BACKGROUND: Inflammation and subsequent fibrosis, adhesions, or plicae may limit normal capsular compliance and decrease volume capacity of the knee. HYPOTHESIS: Patients with fibrosis, anterior interval scarring, adhesions, or palpable painful plicae will have decreased knee volumes when compared to controls, and selective arthroscopic releases will restore volume to normal levels. STUDY DESIGN: Descriptive laboratory study and cohort study; Level of evidence, 2. METHODS: In part I, knee volume and pressure were recorded in 14 fresh-frozen human cadaveric knees, and the maximum volume capacity was identified before capsular disruption. In part II, 49 patients undergoing arthroscopy were divided into 2 groups based on intraoperative volume assessment at 50 mm H(2)O pressure: group 1 (n = 20) with normal volume (<1 standard deviation below the mean established in part I) and group 2 (n = 29) knees with deficient volume (>1 standard deviation below mean). Group 2 underwent volume-changing procedures such as lysis of adhesions, anterior interval release, and plica resections, while group 1 underwent volume-neutral procedures including meniscal or chondral surgery. The knee volume was then reassessed after arthroscopy. RESULTS: The average volume capacity of the knees in the cadaveric study was 87.5 ± 21.7 mL (range, 50-120 mL). There was no statistical difference between the presurgical (98.9 ± 29.8 mL) and postsurgical volumes (99.4 ± 29.1 mL) in group 1; P = .65. The presurgical volume in group 2 (46.1 ± 13.0 mL) was significantly lower than group 1 (P = .001). The group 2 volume increased to 78.5 ± 24.2 mL after surgery (P = .001), with an average change in volume of 75.5%. The mean change in volume after surgery was significantly greater in group 2 (32.3 mL) versus group 1 (0.45 mL) (P = .001). At 1-year follow-up, the mean Tegner score in the volume-compromised group 2 increased from 2.0 ± 1.4 preoperatively to 4.0 ± 2.0 postoperatively (P = .01), the Lysholm score increased from 45.0 ± 24.0 preoperatively to 76.8 ± 25.4 postoperatively (P = .003), and the average Short Form-12 quality of life score increased from 32.4 ± 8.7 preoperatively to 45.0 ± 11.0 postoperatively (P = .005). CONCLUSIONS: The average volume of the human knee in this study was between 65 and 110 mL (±1 standard deviation of mean of 87.5 mL). Although patients with chronic knee pain may have pain from multiple sources, some may have diminished knee volume, and selected arthroscopic releases can restore knee volume to near-normal levels.
BACKGROUND: Inflammation and subsequent fibrosis, adhesions, or plicae may limit normal capsular compliance and decrease volume capacity of the knee. HYPOTHESIS: Patients with fibrosis, anterior interval scarring, adhesions, or palpable painful plicae will have decreased knee volumes when compared to controls, and selective arthroscopic releases will restore volume to normal levels. STUDY DESIGN: Descriptive laboratory study and cohort study; Level of evidence, 2. METHODS: In part I, knee volume and pressure were recorded in 14 fresh-frozen human cadaveric knees, and the maximum volume capacity was identified before capsular disruption. In part II, 49 patients undergoing arthroscopy were divided into 2 groups based on intraoperative volume assessment at 50 mm H(2)O pressure: group 1 (n = 20) with normal volume (<1 standard deviation below the mean established in part I) and group 2 (n = 29) knees with deficient volume (>1 standard deviation below mean). Group 2 underwent volume-changing procedures such as lysis of adhesions, anterior interval release, and plica resections, while group 1 underwent volume-neutral procedures including meniscal or chondral surgery. The knee volume was then reassessed after arthroscopy. RESULTS: The average volume capacity of the knees in the cadaveric study was 87.5 ± 21.7 mL (range, 50-120 mL). There was no statistical difference between the presurgical (98.9 ± 29.8 mL) and postsurgical volumes (99.4 ± 29.1 mL) in group 1; P = .65. The presurgical volume in group 2 (46.1 ± 13.0 mL) was significantly lower than group 1 (P = .001). The group 2 volume increased to 78.5 ± 24.2 mL after surgery (P = .001), with an average change in volume of 75.5%. The mean change in volume after surgery was significantly greater in group 2 (32.3 mL) versus group 1 (0.45 mL) (P = .001). At 1-year follow-up, the mean Tegner score in the volume-compromised group 2 increased from 2.0 ± 1.4 preoperatively to 4.0 ± 2.0 postoperatively (P = .01), the Lysholm score increased from 45.0 ± 24.0 preoperatively to 76.8 ± 25.4 postoperatively (P = .003), and the average Short Form-12 quality of life score increased from 32.4 ± 8.7 preoperatively to 45.0 ± 11.0 postoperatively (P = .005). CONCLUSIONS: The average volume of the human knee in this study was between 65 and 110 mL (±1 standard deviation of mean of 87.5 mL). Although patients with chronic knee pain may have pain from multiple sources, some may have diminished knee volume, and selected arthroscopic releases can restore knee volume to near-normal levels.
Authors: Jacob D Mikula; Erik L Slette; Kimi D Dahl; Scott R Montgomery; Grant J Dornan; Luke O'Brien; Travis Lee Turnbull; Thomas R Hackett Journal: J Exp Orthop Date: 2017-12-19