Abnormal loading of the major joints in knee osteoarthritis and the response to knee replacement

Knee osteoarthritis is common and patients frequently complain that they are ‘overloading’ the joints of the opposite leg when they walk. However, it is unknown whether moments or co-contractions are abnormal in the unaffected joints of patients with single joint knee osteoarthritis, or how they change following treatment of the affected knee. Twenty patients with single joint medial compartment knee osteoarthritis were compared to 20 asymptomatic control subjects. Gait analysis was performed for normal level gait and surface EMG recordings of the medial and lateral quadriceps and hamstrings were used to investigate co-contraction. Patients were followed up 12 months post-operatively and the analysis was repeated. Results are presented for the first 14 patients who have attended follow-up. Pre-operatively, adduction moment impulses were elevated at both knees and the contra-lateral hip compared to controls. Co-contraction of hamstrings and quadriceps was elevated bilaterally. Post-operatively, moment waveforms returned to near-normal levels at the affected knee and co-contraction fell in the majority of patients. However, abnormalities persisted in the contra-lateral limb with partial or no recovery of both moment waveforms and co-contraction in the majority. Patients with knee osteoarthritis do experience abnormal loads of their major weight bearing joints bilaterally, and abnormalities persist despite treatment of the affected limb. Further treatment may be required if we are to protect the other major joints following joint arthroplasty.

► 14 patients with single joint knee osteoarthritis, pre- and 1 year post-arthroplasty.
► Frontal plane moments and quadriceps/hamstrings co-contraction were measured.
► Adduction moments and co-contraction were increased bilaterally compared to controls.
► Moments and co-contractions normalised at the treated knee but not on the other side.
► Abnormal loading was seen bilaterally, and abnormalities persisted despite treatment.