Demographic and clinical characteristics by outcome
| Positive outcome* | Negative outcome† | P value‡ | |
| Age in years, mean (SD) | n=162 63.3 (15.0) | n=103 65.8 (15.5) | 0.20 |
| Sex | |||
| Male | 64/162 (39.5%) | 32/103 (31.1%) | 0.17 |
| Female | 98/162 (60.5%) | 71/103 (68.9%) | |
| Baseline Pain Score (0–10, mean, SD) | n=154 6.6 (2.0) | n=100 7.3 (1.9) | 0.01 |
| Duration of pain (years, SD) | n=122 7.2 (7.4) | n=79 6.9 (5.8) | 0.74 |
| Obese | 93/151 (61.6%) | 49/99 (49.5%) | 0.06 |
| Non-obese | 58/151 (38.4%) | 50/99 (50.5%) | |
| Disability or worker’s compensation§ | 9/161 (5.6%) | 10/102 (9.8%) | 0.20 |
| Not on disability or WC | 152/161 (94.4%) | 92/102 (90.2% | |
| Opioid use | 0.04 | ||
| None | 106/161 (65.8%) | 53/103 (51.5%) | REF |
| <90 oral MSO4 equivalents/d | 50/161 (31.1%) | 42/103 (40.8%) | 0.053 |
| >90 oral MSO4 equivalents/d | 5/161 (3.1%) | 8/103 (7.8%) | 0.050 |
| Coexisting psychiatric condition | 0.02 | ||
| None | 108/162 (66.7%) | 60/103 (58.3%) | REF |
| Anxiety | 14/162 (8.6%) | 6/103 (5.8%) | 0.61 |
| Depression | 16/162 (9.9%) | 26/103 (25.2%) | <0.01 |
| Other | 4/162 (2.5%) | 3/103 (2.9%) | 0.70 |
| Multiple | 20/162 (12.3%) | 8/103 (7.8%) | 0.46 |
| Prior knee surgery | 70/160 (43.8%) | 32/101 (31.7%) | 0.053 |
| No prior knee surgery | 90/160 (56.3%) | 69/101 (68.3%) | |
| Etiology | |||
| Soft-tissue injury | 126/157 (80.2%) | 88/101 (87.1%) | 0.47 |
| Traumatic arthritis | 29/157 (18.5%) | 13/101 (12.9%) | |
| Multiple | 2/157 (1.3%) | 0/101 (0.0%) | |
| Coexisting pain condition | |||
| None | 67/138 (48.6%) | 45/89 (50.6%) | 0.89 |
| Only one | 66/138 (47.8%) | 40/89 (44.9%) | |
| Multiple | 5/138 (3.6%) | 4/89 (4.5%) | |
| Pain referral pattern | |||
| Medial | 34/101 (33.7%) | 21/60 (35.0%) | 0.86 |
| Central | 43/101 (42.6%) | 27/60 (45.0%) | |
| Lateral | 24/101 (23.7%) | 12/60 (20.0%) | |
| Smoker | 28/156 (18.0%) | 21/99 (21.2%) | 0.52 |
| Non-smoker | 128/156 (82.1%) | 78/99 (78.8%) | |
| Kellegren-Lawrence grade <2¶ | 55/102 (53.9%) | 31/78 (39.7% | 0.06 |
| Kellegren-Lawrence grade >2 | 47/102 (46.1%) | 47/78 (60.3%) |
*Positive outcome defined as ≥30% pain relief lasting at least 3 months.
†Negative outcome defines as <30% pain relief or not lasting for 3 months.
‡Univariable logistic regression analysis performed.
§For active duty personnel, includes the military equivalent (medical board evaluation).
¶Kellegren-Lawrence system is used to classify severity of osteoarthritis using five grades from 0-4, with higher numbers indicated greater degeneration.
**P-value compares positive outcome vs negative outcome.
MSO4, morphine sulfate; WC, worker’s compensation.