Plain radiographs and MRI play an important role in the diagnosis of intra-articular knee pathology and can be used to guide treatment decisions. These imaging modalities however have several limitations which can lead to misdiagnosis, incorrect treatment decisions, and suboptimal patient care. The gold standard for confirmation of intra-articular knee pathology is formal diagnostic knee arthroscopy. Diagnostic knee arthroscopy must be performed in the operating room under general anesthesia, which adds both risk and cost to the patient. In contrast to formal diagnostic arthroscopy which uses a 4.8mm arthroscope, needle arthroscopy (NA) uses a 1.9mm nano-arthroscope. NA with a nano-arthroscope is a technique which allows direct high quality intra-articular visualization to be obtained without general anesthesia, and can be performed either in the office or the operating room (OR).

One specific application for this technology is in the evaluation of patients who are being considered for either a total knee arthroplasty (TKA) or a unicompartmental knee arthroplasty (UKA). An essential component of the pre-operative work-up is determining if the patient has isolated unicompartmental knee osteoarthritis (OA) or more widespread tricompartmental knee OA. This distinction is essential as each condition is treated differently; isolated unicompartmental knee OA is treated with a UKA while tricompartmental OA is treated with TKA.

Our primary objective is to determine if NA is an effective, safe, and cost effective tool to confirm the presence of unicompartmental OA and thus guide patient management in the decision to perform UKA or TKA.

Disclosure: This study is sponsored by Arthrex Inc, the manufacturer of the NanoScope™ operative arthroscopy imaging system which will be used in the study. Arthrex will provide NanoScope™ supplies only; no direct monetary funding will be provided.

A prospective study of patients being evaluated for UKA/TKA will be performed. The study will include two groups: 1) patients who are diagnosed with isolated unicompartmental knee OA by standard weight bearing radiographs and are likely indicated for UKA and 2) patients for whom the standard weight bearing radiographs are equivocal for the diagnosis of unicompartmental OA vs. tricompartmental OA. The preoperative radiographic evaluation prior to UKA or TKA includes a series of standard weight bearing knee radiographs which historically have been used to differentiate between unicompartmental OA and tricompartmental OA. This series of radiographs includes weight bearing AP, lateral, skyline, Rosenberg, and valgus stress views.

Subsequently, after obtaining informed consent, both groups of patients will undergo NA, performing in the operating room on the day of arthroplasty, prior to surgery beginning. NA will be performed with a 1.9mm nano arthroscope, as part of their diagnostic pre-arthroplasty evaluation, in lieu of standard arthroscopy, which utilizes a 4.8mm arthroscope. NA will directly visualize the articular cartilage in the medial, lateral, and patellofemoral compartments of the knee. Cartilage will be arthroscopically graded according to the Outerbridge Classification of chondral lesions. Patients with visualized Grade IV full-thickness cartilage loss with exposed subchondral bone isolated to either the medial or lateral compartment, with Grade 0-II lesions in the contralateral and / or patellofemoral compartments, will undergo a medial or lateral UKA, respectively. Patients with a Grade IV lesion in the medial or lateral compartment, with asymptomatic Grade III lesions in the contralateral and / or patellofemoral compartments will undergo a medial or lateral UKA, respectively. Patients with a Grade IV lesion in the medial or lateral compartment, with symptomatic Grade III lesions in the contralateral and / or patellofemoral compartments will undergo TKA. Patients with a Grade IV lesion in the medial or lateral compartment, with Grade IV lesions in the contralateral and / or patellofemoral compartments will undergo TKA.

Intraoperative findings at the time of arthroplasty will serve at the gold standard to which the NA findings will be compared. Furthermore, the diagnosis obtained from NA will be compared to the diagnosis obtained from preoperative weight bearing radiographs.

Inclusion Criteria:

• English fluency and literacy
• Able to provide informed consent
• Males or females, > 18 years of age and < 89
• Indicated for unicompartmental knee arthroplasty based on a series of existing weight bearing knee plain radiographs
• Have equivocal weight bearing knee radiographs, in which the indication for UKA vs. TKA is not clear
• Meet the following criteria: no inflammatory arthritis, intact Anterior cruciate ligament, no fixed varus deformity > 10 degrees, no fixed valgus deformity > 5 degrees, knee range of motion > 90 degrees, no patellofemoral arthritis

Exclusion Criteria:

• Males or females < 18 years of age and >89
• Prisoners
• Patient who have existing radiographic evidence of tricompartmental OA
• Patients with inflammatory arthritis, anterior cruciate ligament deficiency, fixed varus deformity > 10 degrees, fixed valgus deformity > 5 degrees, knee range of motion < 90 degrees, patellofemoral arthritis