Proprioception protects joints against injurious movements and is critical for joint stability maintenance under dynamic conditions. Knee replacement effect on proprioception in general remains elusive. This study aimed to evaluate the changes in proprioceptive performance after knee replacement; comparing Total (TKA) to Unicompartmental Knee Arthroplasty (UKA).

Thirty-four patients with osteoarthritis were recruited; 15 patients underwent TKA using the AGC prosthesis and 19patients underwent UKA using the Oxford prosthesis. Both cruciate ligaments were preserved in the UKA group, while only the PCL was preserved in TKA patients. Patients’ age was similar in both groups.> Joint Position Sense (JPS) and postural sway were used as measures of proprioception. Both groups were assessed pre- and 6 months post-operatively in both limbs. JPS was measured as the error in actively and passively reproducing five randomly ordered knee flexion angles between 30 and 70°using an isokinetic dynamometer. Postural sway (area and path) was measured during single leg stance using a Balance Performance Monitor. Functional outcome was assessed using the Oxford Knee Score (OKS).

Pre-operatively, no differences in JPS or sway were found between limbs in either group. No differences existed between the two groups. Post-operatively, both groups had significant improvement of JPS in the operated limb (UKA mean4.64°, SD1.44° and TKA mean5.18°, SD1.35°). No changes in JPS were seen in the control side. A significant improvement (P< 0.0001) in sway area and path was found in the UKA group only in both limbs. No significant changes in sway occurred in either limb of TKA patients. The OKS improved from 21.4 to 35.5 for TKA patients and from 23.9 to 38for UKA patients.

Both UKA and TKA improve proprioception as assessed by JPS. However, UKA alone improves postural sway in both limbs. This may impart explain why UKA patients function better than TKA patients

Introduction: Knee joint arthroplasty (total or unicompartmental) is the standard operative treatment for osteoarthritis (OA). Survival rate is good for both types but functional outcome is different. The function of unicompartmental knee arthroplasty (UKA) is substantially better than that of total knee arthroplasty (TKA). As function can be strongly influenced by proprioceptive ability, it is possible that improved outcome seen in patients with UKA results from retaining proprioceptive function associated with the cruciate ligaments. This prospective longitudinal study aimed to evaluate the change in proprioceptive performance after knee replacement; comparing TKA to UKA.

Methods and Materials: Two groups of patients with OA as diagnosed clinically and by X-ray were recruited. Group 1 consisted of 15 patients (mean age 65.8 years range 57–72 years, 10 females and 5 males) listed for TKA with the AGC prosthesis (Biomet, UK). Group 2 consisted of 19 patients (mean age 65.5 years range 52–75 years; 9 females and 10 males) listed for UKA with the Oxford UKA (Biomet, UK) for medial compartment OA. The ACL and PCL were present and preserved in all patients in Group 2, while only the PCL was preserved in Group 1 patients. Joint Position Sense (JPS) and postural sway were used as measures of proprioception performance. Both groups were assessed pre-and 6 months post-operatively in both limbs. JPS was measured using a dynamometer (KinCom, Chatanooga Ltd) as the error in actively and passively reproducing five randomly ordered knee flexion angles (30°, 40°, 50°, 60° and 70°). Postural sway (area, path and velocity) was measured during single leg stance using a Balance Performance Monitor (SMS Medical) for 30 seconds interval. Functional outcome was assessed using the Oxford Knee Score (OKS).

Results: Pre-operatively, no differences in JPS or sway were found between limbs in either group. No differences existed between the two groups. Post-operatively, both groups had significant improvement of JPS in the operated limb only (Mean ± standard deviation for UKA 4.64±1.44° and for TKA 5.18±1.35°). No changes in JPS were seen in the control side. An improvement in sway was found in the UKA group only. UKA patients showed significant improvement in both sway area and path (p< .0001) for both limbs post-operatively. No significant post-operative changes in sway occurred in either limb of TKA patients. The OKS improved postoperatively in both groups, rising from 21.4 to 35.5 for TKA patients and from 23.9 to 38 for UKA patients.

Conclusion: Interestingly, joint position sense improved for both groups but did not seem to show any difference between UKA and TKA. Postural sway was influenced by joint replacement type. Ligament retention may contribute to improved global postural control seen after unicompartmental knee arthroplasty and may explain the higher level of function seen in these patients.

Purpose of the study Function is strongly infl uenced by proprioceptive ability, this prospective longitudinal study aimed to evaluate the change in proprioceptive performance after knee replacement; comparing total to unicompartment replacement.

Methods and Results Two groups of patients with OA as diagnosed clinically and by X-ray were recruited. Group 1 consisted of 15 patients (mean age 65.8yrs range 57-72yrs, 10 females & 5 males) listed for Total Knee Arthroplasty (TKA) with the AGC (Biomet, UK). Group 2 consisted of 19 patients (mean age 65.5yrs range 52–75yrs; 9 females & 10 males) listed for Oxford Uni-compartmental Knee Arthroplasty (OUKA) for medial compartment OA. The ACL and PCL were present and preserved in all patients in Group 2, while only the PCL was preserved for Group 1 patients.

Joint Position Sense (JPS) & sway were used as measures of proprioception performance. Both groups were assessed pre- and 6 months post-op. JPS was measured using an isokinetic dynamometer (KinCom, Chatanooga Ltd) as the error in actively and passively reproducing fi ve randomly ordered knee fl exion angles (30°, 40°, 50°, 60° and 70°). Sway (area, path and velocity) was measured during single leg stance using a Balance Performance Monitor (SMS Medical) for 30-second interval. Functional outcome was assessed using the Oxford Knee Score (OKS).

Pre-operatively, no differences in JPS or sway were found between limbs in either group. No differences existed between the two groups.

Post-operatively, both groups had signifi cant improvement of JPS in the operated limb only (Mean ± standard deviation for UKA 4.64±1.44° and for TKA 5.18±1.35°). No changes in JPS were seen in the control side. Group 2 patients showed signifi cant improvement in both sway area and path (p< .0001) for both limbs post-operatively. No signifi cant post-operative changes in sway occurred in either limb of Group 1 patients.

The OKS improved post-operatively in both groups, rising from 21.4 to 35.5 for Group 1 patients and from 23.9 to 38 for Group 2 patients.

Conclusion Interestingly, joint position sense improved for both groups but did not seem to show any difference between UKA and TKA. Postural sway was infl uenced by joint replacement type. Ligament retention may contribute to improved global postural control seen after unicompartmental knee arthroplasty and may explain the higher level of function seen in these patients.