inferior outcomes for WOMAC and SF-36 score compared to the sexagenarian patient group (P = 0.009 and P = 0.022, respectively)

 Naylor [28]

Arthritis Care Res

2018

1289

Post operation 3 years: younger age (P = 0.0018) was significantly associated with regular physical activity

 Razak [36]

J Bone Joint Surg Am

2016

3062

Younger age KSS predicted a good outcome at 5 years (OKS: OR of age is 2.66 (2.61–2.71), SF-36 PCS: OR of age is 2.64 (2.59–2.67))

 Singh [57]

Osteoarthr Cartil

2010

7139

61–70,

71–80,

> 80

Significantly predictors of overall moderate–severe activity limitation 2-years post-TKA was age 71–80 (OR: 2.1 [1.5, 2.8]) and age > 80 (OR: 4.1 [2.7, 6.1]) vs, age ≤ 60 years, and 5 years post-TKA was age 71–80 (OR: 2.4 [1.7, 3.5]) and age > 80 (OR: 4.7 [2.8, 7.9]) vs. age ≤ 60 years

  Skinner [37]

Ann R Coll Surg Eng

2016

67

70–79,

90–99

For preoperative OKS no significant difference between nonagenarians and control group

  Lange [27]

J Arthroplast

2018

1058

18–55,

65–75

Distribution of satisfaction responses was shifted toward greater satisfaction in older patients (P < 0.001). Younger patients reported greater knee-related dysfunction and higher activity levels preoperatively and postoperatively (P = 0.0002)

  Haynes [32]

Knee

2017

≤ 55: 82

65–75: 85

≤55,

65–75

The younger patient cohort reported substantially lower preoperative clinical outcome scores. WOMAC pain (12.1 points, P < 0.01), and WOMAC physical function. (6.9 points, P < 0.01) improvement was noted; however, WOMAC pain score remained lower among the younger patient cohort

  Clement [19]

Arch Arthop Trauma Surg

2018

2589

< 55, 55 ≤

The younger age group was twice as likely to be dissatisfied with their overall outcome and pain relief, with only 83% and 85% being satisfied compared to 92% and 91% in the older age group, respectively