How to manage a native stiff knee

Key points

Overview

This EFORT Open Reviews instructional lecture is a narrative review of the native stiff knee, a condition far less studied than stiffness after surgery, covering its definition, classification, risk factors and treatment, with emphasis on TKA. The authors describe it as rare but disabling and conclude that it needs a customized, stepwise approach. It is a review, not a graded guideline.

Definition and types

Some authors instead define stiffness as flexion limited to 75–90° or a flexion contracture of more than 10°. About 125° of flexion is considered adequate for daily activities including squatting, whereas flexion below 90° affects daily life. Flexion contracture is mainly due to posterior impingement, retraction of anterior structures or patella baja. Stiff knee and arthrofibrosis are often used interchangeably but differ: arthrofibrosis is excessive scar tissue in at least one knee compartment, reported in up to 4% of patients after ACL reconstruction and up to 23% after reconstruction of two or more ligaments.

Risk factors and assessment

Half of patients with severe hemophilia have a knee flexion contracture. Stiffness after septic arthritis affects flexion more than extension. In one study of 63 patients with tibial plateau fractures, 20% had a residual flexion contracture of more than 5° at 12 months, and modern techniques and accelerated rehabilitation have reduced stiffness after ACL reconstruction from 35% to 4%. Assessment starts with clinical examination of active and passive ROM, patellar mobility and the extensor apparatus, with standard X-rays routinely; there is no evidence for routine MRI, which can help after ACL reconstruction.

Release procedures

MUA is now performed less often because of the risk of fractures and tendon rupture; in a study of patients with hemophilia, a single MUA corrected the deformity by a mean of 22°, and the authors of that study suggested repeating it up to three times until the flexion contracture was below 10°. Arthroscopic release is considered after a failed MUA or for stiffness established for at least 3 months, and works better for extension deficit than for flexion contracture. Open release remains an option for severe stiffness or when the posterior capsule must be released.

Knee arthroplasty in the stiff knee

Preoperative ROM strongly predicts postoperative ROM; in one series, patients with preoperative flexion below 77° reached a mean of 93°. A posterior stabilized implant is usually enough, with more constrained implants if instability remains after major releases. With previous scars, the most lateral incision is used, keeping at least 7 cm between incisions. Tibial tubercle osteotomy, 7–10 cm long and 1 cm thick, is the authors' preferred extensile approach; a systematic review reported complication rates of 3.8–20%. Studies report an average ROM improvement of about 40°, and one series had an 18.5% revision rate.

Frequently asked questions

Is a stiff knee the same as arthrofibrosis?

No. A stiff knee is defined by reduced range of motion, while arthrofibrosis is an excessive accumulation of scar tissue in the joint, triggered by trauma, surgery or infection; the terms are often confused.

Is arthroscopic or open release preferred?

Arthroscopy is now the first treatment choice; open release is still considered for severe stiffness and when the posterior capsule must be released.

What can be expected from knee replacement in a stiff knee?

Studies report an average ROM gain of about 40°, but improvements are lower and complication rates higher than in standard TKA.

Source

Pirato F, Rosso F, Dettoni F, Bonasia DE, Bruzzone M, Rossi R. How to manage a native stiff knee. EFORT Open Rev 2024;9(5):363-374. doi:10.1530/EOR-24-0034. Open access. Summary prepared by Medpresso from the original publication; it is not a substitute for the full text or for medical advice.